1 =head1 BackupPC Introduction
3 This documentation describes BackupPC version __VERSION__,
4 released on __RELEASEDATE__.
8 BackupPC is a high-performance, enterprise-grade system for backing up
9 Linux and WinXX PCs, desktops and laptops to a server's disk. BackupPC
10 is highly configurable and easy to install and maintain.
12 Given the ever decreasing cost of disks and raid systems, it is now
13 practical and cost effective to backup a large number of machines onto a
14 server's local disk or network storage. For some sites this might be
15 the complete backup solution. For other sites additional permanent
16 archives could be created by periodically backing up the server to tape.
24 A clever pooling scheme minimizes disk storage and disk I/O.
25 Identical files across multiple backups of the same or different PC
26 are stored only once (using hard links), resulting in substantial
27 savings in disk storage and disk writes.
31 Optional compression provides additional reductions in storage
32 (around 40%). The CPU impact of compression is low since only
33 new files (those not already in the pool) need to be compressed.
37 A powerful http/cgi user interface allows administrators to view log
38 files, configuration, current status and allows users to initiate and
39 cancel backups and browse and restore files from backups.
43 The http/cgi user interface has internationalization (i18n) support,
44 currently providing English, French, German, Spanish and Italian.
48 No client-side software is needed. On WinXX the standard smb
49 protocol is used to extract backup data. On linux or unix clients,
50 rsync or tar (over ssh/rsh/nfs) is used to extract backup data.
51 Alternatively, rsync can also be used on WinXX (using cygwin),
52 and Samba could be installed on the linux or unix client to
57 Flexible restore options. Single files can be downloaded from
58 any backup directly from the CGI interface. Zip or Tar archives
59 for selected files or directories from any backup can also be
60 downloaded from the CGI interface. Finally, direct restore to
61 the client machine (using smb or tar) for selected files or
62 directories is also supported from the CGI interface.
66 BackupPC supports mobile environments where laptops are only
67 intermittently connected to the network and have dynamic IP addresses
68 (DHCP). Configuration settings allow machines connected via slower WAN
69 connections (eg: dial up, DSL, cable) to not be backed up, even if they
70 use the same fixed or dynamic IP address as when they are connected
75 Flexible configuration parameters allow multiple backups to be performed
76 in parallel, specification of which shares to backup, which directories
77 to backup or not backup, various schedules for full and incremental
78 backups, schedules for email reminders to users and so on. Configuration
79 parameters can be set system-wide or also on a per-PC basis.
83 Users are sent periodic email reminders if their PC has not
84 recently been backed up. Email content, timing and policies
89 BackupPC is Open Source software hosted by SourceForge.
99 A full backup is a complete backup of a share. BackupPC can be
100 configured to do a full backup at a regular interval (typically
101 weekly). BackupPC can be configured to keep a certain number
102 of full backups. Exponential expiry is also supported, allowing
103 full backups with various vintages to be kept (for example, a
104 settable number of most recent weekly fulls, plus a settable
105 number of older fulls that are 2, 4, 8, or 16 weeks apart).
107 =item Incremental Backup
109 An incremental backup is a backup of files that have changed (based on their
110 modification time) since the last successful full backup. For SMB and
111 tar, BackupPC backups all files that have changed since one hour prior to the
112 start of the last successful full backup. Rsync is more clever: any files
113 who attributes have changed (ie: uid, gid, mtime, modes, size) since the
114 last full are backed up. Deleted and new files are also detected by
115 Rsync incrementals (SMB and tar are not able to detect deleted files or
116 new files whose modification time is prior to the last full dump.
118 BackupPC can also be configured to keep a certain number of incremental
119 backups, and to keep a smaller number of very old incremental backups.
120 (BackupPC does not support multi-level incremental backups, although it
121 would be easy to do so.)
123 BackupPC's CGI interface "fills-in" incremental backups based on the
124 last full backup, giving every backup a "full" appearance. This makes
125 browsing and restoring backups easier.
129 When a full backup fails or is canceled, and some files have already
130 been backed up, BackupPC keeps a partial backup containing just the
131 files that were backed up successfully. The partial backup is removed
132 when the next successful backup completes, or if another full backup
133 fails resulting in a newer partial backup. A failed full backup
134 that has not backed up any files, or any failed incremental backup,
135 is removed; no partial backup is saved in these cases.
137 The partial backup may be browsed or used to restore files just like
138 a successful full or incremental backup.
140 With the rsync transfer method the partial backup is used to resume
141 the next full backup, avoiding the need to retransfer the file data
142 already in the partial backup.
144 =item Identical Files
146 BackupPC pools identical files using hardlinks. By "identical
147 files" we mean files with identical contents, not necessary the
148 same permissions, ownership or modification time. Two files might
149 have different permissions, ownership, or modification time but
150 will still be pooled whenever the contents are identical. This
151 is possible since BackupPC stores the file meta-data (permissions,
152 ownership, and modification time) separately from the file contents.
156 Based on your site's requirements you need to decide what your backup
157 policy is. BackupPC is not designed to provide exact re-imaging of
158 failed disks. See L<Limitations|limitations> for more information.
159 However, the addition of tar transport for linux/unix clients, plus
160 full support for special file types and unix attributes in v1.4.0
161 likely means an exact image of a linux/unix file system can be made.
163 BackupPC saves backups onto disk. Because of pooling you can relatively
164 economically keep several weeks of old backups.
166 At some sites the disk-based backup will be adequate, without a
167 secondary tape backup. This system is robust to any single failure: if a
168 client disk fails or loses files, the BackupPC server can be used to
169 restore files. If the server disk fails, BackupPC can be restarted on a
170 fresh file system, and create new backups from the clients. The chance
171 of the server disk failing can be made very small by spending more money
172 on increasingly better RAID systems.
174 At other sites a secondary tape backup or cd/dvd will be required. This
175 backup can be done perhaps weekly using the archive function of BackupPC.
183 =item BackupPC home page
185 The BackupPC Open Source project is hosted on SourceForge. The
186 home page can be found at:
188 http://backuppc.sourceforge.net
190 This page has links to the current documentation, the SourceForge
191 project page and general information.
193 =item SourceForge project
195 The SourceForge project page is at:
197 http://sourceforge.net/projects/backuppc
199 This page has links to the current releases of BackupPC.
203 Three BackupPC mailing lists exist for announcements (backuppc-announce),
204 developers (backuppc-devel), and a general user list for support, asking
205 questions or any other topic relevant to BackupPC (backuppc-users).
207 The lists are archived on SourceForge and Gmane. The SourceForge lists
208 are not always up to date and the searching is limited, so Gmane is
209 a good alternative. See:
211 http://news.gmane.org/index.php?prefix=gmane.comp.sysutils.backup.backuppc
212 http://sourceforge.net/mailarchive/forum.php?forum_id=503
214 You can subscribe to these lists by visiting:
216 http://lists.sourceforge.net/lists/listinfo/backuppc-announce
217 http://lists.sourceforge.net/lists/listinfo/backuppc-users
218 http://lists.sourceforge.net/lists/listinfo/backuppc-devel
220 The backuppc-announce list is moderated and is used only for
221 important announcements (eg: new versions). It is low traffic.
222 You only need to subscribe to one of backuppc-announce and
223 backuppc-users: backuppc-users also receives any messages on
226 The backuppc-devel list is only for developers who are working on BackupPC.
227 Do not post questions or support requests there. But detailed technical
228 discussions should happen on this list.
230 To post a message to the backuppc-users list, send an email to
232 backuppc-users@lists.sourceforge.net
234 Do not send subscription requests to this address!
236 =item Other Programs of Interest
238 If you want to mirror linux or unix files or directories to a remote server
239 you should consider rsync, L<http://rsync.samba.org>. BackupPC now uses
240 rsync as a transport mechanism; if you are already an rsync user you
241 can think of BackupPC as adding efficient storage (compression and
242 pooling) and a convenient user interface to rsync.
244 Unison is a utility that can do two-way, interactive, synchronization.
245 See L<http://www.cis.upenn.edu/~bcpierce/unison>.
247 Three popular open source packages that do tape backup are
248 Amanda (L<http://www.amanda.org>),
249 afbackup (L<http://sourceforge.net/projects/afbackup>), and
250 Bacula (L<http://www.bacula.org>).
251 Amanda can also backup WinXX machines to tape using samba.
252 These packages can be used as back ends to BackupPC to backup the
253 BackupPC server data to tape.
255 Various programs and scripts use rsync to provide hardlinked backups.
256 See, for example, Mike Rubel's site (L<http://www.mikerubel.org>),
257 J. W. Schultz's dirvish (L<http://www.pegasys.ws/dirvish>),
258 Ben Escoto's rdiff-backup (L<http://rdiff-backup.stanford.edu>),
259 and John Bowman's rlbackup (L<http://www.math.ualberta.ca/imaging/rlbackup>).
261 BackupPC provides many additional features, such as compressed storage,
262 hardlinking any matching files (rather than just files with the same name),
263 and storing special files without root privileges. But these other scripts
264 provide simple and effective solutions and are worthy of consideration.
270 Here are some ideas for new features that might appear in future
271 releases of BackupPC:
277 Adding hardlink support to rsync. Currently the tar XferMethod
278 correctly saves/restores hardlinks, but rsync does not. Rsync
279 2.6.2 has greatly improved the efficiency of saving hardlink
280 information, so File::RsyncP and BackupPC::Xfer::RsyncFileIO need
281 the corresponding changes. Hardlink support is necessary for
282 doing a bare-metal restore of a *nix system.
286 Adding more complete utf8 support. BackupPC should use utf8 as the
287 native charset for storing file names, and the CGI script should emit
288 utf8 so that the file names can be rendered correctly. Additional
289 configuration parameters should allow you to specify the client Xfer
290 charset (ie: the filcharset delivered by the XferMethod). BackupPC
291 should encode/decode between this charset and utf8 when doing a
292 backup/restore. That way BackupPC can store all files in utf8 no
293 matter what charset is used by the XferMethod to deliver the file
294 names. Secondly, the CGI charset should be configurable (default
295 utf8) and the CGI script BackupPC_Admin should encode the utf8 file
296 names in the desired output charset. Finally, the charset used to
297 deliver file names when restoring individual file names should also
298 be configurable, and again BackupPC_Admin should encode the file
299 names in this charset (again, utf8 default). That should allow the
300 "Save As" IE dialog to default to the correct file name.
304 Adding a trip wire feature for notification when files below certain
305 directories change. For example, if you are backing up a DMZ machine,
306 you could request that you get sent email if any files below /bin,
307 /sbin or /usr change.
311 Allow editing of config parameters via the CGI interface. Users should
312 have permission to edit a subset of the parameters for their clients.
313 Additionally, allow an optional self-service capability so that users
314 can sign up and setup their own clients with no need for IT support.
318 Add backend SQL support for various BackupPC metadata, including
319 configuration parameters, client lists, and backup and restore
320 information. At installation time the backend data engine will
321 be specified (eg: MySQL, ascii text etc).
325 Because of file name mangling (adding "f" to start of each file
326 name) and with pending utf8 changes, BackupPC is not able to
327 store files whose file name length is 255 bytes or greater. The
328 format of the attrib file should be extended so that very long
329 file names (ie: >= 255) are abbreviated on the file system, but
330 the full name is stored in the attrib file. This could also be
331 used to eliminate the leading "f", since that is there to avoid
332 collisions with the attrib file.
336 Adding support for FTP (via Net::FTP) and/or wget (for HTTP and FTP)
337 as additional XferMethods. One question with ftp is whether you can
338 support incrementals. It should be possible. For example, you could
339 use Net::FTP->ls to list each directory, and get the file sizes and
340 mtimes. That would allow incrementals to be supported: only backup
341 the files that have different sizes or mtimes for an incremental.
342 You also need the ls() function to recurse directories. The code
343 would need to be robust to the different formats returned by ls() on
346 For wget there would be a new module called BackupPC::Xfer::Wget that
347 uses wget. Wget can do both http and ftp. Certainly backing up a web
348 site via ftp is better than http, especially when there is active
349 content and not just static pages. But the benefit of supporting http
350 is that you could use it to backup config pages of network hardware
351 (eg: routers etc). So if a router fails you have a copy of the config
352 screens and settings. (And the future tripwire feature on the todo
353 list could tell you if someone messed with the router settings.)
354 Probably the only choice with wget is to fetch all the files
355 (either via ftp or http) into a temporary directory, then run
356 tar on that directory and pipe it into BackupPC_tarExtract.
358 The advantage of using wget is you get both http and ftp.
359 The disadvantage is that you can't support incrementals
360 with wget, but you can with Net::FTP. Also people will
361 find wget harder to configure and run.
365 Replacing smbclient with the perl module FileSys::SmbClient. This
366 gives much more direct control of the smb transfer, allowing
367 incrementals to depend on any attribute change (eg: exist, mtime,
368 file size, uid, gid), and better support for include and exclude.
369 Currently smbclient incrementals only depend upon mtime, so
370 deleted files or renamed files are not detected. FileSys::SmbClient
371 would also allow resuming of incomplete full backups in the
372 same manner as rsync will.
376 Support --listed-incremental or --incremental for tar,
377 so that incrementals will depend upon any attribute change (eg: exist,
378 mtime, file size, uid, gid), rather than just mtime. This will allow
379 tar to be to as capable as FileSys::SmbClient and rsync. This is
380 low priority since rsync is really the preferred method.
384 In addition to allowing a specific backup (incremental or full) to
385 be started from the CGI interface, also allow a "regular" backup
386 to be started. This would behave just like a regular background
387 backup and determine whether a full, incremental or nothing
392 For rysnc (and smb when FileSys::SmbClient is supported, and tar when
393 --listed-incremental is supported) support multi-level incrementals.
394 In fact, since incrementals will now be more "accurate", you could
395 choose to never do full backups (except the first time), or at a
396 minimum do them infrequently: each incremental would depend upon
397 the last, giving a continuous chain of differential backups.
401 Allow diffs between two different backed up files to be displayed.
402 The history feature in 2.1.0 does show files that are the same
403 between backups. Most often we would like to just take the diff of
404 the same host, path and file between different backups, but it would
405 be nice to generalize it to any pair of files (ie: different hosts,
406 backups, paths etc). But I'm not sure how the user interface would
411 More speculative: Storing binary file deltas (in fact, reverse deltas)
412 for files that have the same name as a previous backup, but that aren't
413 already in the pool. This will save storage for things like mailbox
414 files or documents that change slightly between backups. Running some
415 benchmarks on a large pool suggests that the potential savings are
416 around 15-20%, which isn't spectacular, and likely not worth the
417 implementation effort. The program xdelta (v1) on SourceForge (see
418 L<http://sourceforge.net/projects/xdelta>) uses an rsync algorithm for
419 doing efficient binary file deltas. Rather than using an external
420 program, File::RsyncP would eventually get the necessary delta
421 generation code from rsync.
425 Comments and suggestions are welcome.
429 BackupPC is free. I work on BackupPC because I enjoy doing it and I like
430 to contribute to the open source community.
432 BackupPC already has more than enough features for my own needs. The
433 main compensation for continuing to work on BackupPC is knowing that
434 more and more people find it useful. So feedback is certainly
435 appreciated. Even negative feedback is helpful, for example "We
436 evaluated BackupPC but didn't use it because it doesn't ...".
438 Beyond being a satisfied user and telling other people about it, everyone
439 is encouraged to add links to L<http://backuppc.sourceforge.net> (I'll
440 see then via Google) or otherwise publicize BackupPC. Unlike the
441 commercial products in this space, I have a zero budget (in both
442 time and money) for marketing, PR and advertising, so it's up to
445 Also, everyone is encouraged to contribute patches, bug reports, feature
446 and design suggestions, new code, and documentation corrections or
449 =head1 Installing BackupPC
459 A linux, solaris, or unix based server with a substantial amount of free
460 disk space (see the next section for what that means). The CPU and disk
461 performance on this server will determine how many simultaneous backups
462 you can run. You should be able to run 4-8 simultaneous backups on a
463 moderately configured server.
465 When BackupPC starts with an empty pool, all the backup data will be
466 written to the pool on disk. After more backups are done, a higher
467 percentage of incoming files will already be in the pool. BackupPC is
468 able to avoid writing to disk new files that are already in the pool.
469 So over time disk writes will reduce significantly (by perhaps a factor
470 of 20 or more), since eventually 95% or more of incoming backup files
471 are typically in the pool. Disk reads from the pool are still needed to
472 do file compares to verify files are an exact match. So, with a mature
473 pool, if a relatively fast client generates data at say 1MB/sec, and you
474 run 4 simultaneous backups, there will be an average server disk load of
475 about 4MB/sec reads and 0.2MB/sec writes (assuming 95% of the incoming
476 files are in the pool). These rates will be perhaps 40% lower if
481 Perl version 5.6.0 or later. BackupPC has been tested with
482 version 5.6.0, 5.6.1, 5.8.0, 5.8.1 and 5.8.2. If you don't
483 have perl, please see L<http://www.cpan.org>.
487 Perl modules Compress::Zlib, Archive::Zip and File::RsyncP. Try "perldoc
488 Compress::Zlib" and "perldoc Archive::Zip" to see if you have these
489 modules. If not, fetch them from L<http://www.cpan.org> and see the
490 instructions below for how to build and install them.
492 The File::RsyncP module is available from L<http://perlrsync.sourceforge.net>
493 or CPAN. You'll need to install the File::RsyncP module if you want to use
494 Rsync as a transport method.
498 If you are using smb to backup WinXX machines you need smbclient and
499 nmblookup from the samba package. You will also need nmblookup if
500 you are backing up linux/unix DHCP machines. See L<http://www.samba.org>.
501 Version 2.2.0 or later of Samba is required (smbclient's tar feature in
502 2.0.8 and prior has bugs for file path lengths around 100 characters
503 and generates bad output when file lengths change during the backup).
504 Samba versions 3.x are stable and recommended instead of 2.x.
506 See L<http://www.samba.org> for source and binaries. It's pretty easy to
507 fetch and compile samba, and just grab smbclient and nmblookup, without
508 doing the installation. Alternatively, L<http://www.samba.org> has binary
509 distributions for most platforms.
513 If you are using tar to backup linux/unix machines you should have version
514 1.13.7 at a minimum, with version 1.13.20 or higher recommended. Use
515 "tar --version" to check your version. Various GNU mirrors have the newest
516 versions of tar, see for example L<http://www.funet.fi/pub/gnu/alpha/gnu/tar>.
517 As of June 2003 the latest version is 1.13.25.
521 If you are using rsync to backup linux/unix machines you should have
522 version 2.5.5 or higher on each client machine. See
523 L<http://rsync.samba.org>. Use "rsync --version" to check your version.
525 For BackupPC to use Rsync you will also need to install the perl
526 File::RsyncP module, which is available from
527 L<http://perlrsync.sourceforge.net>.
528 Version 0.51 or later is required.
532 The Apache web server, see L<http://www.apache.org>, preferably built
533 with mod_perl support.
537 =head2 How much disk space do I need?
539 Here's one real example for an environment that is backing up 65 laptops
540 with compression off. Each full backup averages 3.2GB. Each incremental
541 backup averages about 0.2GB. Storing one full backup and two incremental
542 backups per laptop is around 240GB of raw data. But because of the
543 pooling of identical files, only 87GB is used. This is without
546 Another example, with compression on: backing up 95 laptops, where
547 each backup averages 3.6GB and each incremental averages about 0.3GB.
548 Keeping three weekly full backups, and six incrementals is around
549 1200GB of raw data. Because of pooling and compression, only 150GB
552 Here's a rule of thumb. Add up the C drive usage of all the machines you
553 want to backup (210GB in the first example above). This is a rough
554 minimum space estimate that should allow a couple of full backups and at
555 least half a dozen incremental backups per machine. If compression is on
556 you can reduce the storage requirements by maybe 30-40%. Add some margin
557 in case you add more machines or decide to keep more old backups.
559 Your actual mileage will depend upon the types of clients, operating
560 systems and applications you have. The more uniform the clients and
561 applications the bigger the benefit from pooling common files.
563 For example, the Eudora email tool stores each mail folder in a separate
564 file, and attachments are extracted as separate files. So in the sadly
565 common case of a large attachment emailed to many recipients, Eudora
566 will extract the attachment into a new file. When these machines are
567 backed up, only one copy of the file will be stored on the server, even
568 though the file appears in many different full or incremental backups. In
569 this sense Eudora is a "friendly" application from the point of view of
570 backup storage requirements.
572 An example at the other end of the spectrum is Outlook. Everything
573 (email bodies, attachments, calendar, contact lists) is stored in a
574 single file, which often becomes huge. Any change to this file requires
575 a separate copy of the file to be saved during backup. Outlook is even
576 more troublesome, since it keeps this file locked all the time, so it
577 cannot be read by smbclient whenever Outlook is running. See the
578 L<Limitations|limitations> section for more discussion of this problem.
580 In addition to total disk space, you shold make sure you have
581 plenty of inodes on your BackupPC data partition. Some users have
582 reported running out of inodes on their BackupPC data partition.
583 So even if you have plenty of disk space, BackupPC will report
584 failures when the inodes are exhausted. This is a particular
585 problem with ext2/ext3 file systems that have a fixed number of
586 inodes when the file system is built. Use "df -i" to see your
589 =head2 Step 1: Getting BackupPC
591 Download the latest version from L<http://backuppc.sourceforge.net>.
593 =head2 Step 2: Installing the distribution
595 First off, there are three perl modules you should install.
596 These are all optional, but highly recommended:
602 To enable compression, you will need to install Compress::Zlib
603 from L<http://www.cpan.org>.
604 You can run "perldoc Compress::Zlib" to see if this module is installed.
608 To support restore via Zip archives you will need to install
609 Archive::Zip, also from L<http://www.cpan.org>.
610 You can run "perldoc Archive::Zip" to see if this module is installed.
614 To use rsync and rsyncd with BackupPC you will need to install File::RsyncP.
615 You can run "perldoc File::RsyncP" to see if this module is installed.
616 File::RsyncP is available from L<http://perlrsync.sourceforge.net>.
617 Version 0.51 or later is required.
621 To build and install these packages, fetch the tar.gz file and
622 then run these commands:
624 tar zxvf Archive-Zip-1.01.tar.gz
631 The same sequence of commands can be used for each module.
633 Now let's move onto BackupPC itself. After fetching
634 BackupPC-__VERSION__.tar.gz, run these commands as root:
636 tar zxf BackupPC-__VERSION__.tar.gz
637 cd BackupPC-__VERSION__
640 The configure.pl also accepts command-line options if you wish
641 to run it in a non-interactive manner. It has self-contained
642 documentation for all the command-line options, which you can
647 When you run configure.pl you will be prompted for the full paths
648 of various executables, and you will be prompted for the following
655 It is best if BackupPC runs as a special user, eg backuppc, that has
656 limited privileges. It is preferred that backuppc belongs to a system
657 administrator group so that sys admin members can browse backuppc files,
658 edit the configuration files and so on. Although configurable, the
659 default settings leave group read permission on pool files, so make
660 sure the BackupPC user's group is chosen restrictively.
662 On this installation, this is __BACKUPPCUSER__.
666 You need to decide where to put the data directory, below which
667 all the BackupPC data is stored. This needs to be a big file system.
669 On this installation, this is __TOPDIR__.
671 =item Install Directory
673 You should decide where the BackupPC scripts, libraries and documentation
674 should be installed, eg: /opt/local/BackupPC.
676 On this installation, this is __INSTALLDIR__.
678 =item CGI bin Directory
680 You should decide where the BackupPC CGI script resides. This will
681 usually below Apache's cgi-bin directory.
683 On this installation, this is __CGIDIR__.
685 =item Apache image directory
687 A directory where BackupPC's images are stored so that Apache can
688 serve them. This should be somewhere under Apache's DocumentRoot
693 =head2 Step 3: Setting up config.pl
695 After running configure.pl, browse through the config file,
696 __INSTALLDIR__/conf/config.pl, and make sure all the default settings
697 are correct. In particular, you will need to decide whether to use
698 smb or tar transport (or whether to set it on a per-PC basis),
699 set the smb share password (if using smb), set the backup policies
700 and modify the email message headers and bodies.
702 BackupPC needs to know the smb share user name and password for each PC
703 that uses smb (ie: all the WinXX clients). The user name is specified
704 in $Conf{SmbShareUserName}. There are four ways to tell BackupPC the smb
711 As an environment variable BPC_SMB_PASSWD set before BackupPC starts.
712 If you start BackupPC manually the BPC_SMB_PASSWD variable must be set
713 manually first. For backward compatibility for v1.5.0 and prior, the
714 environment variable PASSWD can be used if BPC_SMB_PASSWD is not set.
715 Warning: on some systems it is possible to see environment variables of
720 Alternatively the BPC_SMB_PASSWD setting can be included in
721 /etc/init.d/backuppc, in which case you must make sure this file
722 is not world (other) readable.
726 As a configuration variable $Conf{SmbSharePasswd} in
727 __TOPDIR__/conf/config.pl. If you put the password
728 here you must make sure this file is not world (other) readable.
732 As a configuration variable $Conf{SmbSharePasswd} in the per-PC
733 configuration file, __TOPDIR__/pc/$host/config.pl. You will have to
734 use this option if the smb share password is different for each host.
735 If you put the password here you must make sure this file is not
736 world (other) readable.
740 Placement and protection of the smb share password is a possible
741 security risk, so please double-check the file and directory
742 permissions. In a future version there might be support for
743 encryption of this password, but a private key will still have to
744 be stored in a protected place. Suggestions are welcome.
746 =head2 Step 4: Setting up the hosts file
748 The file __TOPDIR__/conf/hosts contains the list of clients to backup.
749 BackupPC reads this file in three cases:
759 When BackupPC is sent a HUP (-1) signal. Assuming you installed the
760 init.d script, you can also do this with "/etc/init.d/backuppc reload".
764 When the modification time of the hosts file changes. BackupPC
765 checks the modification time once during each regular wakeup.
769 Whenever you change the hosts file (to add or remove a host) you can
770 either do a kill -HUP BackupPC_pid or simply wait until the next regular
773 Each line in the hosts file contains three fields, separated
780 This is typically the host name or NetBios name of the client machine
781 and should be in lower case. The host name can contain spaces (escape
782 with a backslash), but it is not recommended.
784 Please read the section L<How BackupPC Finds Hosts|how backuppc finds hosts>.
786 In certain cases you might want several distinct clients to refer
787 to the same physical machine. For example, you might have a database
788 you want to backup, and you want to bracket the backup of the database
789 with shutdown/restart using $Conf{DumpPreUserCmd} and $Conf{DumpPostUserCmd}.
790 But you also want to backup the rest of the machine while the database
791 is still running. In the case you can specify two different clients in
792 the host file, using any mnemonic name (eg: myhost_mysql and myhost), and
793 use $Conf{ClientNameAlias} in myhost_mysql's config.pl to specify the
794 real host name of the machine.
798 Starting with v2.0.0 the way hosts are discovered has changed and now
799 in most cases you should specify 0 for the DHCP flag, even if the host
800 has a dynamically assigned IP address.
801 Please read the section L<How BackupPC Finds Hosts|how backuppc finds hosts>
802 to understand whether you need to set the DHCP flag.
804 You only need to set DHCP to 1 if your client machine doesn't
805 respond to the NetBios multicast request:
809 but does respond to a request directed to its IP address:
813 If you do set DHCP to 1 on any client you will need to specify the range of
814 DHCP addresses to search is specified in $Conf{DHCPAddressRanges}.
816 Note also that the $Conf{ClientNameAlias} feature does not work for
817 clients with DHCP set to 1.
821 This should be the unix login/email name of the user who "owns" or uses
822 this machine. This is the user who will be sent email about this
823 machine, and this user will have permission to stop/start/browse/restore
824 backups for this host. Leave this blank if no specific person should
825 receive email or be allowed to stop/start/browse/restore backups
826 for this host. Administrators will still have full permissions.
830 Additional user names, separate by commas and with no white space,
831 can be specified. These users will also have full permission in
832 the CGI interface to stop/start/browse/restore backups for this host.
833 These users will not be sent email about this host.
837 The first non-comment line of the hosts file is special: it contains
838 the names of the columns and should not be edited.
840 Here's a simple example of a hosts file:
842 host dhcp user moreUsers
843 farside 0 craig jim,dave
846 =head2 Step 5: Client Setup
848 Two methods for getting backup data from a client are supported: smb and
849 tar. Smb is the preferred method for WinXX clients and tar is preferred
850 method for linux/unix clients.
852 The transfer method is set using the $Conf{XferMethod} configuration
853 setting. If you have a mixed environment (ie: you will use smb for some
854 clients and tar for others), you will need to pick the most common
855 choice for $Conf{XferMethod} for the main config.pl file, and then
856 override it in the per-PC config file for those hosts that will use
857 the other method. (Or you could run two completely separate instances
858 of BackupPC, with different data directories, one for WinXX and the
859 other for linux/unix, but then common files between the different
860 machine types will duplicated.)
862 Here are some brief client setup notes:
868 The preferred setup for WinXX clients is to set $Conf{XferMethod} to "smb".
869 (Actually, for v2.0.0, rsyncd is the better method for WinXX if you are
870 prepared to run rsync/cygwin on your WinXX client. More information
871 about this will be provided via the FAQ.)
873 If you want to use rsyncd for WinXX clients you can find a pre-packaged
874 zip file on L<http://backuppc.sourceforge.net>. The package is called
875 cygwin-rsync. It contains rsync.exe, template setup files and the
876 minimal set of cygwin libraries for everything to run. The README file
877 contains instructions for running rsync as a service, so it starts
878 automatically everytime you boot your machine.
880 If you build your own rsync, for rsync 2.6.2 it is strongly
881 recommended you apply the patch in the cygwin-rsync package on
882 L<http://backuppc.sourceforge.net>. This patch adds the --checksum-seed
883 option for checksum caching, and also sends all errors to the client,
884 which is important so BackupPC can log all file access errors.
886 Otherwise, to use SMB, you need to create shares for the data you want
887 to backup. Open "My Computer", right click on the drive (eg: C), and
888 select "Sharing..." (or select "Properties" and select the "Sharing"
889 tab). In this dialog box you can enable sharing, select the share name
890 and permissions. Many machines will be configured by default to share
891 the entire C drive as C$ using the administrator password.
893 If this machine uses DHCP you will also need to make sure the
894 NetBios name is set. Go to Control Panel|System|Network Identification
895 (on Win2K) or Control Panel|System|Computer Name (on WinXP).
896 Also, you should go to Control Panel|Network Connections|Local Area
897 Connection|Properties|Internet Protocol (TCP/IP)|Properties|Advanced|WINS
898 and verify that NetBios is not disabled.
900 As an alternative to setting $Conf{XferMethod} to "smb" (using
901 smbclient) for WinXX clients, you can use an smb network filesystem (eg:
902 ksmbfs or similar) on your linux/unix server to mount the share,
903 and then set $Conf{XferMethod} to "tar" (use tar on the network
904 mounted file system).
906 Also, to make sure that file names with 8-bit characters are correctly
907 transferred by smbclient you should add this to samba's smb.conf file
911 # Accept the windows charset
912 client code page = 850
913 character set = ISO8859-1
915 For samba 3.x this should instead be:
918 unix charset = ISO8859-1
920 This setting should work for western europe.
921 See L<http://www.oreilly.com/catalog/samba/chapter/book/ch08_03.html>
922 for more information about settings for other languages.
926 The preferred setup for linux/unix clients is to set $Conf{XferMethod}
927 to "rsync", "rsyncd" or "tar".
929 You can use either rsync, smb, or tar for linux/unix machines. Smb requires
930 that the Samba server (smbd) be run to provide the shares. Since the smb
931 protocol can't represent special files like symbolic links and fifos,
932 tar and rsync are the better transport methods for linux/unix machines.
933 (In fact, by default samba makes symbolic links look like the file or
934 directory that they point to, so you could get an infinite loop if a
935 symbolic link points to the current or parent directory. If you really
936 need to use Samba shares for linux/unix backups you should turn off the
937 "follow symlinks" samba config setting. See the smb.conf manual page.)
939 The requirements for each Xfer Method are:
945 You must have GNU tar on the client machine. Use "tar --version"
946 or "gtar --version" to verify. The version should be at least
947 1.13.7, and 1.13.20 or greater is recommended. Tar is run on
948 the client machine via rsh or ssh.
950 The relevant configuration settings are $Conf{TarClientPath},
951 $Conf{TarShareName}, $Conf{TarClientCmd}, $Conf{TarFullArgs},
952 $Conf{TarIncrArgs}, and $Conf{TarClientRestoreCmd}.
956 You should have at least rsync 2.5.5, and the latest version 2.5.6
957 is recommended. Rsync is run on the remote client via rsh or ssh.
959 The relevant configuration settings are $Conf{RsyncClientPath},
960 $Conf{RsyncClientCmd}, $Conf{RsyncClientRestoreCmd}, $Conf{RsyncShareName},
961 $Conf{RsyncArgs}, and $Conf{RsyncRestoreArgs}.
965 You should have at least rsync 2.5.5, and the latest version 2.5.6
966 is recommended. In this case the rsync daemon should be running on
967 the client machine and BackupPC connects directly to it.
969 The relevant configuration settings are $Conf{RsyncdClientPort},
970 $Conf{RsyncdUserName}, $Conf{RsyncdPasswd}, $Conf{RsyncdAuthRequired},
971 $Conf{RsyncShareName}, $Conf{RsyncArgs}, and $Conf{RsyncRestoreArgs}.
972 $Conf{RsyncShareName} is the name of an rsync module (ie: the thing
973 in square brackets in rsyncd's conf file -- see rsyncd.conf), not a
976 Be aware that rsyncd will remove the leading '/' from path names in
977 symbolic links if you specify "use chroot = no" in the rsynd.conf file.
978 See the rsyncd.conf manual page for more information.
982 For linux/unix machines you should not backup "/proc". This directory
983 contains a variety of files that look like regular files but they are
984 special files that don't need to be backed up (eg: /proc/kcore is a
985 regular file that contains physical memory). See $Conf{BackupFilesExclude}.
986 It is safe to back up /dev since it contains mostly character-special
987 and block-special files, which are correctly handed by BackupPC
988 (eg: backing up /dev/hda5 just saves the block-special file information,
989 not the contents of the disk).
991 Alternatively, rather than backup all the file systems as a single
992 share ("/"), it is easier to restore a single file system if you backup
993 each file system separately. To do this you should list each file system
994 mount point in $Conf{TarShareName} or $Conf{RsyncShareName}, and add the
995 --one-file-system option to $Conf{TarClientCmd} or add --one-file-system
996 (note the different punctuation) to $Conf{RsyncArgs}. In this case there
997 is no need to exclude /proc explicitly since it looks like a different
1000 Next you should decide whether to run tar over ssh, rsh or nfs. Ssh is
1001 the preferred method. Rsh is not secure and therefore not recommended.
1002 Nfs will work, but you need to make sure that the BackupPC user (running
1003 on the server) has sufficient permissions to read all the files below
1006 Ssh allows BackupPC to run as a privileged user on the client (eg:
1007 root), since it needs sufficient permissions to read all the backup
1008 files. Ssh is setup so that BackupPC on the server (an otherwise low
1009 privileged user) can ssh as root on the client, without being prompted
1010 for a password. There are two common versions of ssh: v1 and v2. Here
1011 are some instructions for one way to setup ssh. (Check which version
1012 of SSH you have by typing "ssh" or "man ssh".)
1016 In general this should be similar to Linux/Unix machines.
1020 =item OpenSSH Instructions
1022 Depending upon your OpenSSH installation, many of these steps can be
1023 replaced by running the scripts ssh-user-config and ssh-host-config
1024 included with OpenSSH. You still need to manually exchange the keys.
1028 =item Key generation
1030 As root on the client machine, use ssh-keygen to generate a
1031 public/private key pair, without a pass-phrase:
1033 ssh-keygen -t rsa -N ''
1035 This will save the public key in ~/.ssh/id_rsa.pub and the private
1036 key in ~/.ssh/id_rsa.
1038 =item BackupPC setup
1040 Repeat the above steps for the BackupPC user (__BACKUPPCUSER__) on the server.
1041 Make a copy of the public key to make it recognizable, eg:
1043 ssh-keygen -t rsa -N ''
1044 cp ~/.ssh/id_rsa.pub ~/.ssh/BackupPC_id_rsa.pub
1046 See the ssh and sshd manual pages for extra configuration information.
1050 To allow BackupPC to ssh to the client as root, you need to place
1051 BackupPC's public key into root's authorized list on the client.
1052 Append BackupPC's public key (BackupPC_id_rsa.pub) to root's
1053 ~/.ssh/authorized_keys2 file on the client:
1055 touch ~/.ssh/authorized_keys2
1056 cat BackupPC_id_rsa.pub >> ~/.ssh/authorized_keys2
1058 You should edit ~/.ssh/authorized_keys2 and add further specifiers,
1059 eg: from, to limit which hosts can login using this key. For example,
1060 if your BackupPC host is called backuppc.my.com, there should be
1061 one line in ~/.ssh/authorized_keys2 that looks like:
1063 from="backuppc.my.com" ssh-rsa [base64 key, eg: ABwBCEAIIALyoqa8....]
1065 =item Fix permissions
1067 You will probably need to make sure that all the files
1068 in ~/.ssh have no group or other read/write permission:
1070 chmod -R go-rwx ~/.ssh
1072 You should do the same thing for the BackupPC user on the server.
1076 As the BackupPC user on the server, verify that this command:
1078 ssh -l root clientHostName whoami
1084 You might be prompted the first time to accept the client's host key and
1085 you might be prompted for root's password on the client. Make sure that
1086 this command runs cleanly with no prompts after the first time. You
1087 might need to check /etc/hosts.equiv on the client. Look at the
1088 man pages for more information. The "-v" option to ssh is a good way
1089 to get detailed information about what fails.
1093 =item SSH2 Instructions
1097 =item Key generation
1099 As root on the client machine, use ssh-keygen2 to generate a
1100 public/private key pair, without a pass-phrase:
1102 ssh-keygen2 -t rsa -P
1106 ssh-keygen -t rsa -N ''
1108 (This command might just be called ssh-keygen on your machine.)
1110 This will save the public key in /.ssh2/id_rsa_1024_a.pub and the private
1111 key in /.ssh2/id_rsa_1024_a.
1113 =item Identification
1115 Create the identification file /.ssh2/identification:
1117 echo "IdKey id_rsa_1024_a" > /.ssh2/identification
1119 =item BackupPC setup
1121 Repeat the above steps for the BackupPC user (__BACKUPPCUSER__) on the server.
1122 Rename the key files to recognizable names, eg:
1124 ssh-keygen2 -t rsa -P
1125 mv ~/.ssh2/id_rsa_1024_a.pub ~/.ssh2/BackupPC_id_rsa_1024_a.pub
1126 mv ~/.ssh2/id_rsa_1024_a ~/.ssh2/BackupPC_id_rsa_1024_a
1127 echo "IdKey BackupPC_id_rsa_1024_a" > ~/.ssh2/identification
1129 Based on your ssh2 configuration, you might also need to turn off
1130 StrictHostKeyChecking and PasswordAuthentication:
1132 touch ~/.ssh2/ssh2_config
1133 echo "StrictHostKeyChecking ask" >> ~/.ssh2/ssh2_config
1134 echo "PasswordAuthentication no" >> ~/.ssh2/ssh2_config
1138 To allow BackupPC to ssh to the client as root, you need to place
1139 BackupPC's public key into root's authorized list on the client.
1140 Copy BackupPC's public key (BackupPC_id_rsa_1024_a.pub) to the
1141 /.ssh2 directory on the client. Add the following line to the
1142 /.ssh2/authorization file on the client (as root):
1144 touch /.ssh2/authorization
1145 echo "Key BackupPC_id_rsa_1024_a.pub" >> /.ssh2/authorization
1147 =item Fix permissions
1149 You will probably need to make sure that all the files
1150 in ~/.ssh2 have no group or other read/write permission:
1152 chmod -R go-rwx ~/.ssh2
1154 You should do the same thing for the BackupPC user on the server.
1158 As the BackupPC user on the server, verify that this command:
1160 ssh2 -l root clientHostName whoami
1166 You might be prompted the first time to accept the client's host key and
1167 you might be prompted for root's password on the client. Make sure that
1168 this command runs cleanly with no prompts after the first time. You
1169 might need to check /etc/hosts.equiv on the client. Look at the
1170 man pages for more information. The "-v" option to ssh2 is a good way
1171 to get detailed information about what fails.
1175 =item SSH version 1 Instructions
1177 The concept is identical and the steps are similar, but the specific
1178 commands and file names are slightly different.
1180 First, run ssh-keygen on the client (as root) and server (as the BackupPC
1181 user) and simply hit enter when prompted for the pass-phrase:
1185 This will save the public key in /.ssh/identity.pub and the private
1186 key in /.ssh/identity.
1188 Next, append BackupPC's ~/.ssh/identity.pub (from the server) to root's
1189 /.ssh/authorized_keys file on the client. It's a single long line that
1190 you can cut-and-paste with an editor (make sure it remains a single line).
1192 Next, force protocol version 1 by adding:
1196 to BackupPC's ~/.ssh/config on the server.
1198 Next, run "chmod -R go-rwx ~/.ssh" on the server and "chmod -R go-rwx ~/.ssh"
1201 Finally, test using:
1203 ssh -l root clientHostName whoami
1207 Finally, if this machine uses DHCP you will need to run nmbd (the
1208 NetBios name server) from the Samba distribution so that the machine
1209 responds to a NetBios name request. See the manual page and Samba
1210 documentation for more information.
1214 =head2 Step 6: Running BackupPC
1216 The installation contains an init.d backuppc script that can be copied
1217 to /etc/init.d so that BackupPC can auto-start on boot.
1218 See init.d/README for further instructions.
1220 BackupPC should be ready to start. If you installed the init.d script,
1221 then you should be able to run BackupPC with:
1223 /etc/init.d/backuppc start
1225 (This script can also be invoked with "stop" to stop BackupPC and "reload"
1226 to tell BackupPC to reload config.pl and the hosts file.)
1230 __INSTALLDIR__/bin/BackupPC -d
1232 as user __BACKUPPCUSER__. The -d option tells BackupPC to run as a daemon
1233 (ie: it does an additional fork).
1235 Any immediate errors will be printed to stderr and BackupPC will quit.
1236 Otherwise, look in __TOPDIR__/log/LOG and verify that BackupPC reports
1237 it has started and all is ok.
1239 =head2 Step 7: Talking to BackupPC
1241 Note: as of version 1.5.0, BackupPC no longer supports telnet
1242 to its TCP port. First off, a unix domain socket is used
1243 instead of a TCP port. (The TCP port can still be re-enabled
1244 if your installation has apache and BackupPC running on different
1245 machines.) Secondly, even if you still use the TCP port, the
1246 messages exchanged over this interface are now protected by
1247 an MD5 digest based on a shared secret (see $Conf{ServerMesgSecret})
1248 as well as sequence numbers and per-session unique keys, preventing
1249 forgery and replay attacks.
1251 You should verify that BackupPC is running by using BackupPC_serverMesg.
1252 This sends a message to BackupPC via the unix (or TCP) socket and prints
1255 You can request status information and start and stop backups using this
1256 interface. This socket interface is mainly provided for the CGI interface
1257 (and some of the BackupPC sub-programs use it too). But right now we just
1258 want to make sure BackupPC is happy. Each of these commands should
1259 produce some status output:
1261 __INSTALLDIR__/bin/BackupPC_serverMesg status info
1262 __INSTALLDIR__/bin/BackupPC_serverMesg status jobs
1263 __INSTALLDIR__/bin/BackupPC_serverMesg status hosts
1265 The output should be some hashes printed with Data::Dumper. If it
1266 looks cryptic and confusing, and doesn't look like an error message,
1269 The jobs status should initially show just BackupPC_trashClean.
1270 The hosts status should produce a list of every host you have listed
1271 in __TOPDIR__/conf/hosts as part of a big cryptic output line.
1273 You can also request that all hosts be queued:
1275 __INSTALLDIR__/bin/BackupPC_serverMesg backup all
1277 At this point you should make sure the CGI interface works since
1278 it will be much easier to see what is going on. That's our
1281 =head2 Step 8: CGI interface
1283 The CGI interface script, BackupPC_Admin, is a powerful and flexible
1284 way to see and control what BackupPC is doing. It is written for an
1285 Apache server. If you don't have Apache, see L<http://www.apache.org>.
1287 There are two options for setting up the CGI interface: standard
1288 mode and using mod_perl. Mod_perl provides much higher performance
1289 (around 15x) and is the best choice if your Apache was built with
1290 mod_perl support. To see if your apache was built with mod_perl
1293 httpd -l | egrep mod_perl
1295 If this prints mod_perl.c then your Apache supports mod_perl.
1297 Using mod_perl with BackupPC_Admin requires a dedicated Apache
1298 to be run as the BackupPC user (__BACKUPPCUSER__). This is
1299 because BackupPC_Admin needs permission to access various files
1300 in BackupPC's data directories. In contrast, the standard
1301 installation (without mod_perl) solves this problem by having
1302 BackupPC_Admin installed as setuid to the BackupPC user, so that
1303 BackupPC_Admin runs as the BackuPC user.
1305 Here are some specifics for each setup:
1309 =item Standard Setup
1311 The CGI interface should have been installed by the configure.pl script
1312 in __CGIDIR__/BackupPC_Admin. BackupPC_Admin should have been installed
1313 as setuid to the BackupPC user (__BACKUPPCUSER__), in addition to user
1314 and group execute permission.
1316 You should be very careful about permissions on BackupPC_Admin and
1317 the directory __CGIDIR__: it is important that normal users cannot
1318 directly execute or change BackupPC_Admin, otherwise they can access
1319 backup files for any PC. You might need to change the group ownership
1320 of BackupPC_Admin to a group that Apache belongs to so that Apache
1321 can execute it (don't add "other" execute permission!).
1322 The permissions should look like this:
1324 ls -l __CGIDIR__/BackupPC_Admin
1325 -swxr-x--- 1 __BACKUPPCUSER__ web 82406 Jun 17 22:58 __CGIDIR__/BackupPC_Admin
1327 The setuid script won't work unless perl on your machine was installed
1328 with setuid emulation. This is likely the problem if you get an error
1329 saying such as "Wrong user: my userid is 25, instead of 150", meaning
1330 the script is running as the httpd user, not the BackupPC user.
1331 This is because setuid scripts are disabled by the kernel in most
1332 flavors of unix and linux.
1334 To see if your perl has setuid emulation, see if there is a program
1335 called sperl5.6.0 or sperl5.6.1 in the place where perl is installed.
1336 If you can't find this program, then you have two options: rebuild
1337 and reinstall perl with the setuid emulation turned on (answer "y" to
1338 the question "Do you want to do setuid/setgid emulation?" when you
1339 run perl's configure script), or switch to the mod_perl alternative
1340 for the CGI script (which doesn't need setuid to work).
1342 =item Mod_perl Setup
1344 The advantage of the mod_perl setup is that no setuid script is needed,
1345 and there is a huge performance advantage. Not only does all the perl
1346 code need to be parsed just once, the config.pl and hosts files, plus
1347 the connection to the BackupPC server are cached between requests. The
1348 typical speedup is around 15 times.
1350 To use mod_perl you need to run Apache as user __BACKUPPCUSER__.
1351 If you need to run multiple Apache's for different services then
1352 you need to create multiple top-level Apache directories, each
1353 with their own config file. You can make copies of /etc/init.d/httpd
1354 and use the -d option to httpd to point each http to a different
1355 top-level directory. Or you can use the -f option to explicitly
1356 point to the config file. Multiple Apache's will run on different
1357 Ports (eg: 80 is standard, 8080 is a typical alternative port accessed
1358 via http://yourhost.com:8080).
1360 Inside BackupPC's Apache http.conf file you should check the
1361 settings for ServerRoot, DocumentRoot, User, Group, and Port. See
1362 L<http://httpd.apache.org/docs/server-wide.html> for more details.
1364 For mod_perl, BackupPC_Admin should not have setuid permission, so
1365 you should turn it off:
1367 chmod u-s __CGIDIR__/BackupPC_Admin
1369 To tell Apache to use mod_perl to execute BackupPC_Admin, add this
1370 to Apache's 1.x httpd.conf file:
1372 <IfModule mod_perl.c>
1373 PerlModule Apache::Registry
1375 <Location /cgi-bin/BackupPC/BackupPC_Admin> # <--- change path as needed
1376 SetHandler perl-script
1377 PerlHandler Apache::Registry
1383 Apache 2.0.44 with Perl 5.8.0 on RedHat 7.1, Don Silvia reports that
1384 this works (with tweaks from Michael Tuzi):
1386 LoadModule perl_module modules/mod_perl.so
1389 <Directory /path/to/cgi/>
1390 SetHandler perl-script
1391 PerlResponseHandler ModPerl::Registry
1392 PerlOptions +ParseHeaders
1397 Allow from 192.168.0
1398 AuthName "Backup Admin"
1400 AuthUserFile /path/to/user_file
1404 There are other optimizations and options with mod_perl. For
1405 example, you can tell mod_perl to preload various perl modules,
1406 which saves memory compared to loading separate copies in every
1407 Apache process after they are forked. See Stas's definitive
1408 mod_perl guide at L<http://perl.apache.org/guide>.
1412 BackupPC_Admin requires that users are authenticated by Apache.
1413 Specifically, it expects that Apache sets the REMOTE_USER environment
1414 variable when it runs. There are several ways to do this. One way
1415 is to create a .htaccess file in the cgi-bin directory that looks like:
1417 AuthGroupFile /etc/httpd/conf/group # <--- change path as needed
1418 AuthUserFile /etc/http/conf/passwd # <--- change path as needed
1423 You will also need "AllowOverride Indexes AuthConfig" in the Apache
1424 httpd.conf file to enable the .htaccess file. Alternatively, everything
1425 can go in the Apache httpd.conf file inside a Location directive. The
1426 list of users and password file above can be extracted from the NIS
1429 One alternative is to use LDAP. In Apache's http.conf add these lines:
1431 LoadModule auth_ldap_module modules/auth_ldap.so
1432 AddModule auth_ldap.c
1434 # cgi-bin - auth via LDAP (for BackupPC)
1435 <Location /cgi-binBackupPC/BackupPC_Admin> # <--- change path as needed
1437 AuthName "BackupPC login"
1438 # replace MYDOMAIN, PORT, ORG and CO as needed
1439 AuthLDAPURL ldap://ldap.MYDOMAIN.com:PORT/o=ORG,c=CO?uid?sub?(objectClass=*)
1443 If you want to disable the user authentication you can set
1444 $Conf{CgiAdminUsers} to '*', which allows any user to have
1445 full access to all hosts and backups. In this case the REMOTE_USER
1446 environment variable does not have to be set by Apache.
1448 Alternatively, you can force a particular user name by getting Apache
1449 to set REMOTE_USER, eg, to hardcode the user to www you could add
1450 this to Apache's httpd.conf:
1452 <Location /cgi-bin/BackupPC/BackupPC_Admin> # <--- change path as needed
1453 Setenv REMOTE_USER www
1456 Finally, you should also edit the config.pl file and adjust, as necessary,
1457 the CGI-specific settings. They're near the end of the config file. In
1458 particular, you should specify which users or groups have administrator
1459 (privileged) access: see the config settings $Conf{CgiAdminUserGroup}
1460 and $Conf{CgiAdminUsers}. Also, the configure.pl script placed various
1461 images into $Conf{CgiImageDir} that BackupPC_Admin needs to serve
1462 up. You should make sure that $Conf{CgiImageDirURL} is the correct
1463 URL for the image directory.
1465 See the section L<Debugging installation problems|debugging installation problems> for suggestions on debugging the Apache authentication setup.
1467 =head2 How BackupPC Finds Hosts
1469 Starting with v2.0.0 the way hosts are discovered has changed. In most
1470 cases you should specify 0 for the DHCP flag in the conf/hosts file,
1471 even if the host has a dynamically assigned IP address.
1473 BackupPC (starting with v2.0.0) looks up hosts with DHCP = 0 in this manner:
1479 First DNS is used to lookup the IP address given the client's name
1480 using perl's gethostbyname() function. This should succeed for machines
1481 that have fixed IP addresses that are known via DNS. You can manually
1482 see whether a given host have a DNS entry according to perls'
1483 gethostbyname function with this command:
1485 perl -e 'print(gethostbyname("myhost") ? "ok\n" : "not found\n");'
1489 If gethostbyname() fails, BackupPC then attempts a NetBios multicast to
1490 find the host. Provided your client machine is configured properly,
1491 it should respond to this NetBios multicast request. Specifically,
1492 BackupPC runs a command of this form:
1496 If this fails you will see output like:
1498 querying myhost on 10.10.255.255
1499 name_query failed to find name myhost
1501 If this success you will see output like:
1503 querying myhost on 10.10.255.255
1504 10.10.1.73 myhost<00>
1506 Depending on your netmask you might need to specify the -B option to
1507 nmblookup. For example:
1509 nmblookup -B 10.10.1.255 myhost
1511 If necessary, experiment on the nmblookup command that will return the
1512 IP address of the client given its name. Then update
1513 $Conf{NmbLookupFindHostCmd} with any necessary options to nmblookup.
1517 For hosts that have the DHCP flag set to 1, these machines are
1518 discovered as follows:
1524 A DHCP address pool ($Conf{DHCPAddressRanges}) needs to be specified.
1525 BackupPC will check the NetBIOS name of each machine in the range using
1526 a command of the form:
1528 nmblookup -A W.X.Y.Z
1530 where W.X.Y.Z is each candidate address from $Conf{DHCPAddressRanges}.
1531 Any host that has a valid NetBIOS name returned by this command (ie:
1532 matching an entry in the hosts file) will be backed up. You can
1533 modify the specific nmblookup command if necessary via $Conf{NmbLookupCmd}.
1537 You only need to use this DHCP feature if your client machine doesn't
1538 respond to the NetBios multicast request:
1542 but does respond to a request directed to its IP address:
1544 nmblookup -A W.X.Y.Z
1548 =head2 Other installation topics
1552 =item Removing a client
1554 If there is a machine that no longer needs to be backed up (eg: a retired
1555 machine) you have two choices. First, you can keep the backups accessible
1556 and browsable, but disable all new backups. Alternatively, you can
1557 completely remove the client and all its backups.
1559 To disable backups for a client there are two special values for
1560 $Conf{FullPeriod} in that client's per-PC config.pl file:
1566 Don't do any regular backups on this machine. Manually
1567 requested backups (via the CGI interface) will still occur.
1571 Don't do any backups on this machine. Manually requested
1572 backups (via the CGI interface) will be ignored.
1576 This will still allow that client's old backups to be browsable
1579 To completely remove a client and all its backups, you should remove its
1580 entry in the conf/hosts file, and then delete the __TOPDIR__/pc/$host
1581 directory. Whenever you change the hosts file, you should send
1582 BackupPC a HUP (-1) signal so that it re-reads the hosts file.
1583 If you don't do this, BackupPC will automatically re-read the
1584 hosts file at the next regular wakeup.
1586 Note that when you remove a client's backups you won't initially recover
1587 a lot of disk space. That's because the client's files are still in
1588 the pool. Overnight, when BackupPC_nightly next runs, all the unused
1589 pool files will be deleted and this will recover the disk space used
1590 by the client's backups.
1592 =item Copying the pool
1594 If the pool disk requirements grow you might need to copy the entire
1595 data directory to a new (bigger) file system. Hopefully you are lucky
1596 enough to avoid this by having the data directory on a RAID file system
1597 or LVM that allows the capacity to be grown in place by adding disks.
1599 The backup data directories contain large numbers of hardlinks. If
1600 you try to copy the pool the target directory will occupy a lot more
1601 space if the hardlinks aren't re-established.
1603 The GNU cp program with the -a option is aware of hardlinks and knows
1604 to re-establish them. So GNU cp -a is the recommended way to copy
1605 the data directory and pool. Don't forget to stop BackupPC while
1608 =item Compressing an existing pool
1610 If you are upgrading BackupPC and want to turn compression on you have
1617 Simply turn on compression. All new backups will be compressed. Both old
1618 (uncompressed) and new (compressed) backups can be browsed and viewed.
1619 Eventually, the old backups will expire and all the pool data will be
1620 compressed. However, until the old backups expire, this approach could
1621 require 60% or more additional pool storage space to store both
1622 uncompressed and compressed versions of the backup files.
1626 Convert all the uncompressed pool files and backups to compressed.
1627 The script __INSTALLDIR__/bin/BackupPC_compressPool does this.
1628 BackupPC must not be running when you run BackupPC_compressPool.
1629 Also, there must be no existing compressed backups when you
1630 run BackupPC_compressPool.
1632 BackupPC_compressPool compresses all the files in the uncompressed pool
1633 (__TOPDIR__/pool) and moves them to the compressed pool
1634 (__TOPDIR__/cpool). It rewrites the files in place, so that the
1635 existing hardlinks are not disturbed.
1639 The rest of this section discusses how to run BackupPC_compressPool.
1641 BackupPC_compressPool takes three command line options:
1647 Test mode: do everything except actually replace the pool files.
1648 Useful for estimating total run time without making any real
1653 Read check: re-read the compressed file and compare it against
1654 the original uncompressed file. Can only be used in test mode.
1658 Number of children to fork. BackupPC_compressPool can take a long time
1659 to run, so to speed things up it spawns four children, each working on a
1660 different part of the pool. You can change the number of children with
1665 Here are the recommended steps for running BackupPC_compressPool:
1671 Stop BackupPC (eg: "/etc/init.d/backuppc stop").
1675 Set $Conf{CompressLevel} to a non-zero number (eg: 3).
1679 Do a dry run of BackupPC_compressPool. Make sure you run this as
1680 the BackupPC user (__BACKUPPCUSER__):
1682 BackupPC_compressPool -t -r
1684 The -t option (test mode) makes BackupPC_compressPool do all the steps,
1685 but not actually change anything. The -r option re-reads the compressed
1686 file and compares it against the original.
1688 BackupPC_compressPool gives a status as it completes each 1% of the job.
1689 It also shows the cumulative compression ratio and estimated completion
1690 time. Once you are comfortable that things look ok, you can kill
1691 BackupPC_compressPool or wait for it to finish.
1695 Now you are ready to run BackupPC_compressPool for real. Once again,
1696 as the BackupPC user (__BACKUPPCUSER__), run:
1698 BackupPC_compressPool
1700 You should put the output into a file and tail this file. (The running
1701 time could be twice as long as the test mode since the test mode file
1702 writes are immediately followed by an unlink, so in test mode it is
1703 likely the file writes never make it to disk.)
1705 It is B<critical> that BackupPC_compressPool runs to completion before
1706 re-starting BackupPC. Before BackupPC_compressPool completes, none of
1707 the existing backups will be in a consistent state. If you must stop
1708 BackupPC_compressPool for some reason, send it an INT or TERM signal
1709 and give it several seconds (or more) to clean up gracefully.
1710 After that, you can re-run BackupPC_compressPool and it will start
1711 again where it left off. Once again, it is critical that it runs
1716 After BackupPC_compressPool completes you should have a complete set
1717 of compressed backups (and your disk usage should be lower). You
1718 can now re-start BackupPC.
1722 =head2 Debugging installation problems
1724 This section will probably grow based on the types of questions on
1725 the BackupPC mail list. Eventually the FAQ at
1726 L<http://backuppc.sourceforge.net/faq/> will include more details
1731 =item Check log files
1733 Assuming BackupPC can start correctly you should inspect __TOPDIR__/log/LOG
1734 for any errors. Assuming backups for a particular host start, you
1735 should be able to look in __TOPDIR__/pc/$host/LOG for error messages
1736 specific to that host. Always check both log files.
1738 =item CGI script doesn't run
1740 Perhaps the most common program with the installation is getting the
1741 CGI script to run. Often the setuid isn't configured correctly, or
1742 doesn't work on your system.
1744 First, try running BackupPC_Admin manually as the BackupPC user, eg:
1747 __CGIDIR__/BackupPC_Admin
1749 Now try running it as the httpd user (which ever user apache runs as);
1752 __CGIDIR__/BackupPC_Admin
1754 In both cases do you get normal html output?
1756 If the first case works but the second case fails with an error that
1757 the wrong user is running the script then you have a setuid problem.
1758 (This assumes you are running BackupPC_Admin without mod_perl, and
1759 you therefore need seduid to work. If you are using mod_perl then
1760 apache should run as user __BACKUPPCUSER__.)
1762 First you should make sure the cgi-bin directory is on a file system
1763 that doesn't have the "nosuid" mount option.
1765 Next, experiment by creating this script:
1769 printf("My userid is $> (%s)\n", (getpwuid($>))[0]);
1771 then chown it to backuppc and chmod u+s:
1773 root# chown backuppc testsetuid
1774 root# chmod u+s testsetuid
1775 root# chmod a+x testsetuid
1776 root# ls -l testsetuid
1777 -rwsr-xr-x 1 backuppc wheel 76 Aug 26 09:46 testsetuid*
1779 Now run this program as a normal user. What uid does it print?
1780 Try changing the first line of the script to directly call sperl:
1782 #!/usr/bin/sperl5.8.0
1784 (modify according to your version and path). Does this work
1787 Finally, you should invoke the CGI script from a browser, using
1790 http://myHost/cgi-bin/BackupPC/BackupPC_Admin
1792 You should make sure REMOTE_USER is being set by apache (see the
1793 earlier section) so that user authentication works. Make sure
1794 the config settings $Conf{CgiAdminUserGroup} and $Conf{CgiAdminUsers}
1795 correctly specify the privileged administrator users.
1797 =item You cannot access per-host information in the CGI interface
1799 If you get the error
1801 Only privileged users can view information about host xyz
1803 it means that BackupPC_Admin is unable to match the user's login
1804 name (supplied by Apache via the REMOTE_USER environment variable)
1805 with either that host's user name (in the conf/hosts file) or
1806 with the administrators specified in the $Conf{CgiAdminUsers}
1807 or $Conf{CgiAdminUserGroup} settings.
1809 The most common problem is that REMOTE_USER is not set because the
1810 Apache authentication is not correctly configured. In this case
1811 BackupPC_Admin will report this additional error:
1813 Note: $ENV{REMOTE_USER} is not set, which could mean there is an
1814 installation problem. BackupPC_Admin expects Apache to authenticate
1815 the user and pass their user name into this script as the REMOTE_USER
1816 environment variable. See the documentation.
1818 You should review the configuration instructions to setup Apache
1819 authentication correctly. To test if REMOTE_USER is being set
1820 correctly, there is a simple script called printenv that is
1821 included with Apache. This is a simple CGI script that prints
1822 out all the environment variables. Place this script in the
1823 same directory as BackupPC_Admin and run it with a URL like:
1825 http://myHost/cgi-bin/BackupPC/printenv
1827 Check the value of the REMOTE_USER environment variable.
1828 Here's a copy of the printenv script:
1832 ## printenv -- demo CGI program which just prints its environment
1835 print "Content-type: text/plain\n\n";
1836 foreach $var (sort(keys(%ENV))) {
1840 print "${var}=\"${val}\"\n";
1843 =item Can't ping or find host
1845 Please read the section L<How BackupPC Finds Hosts|how backuppc finds hosts>.
1847 The BackupPC_dump command now has a -v option, so the easiest way to
1848 debug backup problems on a specific host is to run BackupPC_dump
1849 manually as the BackupPC user:
1852 __INSTALLDIR__/bin/BackupPC_dump -v -f hostName
1854 This will run a full dump on hostName (replace with your host name).
1855 It will show each command (eg: ping, nmblookup and the full dump
1856 commands) and the output from each command. Reading the output
1857 carefully should show you what the problem is.
1859 You can also verify that nmblookup correctly returns the netbios name.
1860 This is essential for DHCP hosts, and depending upon the setting of
1861 $Conf{FixedIPNetBiosNameCheck} might also be required for fixed IP
1862 address hosts too. Run this command:
1864 nmblookup -A hostName
1866 Verify that the host name is printed. The output might look like:
1869 DELLLS13 <00> - P <ACTIVE>
1870 DOMAINNAME <00> - <GROUP> P <ACTIVE>
1871 DELLLS13 <20> - P <ACTIVE>
1872 DOMAINNAME <1e> - <GROUP> P <ACTIVE>
1873 DELLLS13 <03> - P <ACTIVE>
1874 DELLLS13$ <03> - P <ACTIVE>
1875 CRAIG <03> - P <ACTIVE>
1877 The first name, converted to lower case, is used for the host name.
1879 =item Transport method doesn't work
1881 The BackupPC_dump command has a -v option, so the easiest way to
1882 debug backup problems on a specific host is to run BackupPC_dump
1883 manually as the BackupPC user:
1886 __INSTALLDIR__/bin/BackupPC_dump -v -f hostName
1888 This will run a full dump on hostName (replace with your host name)
1889 and will print all the output from each command, including the log
1892 The most likely problems will relate to connecting to the smb shares on
1893 each host. On each failed backup, a file __TOPDIR__/pc/$host/XferLOG.bad.z
1894 will be created. This is the stderr output from the transport program.
1895 You can view this file via the CGI interface, or manually uncompress it
1898 __INSTALLDIR__/bin/BackupPC_zcat __TOPDIR__/pc/$host/XferLOG.bad.z | more
1900 The first line will show the full command that was run (eg: rsync, tar
1901 or smbclient). Based on the error messages you should figure out what
1902 is wrong. Possible errors on the server side are invalid host, invalid
1903 share name, bad username or password. Possible errors on the client
1904 side are misconfiguration of the share, username or password.
1906 You should try running the command manually to see what happens.
1907 For example, for smbclient you should it manually and verify that
1908 you can connect to the host in interactive mode, eg:
1910 smbclient '\\hostName\shareName' -U userName
1912 shareName should match the $Conf{SmbShareName} setting and userName
1913 should match the the $Conf{SmbShareUserName} setting.
1915 You will be prompted for the password. You should then see this prompt:
1919 Verify that "ls" works and then type "quit" to exit.
1923 =head1 Restore functions
1925 BackupPC supports several different methods for restoring files. The
1926 most convenient restore options are provided via the CGI interface.
1927 Alternatively, backup files can be restored using manual commands.
1929 =head2 CGI restore options
1931 By selecting a host in the CGI interface, a list of all the backups
1932 for that machine will be displayed. By selecting the backup number
1933 you can navigate the shares and directory tree for that backup.
1935 BackupPC's CGI interface automatically fills incremental backups
1936 with the corresponding full backup, which means each backup has
1937 a filled appearance. Therefore, there is no need to do multiple
1938 restores from the incremental and full backups: BackupPC does all
1939 the hard work for you. You simply select the files and directories
1940 you want from the correct backup vintage in one step.
1942 You can download a single backup file at any time simply by selecting
1943 it. Your browser should prompt you with the file name and ask you
1944 whether to open the file or save it to disk.
1946 Alternatively, you can select one or more files or directories in
1947 the currently selected directory and select "Restore selected files".
1948 (If you need to restore selected files and directories from several
1949 different parent directories you will need to do that in multiple
1952 If you select all the files in a directory, BackupPC will replace
1953 the list of files with the parent directory. You will be presented
1954 with a screen that has three options:
1958 =item Option 1: Direct Restore
1960 With this option the selected files and directories are restored
1961 directly back onto the host, by default in their original location.
1962 Any old files with the same name will be overwritten, so use caution.
1963 You can optionally change the target host name, target share name,
1964 and target path prefix for the restore, allowing you to restore the
1965 files to a different location.
1967 Once you select "Start Restore" you will be prompted one last time
1968 with a summary of the exact source and target files and directories
1969 before you commit. When you give the final go ahead the restore
1970 operation will be queued like a normal backup job, meaning that it
1971 will be deferred if there is a backup currently running for that host.
1972 When the restore job is run, smbclient or tar is used (depending upon
1973 $Conf{XferMethod}) to actually restore the files. Sorry, there is
1974 currently no option to cancel a restore that has been started.
1976 A record of the restore request, including the result and list of
1977 files and directories, is kept. It can be browsed from the host's
1978 home page. $Conf{RestoreInfoKeepCnt} specifies how many old restore
1979 status files to keep.
1981 =item Option 2: Download Zip archive
1983 With this option a zip file containing the selected files and directories
1984 is downloaded. The zip file can then be unpacked or individual files
1985 extracted as necessary on the host machine. The compression level can be
1986 specified. A value of 0 turns off compression.
1988 When you select "Download Zip File" you should be prompted where to
1989 save the restore.zip file.
1991 BackupPC does not consider downloading a zip file as an actual
1992 restore operation, so the details are not saved for later browsing
1993 as in the first case. However, a mention that a zip file was
1994 downloaded by a particular user, and a list of the files, does
1995 appear in BackupPC's log file.
1997 =item Option 3: Download Tar archive
1999 This is identical to the previous option, except a tar file is downloaded
2000 rather than a zip file (and there is currently no compression option).
2004 =head2 Command-line restore options
2006 Apart from the CGI interface, BackupPC allows you to restore files
2007 and directories from the command line. The following programs can
2014 For each file name argument it inflates (uncompresses) the file and
2015 writes it to stdout. To use BackupPC_zcat you could give it the
2018 __INSTALLDIR__/bin/BackupPC_zcat __TOPDIR__/pc/host/5/fc/fcraig/fexample.txt > example.txt
2020 It's your responsibility to make sure the file is really compressed:
2021 BackupPC_zcat doesn't check which backup the requested file is from.
2023 =item BackupPC_tarCreate
2025 BackupPC_tarCreate creates a tar file for any files or directories in
2026 a particular backup. Merging of incrementals is done automatically,
2027 so you don't need to worry about whether certain files appear in the
2028 incremental or full backup.
2032 BackupPC_tarCreate [-t] [-h host] [-n dumpNum] [-s shareName]
2033 [-r pathRemove] [-p pathAdd]
2034 files/directories...
2036 The command-line files and directories are relative to the specified
2037 shareName. The tar file is written to stdout.
2039 The required options are:
2045 host from which the tar archive is created
2049 dump number from which the tar archive is created
2053 share name from which the tar archive is created
2063 print summary totals
2067 path prefix that will be replaced with pathAdd
2075 The -h, -n and -s options specify which dump is used to generate
2076 the tar archive. The -r and -p options can be used to relocate
2077 the paths in the tar archive so extracted files can be placed
2078 in a location different from their original location.
2080 =item BackupPC_zipCreate
2082 BackupPC_zipCreate creates a zip file for any files or directories in
2083 a particular backup. Merging of incrementals is done automatically,
2084 so you don't need to worry about whether certain files appear in the
2085 incremental or full backup.
2089 BackupPC_zipCreate [-t] [-h host] [-n dumpNum] [-s shareName]
2090 [-r pathRemove] [-p pathAdd] [-c compressionLevel]
2091 files/directories...
2093 The command-line files and directories are relative to the specified
2094 shareName. The zip file is written to stdout.
2096 The required options are:
2102 host from which the zip archive is created
2106 dump number from which the zip archive is created
2110 share name from which the zip archive is created
2120 print summary totals
2124 path prefix that will be replaced with pathAdd
2132 compression level (default is 0, no compression)
2136 The -h, -n and -s options specify which dump is used to generate
2137 the zip archive. The -r and -p options can be used to relocate
2138 the paths in the zip archive so extracted files can be placed
2139 in a location different from their original location.
2143 Each of these programs reside in __INSTALLDIR__/bin.
2145 =head1 Archive functions
2147 BackupPC supports archiving to removable media. For users that require
2148 offsite backups, BackupPC can create archives that stream to tape
2149 devices, or create files of specified sizes to fit onto cd or dvd media.
2151 Each archive type is specified by a BackupPC host with its XferMethod
2152 set to 'archive'. This allows for multiple configurations at sites where
2153 there might be a combination of tape and cd/dvd backups being made.
2155 BackupPC provides a menu that allows one or more hosts to be archived.
2156 The most recent backup of each host is archived using BackupPC_tarCreate,
2157 and the output is optionally compressed and split into fixed-sized
2160 The archive for each host is done by default using
2161 __INSTALLDIR__/BackupPC_archiveHost. This script can be copied
2162 and customized as needed.
2164 =head2 Configuring an Archive Host
2166 To create an Archive Host, add it to the hosts file just as any other host
2167 and call it a name that best describes the type of archive, e.g. ArchiveDLT
2169 To tell BackupPC that the Host is for Archives, create a config.pl file in
2170 the Archive Hosts's pc directory, adding the following line:
2172 $Conf{XferMethod} = 'archive';
2174 To further customise the archive's parameters you can adding the changed
2175 parameters in the host's config.pl file. The parameters are explained in
2176 the config.pl file. Parameters may be fixed or the user can be allowed
2177 to change them (eg: output device).
2179 The per-host archive command is $Conf{ArchiveClientCmd}. By default
2180 this invokes __INSTALLDIR__/BackupPC_archiveHost, which you can
2181 copy and customize as necessary.
2183 =head2 Starting an Archive
2185 In the web interface, click on the Archive Host you wish to use. You will see a
2186 list of previous archives and a summary on each. By clicking the "Start Archive"
2187 button you are presented with the list of hosts and the approximate backup size
2188 (note this is raw size, not projected compressed size) Select the hosts you wish
2189 to archive and press the "Archive Selected Hosts" button.
2191 The next screen allows you to adjust the parameters for this archive run.
2192 Press the "Start the Archive" to start archiving the selected hosts with the
2193 parameters displayed.
2195 =head1 BackupPC Design
2197 =head2 Some design issues
2201 =item Pooling common files
2203 To quickly see if a file is already in the pool, an MD5 digest of the
2204 file length and contents is used as the file name in the pool. This
2205 can't guarantee a file is identical: it just reduces the search to
2206 often a single file or handful of files. A complete file comparison
2207 is always done to verify if two files are really the same.
2209 Identical files on multiples backups are represented by hard links.
2210 Hardlinks are used so that identical files all refer to the same
2211 physical file on the server's disk. Also, hard links maintain
2212 reference counts so that BackupPC knows when to delete unused files
2215 For the computer-science majors among you, you can think of the pooling
2216 system used by BackupPC as just a chained hash table stored on a (big)
2219 =item The hashing function
2221 There is a tradeoff between how much of file is used for the MD5 digest
2222 and the time taken comparing all the files that have the same hash.
2224 Using the file length and just the first 4096 bytes of the file for the
2225 MD5 digest produces some repetitions. One example: with 900,000 unique
2226 files in the pool, this hash gives about 7,000 repeated files, and in
2227 the worst case 500 files have the same hash. That's not bad: we only
2228 have to do a single file compare 99.2% of the time. But in the worst
2229 case we have to compare as many as 500 files checking for a match.
2231 With a modest increase in CPU time, if we use the file length and the
2232 first 256K of the file we now only have 500 repeated files and in the
2233 worst case around 20 files have the same hash. Furthermore, if we
2234 instead use the first and last 128K of the file (more specifically, the
2235 first and eighth 128K chunks for files larger than 1MB) we get only 300
2236 repeated files and in the worst case around 20 files have the same hash.
2238 Based on this experimentation, this is the hash function used by BackupPC.
2239 It is important that you don't change the hash function after files
2240 are already in the pool. Otherwise your pool will grow to twice the
2241 size until all the old backups (and all the old files with old hashes)
2246 BackupPC supports compression. It uses the deflate and inflate methods
2247 in the Compress::Zlib module, which is based on the zlib compression
2248 library (see L<http://www.gzip.org/zlib/>).
2250 The $Conf{CompressLevel} setting specifies the compression level to use.
2251 Zero (0) means no compression. Compression levels can be from 1 (least
2252 cpu time, slightly worse compression) to 9 (most cpu time, slightly
2253 better compression). The recommended value is 3. Changing it to 5, for
2254 example, will take maybe 20% more cpu time and will get another 2-3%
2255 additional compression. Diminishing returns set in above 5. See the zlib
2256 documentation for more information about compression levels.
2258 BackupPC implements compression with minimal CPU load. Rather than
2259 compressing every incoming backup file and then trying to match it
2260 against the pool, BackupPC computes the MD5 digest based on the
2261 uncompressed file, and matches against the candidate pool files by
2262 comparing each uncompressed pool file against the incoming backup file.
2263 Since inflating a file takes roughly a factor of 10 less CPU time than
2264 deflating there is a big saving in CPU time.
2266 The combination of pooling common files and compression can yield
2267 a factor of 8 or more overall saving in backup storage.
2271 =head2 BackupPC operation
2273 BackupPC reads the configuration information from
2274 __TOPDIR__/conf/config.pl. It then runs and manages all the backup
2275 activity. It maintains queues of pending backup requests, user backup
2276 requests and administrative commands. Based on the configuration various
2277 requests will be executed simultaneously.
2279 As specified by $Conf{WakeupSchedule}, BackupPC wakes up periodically
2280 to queue backups on all the PCs. This is a four step process:
2286 For each host and DHCP address backup requests are queued on the
2287 background command queue.
2291 For each PC, BackupPC_dump is forked. Several of these may be run in
2292 parallel, based on the configuration. First a ping is done to see if the
2293 machine is alive. If this is a DHCP address, nmblookup is run to get
2294 the netbios name, which is used as the host name. The file
2295 __TOPDIR__/pc/$host/backups is read to decide whether a full or
2296 incremental backup needs to be run. If no backup is scheduled, or the ping
2297 to $host fails, then BackupPC_dump exits.
2299 The backup is done using samba's smbclient or tar over ssh/rsh/nfs piped
2300 into BackupPC_tarExtract, extracting the backup into __TOPDIR__/pc/$host/new.
2301 The smbclient or tar output is put into __TOPDIR__/pc/$host/XferLOG.
2303 As BackupPC_tarExtract extracts the files from smbclient, it checks each
2304 file in the backup to see if it is identical to an existing file from
2305 any previous backup of any PC. It does this without needed to write the
2306 file to disk. If the file matches an existing file, a hardlink is
2307 created to the existing file in the pool. If the file does not match any
2308 existing files, the file is written to disk and the file name is saved
2309 in __TOPDIR__/pc/$host/NewFileList for later processing by
2310 BackupPC_link. BackupPC_tarExtract can handle arbitrarily large
2311 files and multiple candidate matching files without needing to
2312 write the file to disk in the case of a match. This significantly
2313 reduces disk writes (and also reads, since the pool file comparison
2314 is done disk to memory, rather than disk to disk).
2316 Based on the configuration settings, BackupPC_dump checks each
2317 old backup to see if any should be removed. Any expired backups
2318 are moved to __TOPDIR__/trash for later removal by BackupPC_trashClean.
2322 For each complete, good, backup, BackupPC_link is run.
2323 To avoid race conditions as new files are linked into the
2324 pool area, only a single BackupPC_link program runs
2325 at a time and the rest are queued.
2327 BackupPC_link reads the NewFileList written by BackupPC_dump and
2328 inspects each new file in the backup. It re-checks if there is a
2329 matching file in the pool (another BackupPC_link
2330 could have added the file since BackupPC_dump checked). If so, the file
2331 is removed and replaced by a hard link to the existing file. If the file
2332 is new, a hard link to the file is made in the pool area, so that this
2333 file is available for checking against each new file and new backup.
2335 Then, assuming $Conf{IncrFill} is set, for each incremental backup,
2336 hard links are made in the new backup to all files that were not extracted
2337 during the incremental backups. The means the incremental backup looks
2338 like a complete image of the PC (with the exception that files
2339 that were removed on the PC since the last full backup will still
2340 appear in the backup directory tree).
2342 As of v1.03, the CGI interface knows how to merge unfilled
2343 incremental backups will the most recent prior filled (full)
2344 backup, giving the incremental backups a filled appearance. The
2345 default for $Conf{IncrFill} is off, since there is now no need to
2346 fill incremental backups. This saves some level of disk activity,
2347 since lots of extra hardlinks are no longer needed (and don't have
2348 to be deleted when the backup expires).
2352 BackupPC_trashClean is always run in the background to remove any
2353 expired backups. Every 5 minutes it wakes up and removes all the files
2354 in __TOPDIR__/trash.
2356 Also, once each night, BackupPC_nightly is run to complete some additional
2357 administrative tasks, such as cleaning the pool. This involves removing
2358 any files in the pool that only have a single hard link (meaning no backups
2359 are using that file). Again, to avoid race conditions, BackupPC_nightly
2360 is only run when there are no BackupPC_dump or BackupPC_link processes
2365 BackupPC also listens for TCP connections on $Conf{ServerPort}, which
2366 is used by the CGI script BackupPC_Admin for status reporting and
2367 user-initiated backup or backup cancel requests.
2369 =head2 Storage layout
2371 BackupPC resides in three directories:
2375 =item __INSTALLDIR__
2377 Perl scripts comprising BackupPC reside in __INSTALLDIR__/bin,
2378 libraries are in __INSTALLDIR__/lib and documentation
2379 is in __INSTALLDIR__/doc.
2383 The CGI script BackupPC_Admin resides in this cgi binary directory.
2387 All of BackupPC's data (PC backup images, logs, configuration information)
2388 is stored below this directory.
2392 Below __TOPDIR__ are several directories:
2396 =item __TOPDIR__/conf
2398 The directory __TOPDIR__/conf contains:
2404 Configuration file. See L<Configuration file|configuration file>
2405 below for more details.
2409 Hosts file, which lists all the PCs to backup.
2413 =item __TOPDIR__/log
2415 The directory __TOPDIR__/log contains:
2421 Current (today's) log file output from BackupPC.
2423 =item LOG.0 or LOG.0.z
2425 Yesterday's log file output. Log files are aged daily and compressed
2426 (if compression is enabled), and old LOG files are deleted.
2430 Contains BackupPC's process id.
2434 A summary of BackupPC's status written periodically by BackupPC so
2435 that certain state information can be maintained if BackupPC is
2436 restarted. Should not be edited.
2438 =item UserEmailInfo.pl
2440 A summary of what email was last sent to each user, and when the
2441 last email was sent. Should not be edited.
2445 =item __TOPDIR__/trash
2447 Any directories and files below this directory are periodically deleted
2448 whenever BackupPC_trashClean checks. When a backup is aborted or when an
2449 old backup expires, BackupPC_dump simply moves the directory to
2450 __TOPDIR__/trash for later removal by BackupPC_trashClean.
2452 =item __TOPDIR__/pool
2454 All uncompressed files from PC backups are stored below __TOPDIR__/pool.
2455 Each file's name is based on the MD5 hex digest of the file contents.
2456 Specifically, for files less than 256K, the file length and the entire
2457 file is used. For files up to 1MB, the file length and the first and
2458 last 128K are used. Finally, for files longer than 1MB, the file length,
2459 and the first and eighth 128K chunks for the file are used.
2461 Each file is stored in a subdirectory X/Y/Z, where X, Y, Z are the
2462 first 3 hex digits of the MD5 digest.
2464 For example, if a file has an MD5 digest of 123456789abcdef0,
2465 the file is stored in __TOPDIR__/pool/1/2/3/123456789abcdef0.
2467 The MD5 digest might not be unique (especially since not all the file's
2468 contents are used for files bigger than 256K). Different files that have
2469 the same MD5 digest are stored with a trailing suffix "_n" where n is
2470 an incrementing number starting at 0. So, for example, if two additional
2471 files were identical to the first, except the last byte was different,
2472 and assuming the file was larger than 1MB (so the MD5 digests are the
2473 same but the files are actually different), the three files would be
2476 __TOPDIR__/pool/1/2/3/123456789abcdef0
2477 __TOPDIR__/pool/1/2/3/123456789abcdef0_0
2478 __TOPDIR__/pool/1/2/3/123456789abcdef0_1
2480 Both BackupPC_dump (actually, BackupPC_tarExtract) and BackupPC_link are
2481 responsible for checking newly backed up files against the pool. For
2482 each file, the MD5 digest is used to generate a file name in the pool
2483 directory. If the file exists in the pool, the contents are compared.
2484 If there is no match, additional files ending in "_n" are checked.
2485 (Actually, BackupPC_tarExtract compares multiple candidate files in
2486 parallel.) If the file contents exactly match, the file is created by
2487 simply making a hard link to the pool file (this is done by
2488 BackupPC_tarExtract as the backup proceeds). Otherwise,
2489 BackupPC_tarExtract writes the new file to disk and a new hard link is
2490 made in the pool to the file (this is done later by BackupPC_link).
2492 Therefore, every file in the pool will have at least 2 hard links
2493 (one for the pool file and one for the backup file below __TOPDIR__/pc).
2494 Identical files from different backups or PCs will all be linked to
2495 the same file. When old backups are deleted, some files in the pool
2496 might only have one link. BackupPC_nightly checks the entire pool
2497 and removes all files that have only a single link, thereby recovering
2498 the storage for that file.
2500 One other issue: zero length files are not pooled, since there are a lot
2501 of these files and on most file systems it doesn't save any disk space
2502 to turn these files into hard links.
2504 =item __TOPDIR__/cpool
2506 All compressed files from PC backups are stored below __TOPDIR__/cpool.
2507 Its layout is the same as __TOPDIR__/pool, and the hashing function
2508 is the same (and, importantly, based on the uncompressed file, not
2509 the compressed file).
2511 =item __TOPDIR__/pc/$host
2513 For each PC $host, all the backups for that PC are stored below
2514 the directory __TOPDIR__/pc/$host. This directory contains the
2521 Current log file for this PC from BackupPC_dump.
2523 =item LOG.0 or LOG.0.z
2525 Last month's log file. Log files are aged monthly and compressed
2526 (if compression is enabled), and old LOG files are deleted.
2528 =item XferERR or XferERR.z
2530 Output from the transport program (ie: smbclient or tar)
2531 for the most recent failed backup.
2535 Subdirectory in which the current backup is stored. This
2536 directory is renamed if the backup succeeds.
2538 =item XferLOG or XferLOG.z
2540 Output from the transport program (ie: smbclient or tar)
2541 for the current backup.
2543 =item nnn (an integer)
2545 Successful backups are in directories numbered sequentially starting at 0.
2547 =item XferLOG.nnn or XferLOG.nnn.z
2549 Output from the transport program (ie: smbclient or tar)
2550 corresponding to backup number nnn.
2552 =item RestoreInfo.nnn
2554 Information about restore request #nnn including who, what, when, and
2555 why. This file is in Data::Dumper format. (Note that the restore
2556 numbers are not related to the backup number.)
2558 =item RestoreLOG.nnn.z
2560 Output from smbclient or tar during restore #nnn. (Note that the restore
2561 numbers are not related to the backup number.)
2565 Optional configuration settings specific to this host. Settings in this
2566 file override the main configuration file.
2570 A tab-delimited ascii table listing information about each successful
2571 backup, one per row. The columns are:
2577 The backup number, an integer that starts at 0 and increments
2578 for each successive backup. The corresponding backup is stored
2579 in the directory num (eg: if this field is 5, then the backup is
2580 stored in __TOPDIR__/pc/$host/5).
2584 Set to "full" or "incr" for full or incremental backup.
2588 Start time of the backup in unix seconds.
2592 Stop time of the backup in unix seconds.
2596 Number of files backed up (as reported by smbclient or tar).
2600 Total file size backed up (as reported by smbclient or tar).
2604 Number of files that were already in the pool
2605 (as determined by BackupPC_dump and BackupPC_link).
2609 Total size of files that were already in the pool
2610 (as determined by BackupPC_dump and BackupPC_link).
2614 Number of files that were not in the pool
2615 (as determined by BackupPC_link).
2619 Total size of files that were not in the pool
2620 (as determined by BackupPC_link).
2624 Number of errors or warnings from smbclient (zero for tar).
2628 Number of errors from smbclient that were bad file errors (zero for tar).
2632 Number of errors from smbclient that were bad share errors (zero for tar).
2636 Number of errors from BackupPC_tarExtract.
2640 The compression level used on this backup. Zero or empty means no
2645 Total compressed size of files that were already in the pool
2646 (as determined by BackupPC_dump and BackupPC_link).
2650 Total compressed size of files that were not in the pool
2651 (as determined by BackupPC_link).
2655 Set if this backup has not been filled in with the most recent
2656 previous filled or full backup. See $Conf{IncrFill}.
2660 If this backup was filled (ie: noFill is 0) then this is the
2661 number of the backup that it was filled from
2665 Set if this backup has mangled file names and attributes. Always
2666 true for backups in v1.4.0 and above. False for all backups prior
2671 Set to the value of $Conf{XferMethod} when this dump was done.
2675 The level of this dump. A full dump is level 0. Currently incrementals
2676 are 1. But when multi-level incrementals are supported this will reflect
2677 each dump's incremental level.
2683 A tab-delimited ascii table listing information about each requested
2684 restore, one per row. The columns are:
2690 Restore number (matches the suffix of the RestoreInfo.nnn and
2691 RestoreLOG.nnn.z file), unrelated to the backup number.
2695 Start time of the restore in unix seconds.
2699 End time of the restore in unix seconds.
2703 Result (ok or failed).
2707 Error message if restore failed.
2711 Number of files restored.
2715 Size in bytes of the restored files.
2719 Number of errors from BackupPC_tarCreate during restore.
2723 Number of errors from smbclient or tar during restore.
2731 =head2 Compressed file format
2733 The compressed file format is as generated by Compress::Zlib::deflate
2734 with one minor, but important, tweak. Since Compress::Zlib::inflate
2735 fully inflates its argument in memory, it could take large amounts of
2736 memory if it was inflating a highly compressed file. For example, a
2737 200MB file of 0x0 bytes compresses to around 200K bytes. If
2738 Compress::Zlib::inflate was called with this single 200K buffer, it
2739 would need to allocate 200MB of memory to return the result.
2741 BackupPC watches how efficiently a file is compressing. If a big file
2742 has very high compression (meaning it will use too much memory when it
2743 is inflated), BackupPC calls the flush() method, which gracefully
2744 completes the current compression. BackupPC then starts another
2745 deflate and simply appends the output file. So the BackupPC compressed
2746 file format is one or more concatenated deflations/flushes. The specific
2747 ratios that BackupPC uses is that if a 6MB chunk compresses to less
2748 than 64K then a flush will be done.
2750 Back to the example of the 200MB file of 0x0 bytes. Adding flushes
2751 every 6MB adds only 200 or so bytes to the 200K output. So the
2752 storage cost of flushing is negligible.
2754 To easily decompress a BackupPC compressed file, the script
2755 BackupPC_zcat can be found in __INSTALLDIR__/bin. For each
2756 file name argument it inflates the file and writes it to stdout.
2758 =head2 Rsync checksum caching
2760 An incremental backup with rsync compares attributes on the client
2761 with the last full backup. Any files with identical attributes
2762 are skipped. A full backup with rsync sets the --ignore-times
2763 option, which causes every file to be examined independent of
2766 Each file is examined by generating block checksums (default 2K
2767 blocks) on the receiving side (that's the BackupPC side), sending
2768 those checksums to the client, where the remote rsync matches those
2769 checksums with the corresponding file. The matching blocks and new
2770 data is sent back, allowing the client file to be reassembled.
2771 A checksum for the entire file is sent to as an extra check the
2772 the reconstructed file is correct.
2774 This results in significant disk IO and computation for BackupPC:
2775 every file in a full backup, or any file with non-matching attributes
2776 in an incremental backup, needs to be uncompressed, block checksums
2777 computed and sent. Then the receiving side reassembles the file and
2778 has to verify the whole-file checksum. Even if the file is identical,
2779 prior to 2.1.0, BackupPC had to read and uncompress the file twice,
2780 once to compute the block checksums and later to verify the whole-file
2783 Starting in 2.1.0, BackupPC supports optional checksum caching,
2784 which means the block and file checksums only need to be computed
2785 once for each file. This results in a significant performance
2786 improvement. This only works for compressed pool files.
2787 It is enabled by adding
2789 '--checksum-seed=32761',
2791 to $Conf{RsyncArgs} and $Conf{RsyncRestoreArgs}.
2793 Rsync versions prior to and including rsync-2.6.2 need a small patch to
2794 add support for the --checksum-seed option. This patch is available in
2795 the cygwin-rsyncd package at L<http://backuppc.sourceforge.net>.
2796 This patch is already included in rsync CVS, so it will be standard
2797 in future versions of rsync.
2799 When this option is present, BackupPC will add block and file checksums
2800 to the compressed pool file the next time a pool file is used and it
2801 doesn't already have cached checksums. The first time a new file is
2802 written to the pool, the checksums are not appended. The next time
2803 checksums are needed for a file, they are computed and added. So the
2804 full performance benefit of checksum caching won't be noticed until the
2805 third time a pool file is used (eg: the third full backup).
2807 With checksum caching enabled, there is a risk that should a file's contents
2808 in the pool be corrupted due to a disk problem, but the cached checksums
2809 are still correct, the corruption will not be detected by a full backup,
2810 since the file contents are no longer read and compared. To reduce the
2811 chance that this remains undetected, BackupPC can recheck cached checksums
2812 for a fraction of the files. This fraction is set with the
2813 $Conf{RsyncCsumCacheVerifyProb} setting. The default value of 0.01 means
2814 that 1% of the time a file's checksums are read, the checksums are verified.
2815 This reduces performance slightly, but, over time, ensures that files
2816 contents are in sync with the cached checksums.
2818 The format of the cached checksum data can be discovered by looking at
2819 the code. Basically, the first byte of the compressed file is changed
2820 to denote that checksums are appended. The block and file checksum
2821 data, plus some other information and magic word, are appended to the
2822 compressed file. This allows the cache update to be done in-place.
2824 =head2 File name mangling
2826 Backup file names are stored in "mangled" form. Each node of
2827 a path is preceded by "f" (mnemonic: file), and special characters
2828 (\n, \r, % and /) are URI-encoded as "%xx", where xx is the ascii
2829 character's hex value. So c:/craig/example.txt is now stored as
2830 fc/fcraig/fexample.txt.
2832 This was done mainly so meta-data could be stored alongside the backup
2833 files without name collisions. In particular, the attributes for the
2834 files in a directory are stored in a file called "attrib", and mangling
2835 avoids file name collisions (I discarded the idea of having a duplicate
2836 directory tree for every backup just to store the attributes). Other
2837 meta-data (eg: rsync checksums) could be stored in file names preceded
2838 by, eg, "c". There are two other benefits to mangling: the share name
2839 might contain "/" (eg: "/home/craig" for tar transport), and I wanted
2840 that represented as a single level in the storage tree. Secondly, as
2841 files are written to NewFileList for later processing by BackupPC_link,
2842 embedded newlines in the file's path will cause problems which are
2843 avoided by mangling.
2845 The CGI script undoes the mangling, so it is invisible to the user.
2846 Old (unmangled) backups are still supported by the CGI
2849 =head2 Special files
2851 Linux/unix file systems support several special file types: symbolic
2852 links, character and block device files, fifos (pipes) and unix-domain
2853 sockets. All except unix-domain sockets are supported by BackupPC
2854 (there's no point in backing up or restoring unix-domain sockets since
2855 they only have meaning after a process creates them). Symbolic links are
2856 stored as a plain file whose contents are the contents of the link (not
2857 the file it points to). This file is compressed and pooled like any
2858 normal file. Character and block device files are also stored as plain
2859 files, whose contents are two integers separated by a comma; the numbers
2860 are the major and minor device number. These files are compressed and
2861 pooled like any normal file. Fifo files are stored as empty plain files
2862 (which are not pooled since they have zero size). In all cases, the
2863 original file type is stored in the attrib file so it can be correctly
2866 Hardlinks are also supported. When GNU tar first encounters a file with
2867 more than one link (ie: hardlinks) it dumps it as a regular file. When
2868 it sees the second and subsequent hardlinks to the same file, it dumps
2869 just the hardlink information. BackupPC correctly recognizes these
2870 hardlinks and stores them just like symlinks: a regular text file
2871 whose contents is the path of the file linked to. The CGI script
2872 will download the original file when you click on a hardlink.
2874 Also, BackupPC_tarCreate has enough magic to re-create the hardlinks
2875 dynamically based on whether or not the original file and hardlinks
2876 are both included in the tar file. For example, imagine a/b/x is a
2877 hardlink to a/c/y. If you use BackupPC_tarCreate to restore directory
2878 a, then the tar file will include a/b/x as the original file and a/c/y
2879 will be a hardlink to a/b/x. If, instead you restore a/c, then the
2880 tar file will include a/c/y as the original file, not a hardlink.
2882 =head2 Attribute file format
2884 The unix attributes for the contents of a directory (all the files and
2885 directories in that directory) are stored in a file called attrib.
2886 There is a single attrib file for each directory in a backup.
2887 For example, if c:/craig contains a single file c:/craig/example.txt,
2888 that file would be stored as fc/fcraig/fexample.txt and there would be an
2889 attribute file in fc/fcraig/attrib (and also fc/attrib and ./attrib).
2890 The file fc/fcraig/attrib would contain a single entry containing the
2891 attributes for fc/fcraig/fexample.txt.
2893 The attrib file starts with a magic number, followed by the
2894 concatenation of the following information for each file:
2900 File name length in perl's pack "w" format (variable length base 128).
2908 The unix file type, mode, uid, gid and file size divided by 4GB and
2909 file size modulo 4GB (type mode uid gid sizeDiv4GB sizeMod4GB),
2910 in perl's pack "w" format (variable length base 128).
2914 The unix mtime (unix seconds) in perl's pack "N" format (32 bit integer).
2918 The attrib file is also compressed if compression is enabled.
2919 See the lib/BackupPC/Attrib.pm module for full details.
2921 Attribute files are pooled just like normal backup files. This saves
2922 space if all the files in a directory have the same attributes across
2923 multiple backups, which is common.
2925 =head2 Optimizations
2927 BackupPC doesn't care about the access time of files in the pool
2928 since it saves attribute meta-data separate from the files. Since
2929 BackupPC mostly does reads from disk, maintaining the access time of
2930 files generates a lot of unnecessary disk writes. So, provided
2931 BackupPC has a dedicated data disk, you should consider mounting
2932 BackupPC's data directory with the noatime attribute (see mount(1)).
2936 BackupPC isn't perfect (but it is getting better). Here are some
2937 limitations of BackupPC:
2941 =item Non-unix file attributes not backed up
2943 smbclient doesn't extract the WinXX ACLs, so file attributes other than
2944 the equivalent (as provided by smbclient) unix attributes are not
2947 =item Locked files are not backed up
2949 Under WinXX a locked file cannot be read by smbclient. Such files will
2950 not be backed up. This includes the WinXX system registry files.
2952 This is especially troublesome for Outlook, which stores all its data
2953 in a single large file and keeps it locked whenever it is running.
2954 Since many users keep Outlook running all the time their machine
2955 is up their Outlook file will not be backed up. Sadly, this file
2956 is the most important file to backup. As one workaround, Microsoft has
2957 a user-level application that periodically asks the user if they want to
2958 make a copy of their outlook.pst file. This copy can then be backed up
2959 by BackupPC. See L<http://office.microsoft.com/downloads/2002/pfbackup.aspx>.
2961 Similarly, all of the data for WinXX services like SQL databases,
2962 Exchange etc won't be backed up. If these applications support
2963 some kind of export or utility to save their data to disk then this
2964 can =used to create files that BackupPC can backup.
2966 So far, the best that BackupPC can do is send warning emails to
2967 the user saying that their outlook files haven't been backed up in
2968 X days. (X is configurable.) The message invites the user to
2969 exit Outlook and gives a URL to manually start a backup.
2971 I suspect there is a way of mirroring the outlook.pst file so
2972 that at least the mirror copy can be backed up. Or perhaps a
2973 manual copy can be started at login. Does some WinXX expert
2974 know how to do this?
2976 Comment: two users have noted that there are commercial OFM (open file
2977 manager) products that are designed to solve this problem, for example
2978 from St. Bernard or Columbia Data Products. Apparently Veritas and
2979 Legato bundle this product with their commercial products. See for
2980 example L<http://www.stbernard.com/products/docs/ofm_whitepaperV8.pdf>.
2981 If anyone tries these programs with BackupPC please tell us whether or
2984 =item Don't expect to reconstruct a complete WinXX drive
2986 The conclusion from the last few items is that BackupPC is not intended
2987 to allow a complete WinXX disk to be re-imaged from the backup. Our
2988 approach to system restore in the event of catastrophic failure is to
2989 re-image a new disk from a generic master, and then use the BackupPC
2990 archive to restore user files.
2992 It is likely that linux/unix backups done using tar (rather than
2993 smb) can be used to reconstruct a complete file system, although
2996 =item Maximum Backup File Sizes
2998 BackupPC can backup and manage very large file sizes, probably as large
2999 as 2^51 bytes (when a double-precision number's mantissa can no longer
3000 represent an integer exactly). In practice, several things outside
3001 BackupPC limit the maximum individual file size. Any one of the
3002 following items will limit the maximum individual file size:
3008 Perl needs to be compiled with uselargefiles defined. Check your
3011 perl -V | egrep largefiles
3013 Without this, the maximum file size will be 2GB.
3017 The BackupPC pool and data directories must be on a file system that
3018 supports large files.
3020 Without this, the maximum file size will be 2GB.
3024 The transport mechanism also limits the maximum individual file size.
3026 GNU tar maximum file size is limited by the tar header format. The tar
3027 header uses 11 octal digits to represent the file size, which is 33 bits
3028 or 8GB. I vaguely recall (but I haven't recently checked) that GNU tar
3029 uses an extra octal digit (replacing a trailing delimiter) if necessary,
3030 allowing 64GB files. So tar transport limits the maximum file size to
3031 8GB or perhaps 64GB. It is possible that files >= 8GB don't work; this
3032 needs to be looked into.
3034 Smbclient is limited to 4GB file sizes. Moreover, a bug in smbclient
3035 (mixing signed and unsigned 32 bit values) causes it to incorrectly
3036 do the tar octal conversion for file sizes from 2GB-4GB. BackupPC_tarExtract
3037 knows about this bug and can recover the correct file size. So smbclient
3038 transport works up to 4GB file sizes.
3040 Rsync running on Cygwin is limited to either 2GB or 4GB file sizes.
3041 More testing needs to be done to verify the file size limit for
3042 rsync on various platforms.
3046 =item Some tape backup systems aren't smart about hard links
3048 If you backup the BackupPC pool to tape you need to make sure that the
3049 tape backup system is smart about hard links. For example, if you
3050 simply try to tar the BackupPC pool to tape you will backup a lot more
3051 data than is necessary.
3053 Using the example at the start of the installation section, 65 hosts are
3054 backed up with each full backup averaging 3.2GB. Storing one full backup
3055 and two incremental backups per laptop is around 240GB of raw data. But
3056 because of the pooling of identical files, only 87GB is used (with
3057 compression the total is lower). If you run du or tar on the data
3058 directory, there will appear to be 240GB of data, plus the size of the
3059 pool (around 87GB), or 327GB total.
3061 If your tape backup system is not smart about hard links an alternative
3062 is to periodically backup just the last successful backup for each host
3063 to tape. Another alternative is to do a low-level dump of the pool
3064 file system (ie: /dev/hda1 or similar) using dump(1).
3066 Supporting more efficient tape backup is an area for further
3069 =item Incremental backups might included deleted files
3071 To make browsing and restoring backups easier, incremental backups
3072 are "filled-in" from the last complete backup when the backup is
3073 browsed or restored.
3075 However, if a file was deleted by a user after the last full backup, that
3076 file will still appear in the "filled-in" incremental backup. This is not
3077 really a specific problem with BackupPC, rather it is a general issue
3078 with the full/incremental backup paradigm. This minor problem could be
3079 solved by having smbclient list all files when it does the incremental
3080 backup. Volunteers anyone?
3084 Comments or suggestions on these issues are welcome.
3086 =head2 Security issues
3088 Please read this section and consider each of the issues carefully.
3092 =item Smb share password
3094 An important security risk is the manner in which the smb share
3095 passwords are stored. They are in plain text. As described in
3096 L<Step 3: Setting up config.pl|step 3: setting up config.pl> there are four
3097 ways to tell BackupPC the smb share password (manually setting an environment
3098 variable, setting the environment variable in /etc/init.d/backuppc,
3099 putting the password in __TOPDIR__/conf/config.pl, or putting the
3100 password in __TOPDIR__/pc/$host/config.pl). In the latter 3 cases the
3101 smb share password appears in plain text in a file.
3103 If you use any of the latter three methods please make sure that the file's
3104 permission is appropriately restricted. If you also use RCS or CVS, double
3105 check the file permissions of the config.pl,v file.
3107 In future versions there will probably be support for encryption of the
3108 smb share password, but a private key will still have to be stored in a
3109 protected place. Comments and suggestions are welcome.
3111 =item BackupPC socket server
3113 In v1.5.0 the primary method for communication between the CGI program
3114 (BackupPC_Admin) and the server (BackupPC) is via a unix-domain socket.
3115 Since this socket has restricted permissions, no local user should be
3116 able to connect to this port. No backup or restore data passes through
3117 this interface, but an attacker can start or stop backups and get status
3120 If the Apache server and BackupPC_Admin run on a different host to
3121 BackupPC then a TCP port must be enabled by setting $Conf{ServerPort}.
3122 Anyone can connect to this port. To avoid possible attacks via the TCP
3123 socket interface, every client message is protected by an MD5 digest.
3124 The MD5 digest includes four items:
3130 a seed that is sent to the client when the connection opens
3134 a sequence number that increments for each message
3138 a shared secret that is stored in $Conf{ServerMesgSecret}
3146 The message is sent in plain text preceded by the MD5 digest. A
3147 snooper can see the plain-text seed sent by BackupPC and plain-text
3148 message from the client, but cannot construct a valid MD5 digest since
3149 the secret in $Conf{ServerMesgSecret} is unknown. A replay attack is
3150 not possible since the seed changes on a per-connection and
3153 So if you do enable the TCP port, please set $Conf{ServerMesgSecret}
3154 to some hard-to-guess string. A denial-of-service attack is possible
3155 with the TCP port enabled. Someone could simply connect many times
3156 to this port, until BackupPC had exhausted all its file descriptors,
3157 and this would cause new backups and the CGI interface to fail. The
3158 most secure solution is to run BackupPC and Apache on the same machine
3159 and disable the TCP port.
3161 By the way, if you have upgraded from a version of BackupPC prior to
3162 v1.5.0 you should set $Conf{ServerPort} to -1 to disable the TCP port.
3164 =item Installation permissions
3166 It is important to check that the BackupPC scripts in __INSTALLDIR__/bin
3167 and __INSTALLDIR__/lib cannot be edited by normal users. Check the
3168 directory permissions too.
3170 =item Pool permissions
3172 It is important to check that the data files in __TOPDIR__/pool,
3173 __TOPDIR__/pc and __TOPDIR__/trash cannot be read by normal users.
3174 Normal users should not be able to see anything below __TOPDIR__.
3178 Enabling shares on hosts carries security risks. If you are on a private
3179 network and you generally trust your users then there should not be a
3180 problem. But if you have a laptop that is sometimes on public networks
3181 (eg: broadband or even dialup) you should be concerned. A conservative
3182 approach is to use firewall software, and only enable the netbios and
3183 smb ports (137 and 139) on connections from the host running BackupPC.
3185 =item SSH key security
3187 Using ssh for linux/unix clients is quite secure, but the security is
3188 only as good as the protection of ssh's private keys. If an attacker can
3189 devise a way to run a shell as the BackupPC user then they will have
3190 access to BackupPC's private ssh keys. They can then, in turn, ssh to
3191 any client machine as root (or whichever user you have configured
3192 BackupPC to use). This represents a serious compromise of your entire
3193 network. So in vulnerable networks, think carefully about how to protect
3194 the machine running BackupPC and how to prevent attackers from gaining
3195 shell access (as the BackupPC user) to the machine.
3199 The CGI interface, __CGIDIR__/BackupPC_Admin, needs access to the pool
3200 files so it is installed setuid to __BACKUPPCUSER__. The permissions of
3201 this file need to checked carefully. It should be owned by
3202 __BACKUPPCUSER__ and have user and group (but not other) execute
3203 permission. To allow apache/httpd to execute it, the group ownership
3204 should be something that apache/httpd belongs to.
3206 The Apache configuration should be setup for AuthConfig style,
3207 using a .htaccess file so that the user's name is passed into
3208 the script as $ENV{REMOTE_USER}.
3210 If normal users could directly run BackupPC_Admin then there is a serious
3211 security hole: since it is setuid to __BACKUPPCUSER__ any user can
3212 browse and restore any backups. Be aware that anyone who is allowed to
3213 edit or create cgi scripts on your server can execute BackupPC_Admin as
3214 any user! They simply write a cgi script that sets $ENV{REMOTE_USER} and
3215 then execs BackupPC_Admin. The exec succeeds since httpd runs the first
3216 script as user httpd/apache, which in turn has group permission to
3217 execute BackupPC_Admin.
3219 While this setup should be safe, a more conservative approach is to
3220 run a dedicated Apache as user __BACKUPPCUSER__ on a different port.
3221 Then BackupPC_Admin no longer needs to be setuid, and the cgi
3222 directories can be locked down from normal users. Moreover, this
3223 setup is exactly the one used to support mod_perl, so this provides
3224 both the highest performance and the lowest security risk.
3228 Comments and suggestions are welcome.
3230 =head1 Configuration File
3232 The BackupPC configuration file resides in __TOPDIR__/conf/config.pl.
3233 Optional per-PC configuration files reside in __TOPDIR__/pc/$host/config.pl.
3234 This file can be used to override settings just for a particular PC.
3236 =head2 Modifying the main configuration file
3238 The configuration file is a perl script that is executed by BackupPC, so
3239 you should be careful to preserve the file syntax (punctuation, quotes
3240 etc) when you edit it. It is recommended that you use CVS, RCS or some
3241 other method of source control for changing config.pl.
3243 BackupPC reads or re-reads the main configuration file and
3244 the hosts file in three cases:
3254 When BackupPC is sent a HUP (-1) signal. Assuming you installed the
3255 init.d script, you can also do this with "/etc/init.d/backuppc reload".
3259 When the modification time of config.pl file changes. BackupPC
3260 checks the modification time once during each regular wakeup.
3264 Whenever you change the configuration file you can either do
3265 a kill -HUP BackupPC_pid or simply wait until the next regular
3268 Each time the configuration file is re-read a message is reported in the
3269 LOG file, so you can tail it (or view it via the CGI interface) to make
3270 sure your kill -HUP worked. Errors in parsing the configuration file are
3271 also reported in the LOG file.
3273 The optional per-PC configuration file (__TOPDIR__/pc/$host/config.pl)
3274 is read whenever it is needed by BackupPC_dump, BackupPC_link and others.
3276 =head2 Configuration file includes
3278 If you have a heterogeneous set of clients (eg: a variety of WinXX and
3279 linux/unix machines) you will need to create host-specific config.pl files
3280 for some or all of these machines to customize the default settings from
3281 the master config.pl file (at a minimum to set $Conf{XferMethod}).
3283 Since the config.pl file is just regular perl code, you can include
3284 one config file from another. For example, imagine you had three general
3285 classes of machines: WinXX desktops, linux machines in the DMZ and
3286 linux desktops. You could create three config files in __TOPDIR__/conf:
3288 __TOPDIR__/conf/ConfigWinDesktop.pl
3289 __TOPDIR__/conf/ConfigLinuxDMZ.pl
3290 __TOPDIR__/conf/ConfigLinuxDesktop.pl
3292 From each client's directory you can either add a symbolic link to
3293 the appropriate config file:
3295 cd __TOPDIR__/pc/$host
3296 ln -s ../../conf/ConfigWinDesktop.pl config.pl
3298 or, better yet, create a config.pl file in __TOPDIR__/pc/$host
3299 that includes the default config.pl file using perl's "do"
3302 do "__TOPDIR__/conf/ConfigWinDesktop.pl";
3304 This alternative allows you to set other configuration options
3305 specific to each host after the "do" command (perhaps even
3306 overriding the settings in the included file).
3308 Note that you could also include snippets of configuration settings
3309 from the main configuration file. However, be aware that the
3310 modification-time checking that BackupPC does only applies to the
3311 main configuration file: if you change one of the included files,
3312 BackupPC won't notice. You will need to either touch the main
3313 configuration file too, or send BackupPC a HUP (-1) signal.
3315 =head1 Configuration Parameters
3317 The configuration parameters are divided into five general groups.
3318 The first group (general server configuration) provides general
3319 configuration for BackupPC. The next two groups describe what to
3320 backup, when to do it, and how long to keep it. The fourth group
3321 are settings for email reminders, and the final group contains
3322 settings for the CGI interface.
3324 All configuration settings in the second through fifth groups can
3325 be overridden by the per-PC config.pl file.
3329 =head1 Version Numbers
3331 Starting with v1.4.0 BackupPC switched to a X.Y.Z version numbering
3332 system, instead of X.0Y. The first digit is for major new releases, the
3333 middle digit is for significant feature releases and improvements (most
3334 of the releases have been in this category), and the last digit is for
3335 bug fixes. You should think of the old 1.00, 1.01, 1.02 and 1.03 as
3336 1.0.0, 1.1.0, 1.2.0 and 1.3.0.
3340 Craig Barratt <cbarratt@users.sourceforge.net>
3342 See L<http://backuppc.sourceforge.net>.
3346 Copyright (C) 2001-2004 Craig Barratt
3350 Xavier Nicollet, with additions from Guillaume Filion, added the
3351 internationalization (i18n) support to the CGI interface for v2.0.0.
3352 Xavier provided the French translation fr.pm, with additions from
3355 Ryan Kucera contributed the directory navigation code and images
3356 for v1.5.0. He contributed the first skeleton of BackupPC_restore.
3357 He also added a significant revision to the CGI interface, including
3358 CSS tags, in v2.1.0.
3360 Guillaume Filion wrote BackupPC_zipCreate and added the CGI support
3361 for zip download, in addition to some CGI cleanup, for v1.5.0.
3362 Guillaume continues to support fr.pm updates for each
3365 Josh Marshall implemented the Archive feature in v2.1.0.
3367 Javier Gonzalez provided the Spanish translation, es.pm for v2.0.0.
3369 Manfred Herrmann provided the German translation, de.pm for v2.0.0.
3370 Manfred continues to support de.pm updates for each new version.
3372 Lorenzo Cappelletti provided the Italian translation, it.pm for v2.1.0.
3374 Lieven Bridts provided the Dutch translation, nl.pm, for v2.1.0.
3376 Many people have reported bugs, made useful suggestions and helped
3377 with testing; see the ChangeLog and the mail lists.
3379 Your name could appear here in the next version!
3383 This program is free software; you can redistribute it and/or modify it
3384 under the terms of the GNU General Public License as published by the
3385 Free Software Foundation; either version 2 of the License, or (at your
3386 option) any later version.
3388 This program is distributed in the hope that it will be useful,
3389 but WITHOUT ANY WARRANTY; without even the implied warranty of
3390 MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
3391 General Public License for more details.
3393 You should have received a copy of the GNU General Public License in the
3394 LICENSE file along with this program; if not, write to the Free Software
3395 Foundation, Inc., 59 Temple Place, Suite 330, Boston, MA 02111-1307 USA.