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 Unix, Linux and WinXX PCs, desktops and laptops to a server's disk.
10 BackupPC 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
14 a 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, Italian
49 No client-side software is needed. On WinXX the standard smb
50 protocol is used to extract backup data. On linux or unix clients,
51 rsync or tar (over ssh/rsh/nfs) is used to extract backup data.
52 Alternatively, rsync can also be used on WinXX (using cygwin),
53 and Samba could be installed on the linux or unix client to
58 Flexible restore options. Single files can be downloaded from
59 any backup directly from the CGI interface. Zip or Tar archives
60 for selected files or directories from any backup can also be
61 downloaded from the CGI interface. Finally, direct restore to
62 the client machine (using smb or tar) for selected files or
63 directories is also supported from the CGI interface.
67 BackupPC supports mobile environments where laptops are only
68 intermittently connected to the network and have dynamic IP addresses
69 (DHCP). Configuration settings allow machines connected via slower WAN
70 connections (eg: dial up, DSL, cable) to not be backed up, even if they
71 use the same fixed or dynamic IP address as when they are connected
76 Flexible configuration parameters allow multiple backups to be performed
77 in parallel, specification of which shares to backup, which directories
78 to backup or not backup, various schedules for full and incremental
79 backups, schedules for email reminders to users and so on. Configuration
80 parameters can be set system-wide or also on a per-PC basis.
84 Users are sent periodic email reminders if their PC has not
85 recently been backed up. Email content, timing and policies
90 BackupPC is Open Source software hosted by SourceForge.
100 A full backup is a complete backup of a share. BackupPC can be
101 configured to do a full backup at a regular interval (typically
102 weekly). BackupPC can be configured to keep a certain number
103 of full backups. Exponential expiry is also supported, allowing
104 full backups with various vintages to be kept (for example, a
105 settable number of most recent weekly fulls, plus a settable
106 number of older fulls that are 2, 4, 8, or 16 weeks apart).
108 =item Incremental Backup
110 An incremental backup is a backup of files that have changed (based on
111 their modification time) since the last successful full backup. For
112 SMB and tar, BackupPC backups all files that have changed since one
113 hour prior to the start of the last successful full backup. Rsync is
114 more clever: any files whose attributes have changed (ie: uid, gid,
115 mtime, modes, size) since the last full are backed up. Deleted, new
116 files and renamed files are detected by Rsync incrementals.
117 In constrast, SMB and tar incrementals are not able to detect deleted
118 files, renamed files or new files whose modification time is prior to
121 BackupPC can also be configured to keep a certain number of incremental
122 backups, and to keep a smaller number of very old incremental backups.
123 (BackupPC does not support multi-level incremental backups, although it
124 will in a future version.)
126 BackupPC's CGI interface "fills-in" incremental backups based on the
127 last full backup, giving every backup a "full" appearance. This makes
128 browsing and restoring backups easier.
132 When a full backup fails or is canceled, and some files have already
133 been backed up, BackupPC keeps a partial backup containing just the
134 files that were backed up successfully. The partial backup is removed
135 when the next successful backup completes, or if another full backup
136 fails resulting in a newer partial backup. A failed full backup
137 that has not backed up any files, or any failed incremental backup,
138 is removed; no partial backup is saved in these cases.
140 The partial backup may be browsed or used to restore files just like
141 a successful full or incremental backup.
143 With the rsync transfer method the partial backup is used to resume
144 the next full backup, avoiding the need to retransfer the file data
145 already in the partial backup.
147 =item Identical Files
149 BackupPC pools identical files using hardlinks. By "identical
150 files" we mean files with identical contents, not necessary the
151 same permissions, ownership or modification time. Two files might
152 have different permissions, ownership, or modification time but
153 will still be pooled whenever the contents are identical. This
154 is possible since BackupPC stores the file meta-data (permissions,
155 ownership, and modification time) separately from the file contents.
159 Based on your site's requirements you need to decide what your backup
160 policy is. BackupPC is not designed to provide exact re-imaging of
161 failed disks. See L<Limitations|limitations> for more information.
162 However, the addition of tar transport for linux/unix clients, plus
163 full support for special file types and unix attributes in v1.4.0
164 likely means an exact image of a linux/unix file system can be made.
166 BackupPC saves backups onto disk. Because of pooling you can relatively
167 economically keep several weeks of old backups.
169 At some sites the disk-based backup will be adequate, without a
170 secondary tape backup. This system is robust to any single failure: if a
171 client disk fails or loses files, the BackupPC server can be used to
172 restore files. If the server disk fails, BackupPC can be restarted on a
173 fresh file system, and create new backups from the clients. The chance
174 of the server disk failing can be made very small by spending more money
175 on increasingly better RAID systems. However, there is still the risk
176 of catastrophic events like fires or earthquakes that can destroy
177 both the BackupPC server and the clients it is backing up if they
178 are physically nearby.
180 Some sites might choose to do periodic backups to tape or cd/dvd.
181 This backup can be done perhaps weekly using the archive function of
184 Other users have reported success with removable disks to rotate the
185 BackupPC data drives, or using rsync to mirror the BackupPC data pool
194 =item BackupPC home page
196 The BackupPC Open Source project is hosted on SourceForge. The
197 home page can be found at:
199 http://backuppc.sourceforge.net
201 This page has links to the current documentation, the SourceForge
202 project page and general information.
204 =item SourceForge project
206 The SourceForge project page is at:
208 http://sourceforge.net/projects/backuppc
210 This page has links to the current releases of BackupPC.
214 BackupPC has a FAQ at L<http://backuppc.sourceforge.net/faq>.
218 Three BackupPC mailing lists exist for announcements (backuppc-announce),
219 developers (backuppc-devel), and a general user list for support, asking
220 questions or any other topic relevant to BackupPC (backuppc-users).
222 The lists are archived on SourceForge and Gmane. The SourceForge lists
223 are not always up to date and the searching is limited, so Gmane is
224 a good alternative. See:
226 http://news.gmane.org/index.php?prefix=gmane.comp.sysutils.backup.backuppc
227 http://sourceforge.net/mailarchive/forum.php?forum_id=503
229 You can subscribe to these lists by visiting:
231 http://lists.sourceforge.net/lists/listinfo/backuppc-announce
232 http://lists.sourceforge.net/lists/listinfo/backuppc-users
233 http://lists.sourceforge.net/lists/listinfo/backuppc-devel
235 The backuppc-announce list is moderated and is used only for
236 important announcements (eg: new versions). It is low traffic.
237 You only need to subscribe to one of backuppc-announce and
238 backuppc-users: backuppc-users also receives any messages on
241 The backuppc-devel list is only for developers who are working on BackupPC.
242 Do not post questions or support requests there. But detailed technical
243 discussions should happen on this list.
245 To post a message to the backuppc-users list, send an email to
247 backuppc-users@lists.sourceforge.net
249 Do not send subscription requests to this address!
251 =item Other Programs of Interest
253 If you want to mirror linux or unix files or directories to a remote server
254 you should use rsync, L<http://rsync.samba.org>. BackupPC now uses
255 rsync as a transport mechanism; if you are already an rsync user you
256 can think of BackupPC as adding efficient storage (compression and
257 pooling) and a convenient user interface to rsync.
259 Unison is a utility that can do two-way, interactive, synchronization.
260 See L<http://freshmeat.net/projects/unison>. An external wrapper around
261 rsync that maintains transfer data to enable two-way synchronization is
262 drsync; see L<http://freshmeat.net/projects/drsync>.
264 Two popular open source packages that do tape backup are
265 Amanda (L<http://www.amanda.org>)
266 and Bacula (L<http://www.bacula.org>).
267 Amanda can also backup WinXX machines to tape using samba.
268 These packages can be used as back ends to BackupPC to backup the
269 BackupPC server data to tape.
271 Various programs and scripts use rsync to provide hardlinked backups.
272 See, for example, Mike Rubel's site (L<http://www.mikerubel.org/computers/rsync_snapshots>),
273 JW Schultz's dirvish (L<http://www.dirvish.org/>),
274 Ben Escoto's rdiff-backup (L<http://rdiff-backup.stanford.edu>),
275 and John Bowman's rlbackup (L<http://www.math.ualberta.ca/imaging/rlbackup>).
277 BackupPC provides many additional features, such as compressed storage,
278 hardlinking any matching files (rather than just files with the same name),
279 and storing special files without root privileges. But these other scripts
280 provide simple and effective solutions and are definitely worthy of
287 The new features planned for future releases of BackupPC
288 are at L<http://backuppc.sourceforge.net/faq/roadMap.html>.
290 Comments and suggestions are welcome.
294 BackupPC is free. I work on BackupPC because I enjoy doing it and I like
295 to contribute to the open source community.
297 BackupPC already has more than enough features for my own needs. The
298 main compensation for continuing to work on BackupPC is knowing that
299 more and more people find it useful. So feedback is certainly
300 appreciated, both positive and negative.
302 Beyond being a satisfied user and telling other people about it, everyone
303 is encouraged to add links to L<http://backuppc.sourceforge.net>
304 (I'll see them via Google) or otherwise publicize BackupPC. Unlike
305 the commercial products in this space, I have a zero budget (in both
306 time and money) for marketing, PR and advertising, so it's up to
307 all of you! Feel free to vote for BackupPC at
308 L<http://freshmeat.net/projects/backuppc>.
310 Also, everyone is encouraged to contribute patches, bug reports, feature
311 and design suggestions, new code, FAQs, and documentation corrections or
312 improvements. Answering questions on the mail list is a big help too.
314 =head1 Installing BackupPC
324 A linux, solaris, or unix based server with a substantial amount of free
325 disk space (see the next section for what that means). The CPU and disk
326 performance on this server will determine how many simultaneous backups
327 you can run. You should be able to run 4-8 simultaneous backups on a
328 moderately configured server.
330 Several users have reported significantly better performance using
331 reiser compared to ext3 for the BackupPC data file system. It is
332 also recommended you consider either an LVM or raid setup (either
333 in HW or SW; eg: 3Ware RAID5) so that you can expand the
334 file system as necessary.
336 When BackupPC starts with an empty pool, all the backup data will be
337 written to the pool on disk. After more backups are done, a higher
338 percentage of incoming files will already be in the pool. BackupPC is
339 able to avoid writing to disk new files that are already in the pool.
340 So over time disk writes will reduce significantly (by perhaps a factor
341 of 20 or more), since eventually 95% or more of incoming backup files
342 are typically in the pool. Disk reads from the pool are still needed to
343 do file compares to verify files are an exact match. So, with a mature
344 pool, if a relatively fast client generates data at say 1MB/sec, and you
345 run 4 simultaneous backups, there will be an average server disk load of
346 about 4MB/sec reads and 0.2MB/sec writes (assuming 95% of the incoming
347 files are in the pool). These rates will be perhaps 40% lower if
352 Perl version 5.6.0 or later. BackupPC has been tested with
353 version 5.6.x, and 5.8.x. If you don't have perl, please
354 see L<http://www.cpan.org>.
358 Perl modules Compress::Zlib, Archive::Zip and File::RsyncP. Try "perldoc
359 Compress::Zlib" and "perldoc Archive::Zip" to see if you have these
360 modules. If not, fetch them from L<http://www.cpan.org> and see the
361 instructions below for how to build and install them.
363 The File::RsyncP module is available from L<http://perlrsync.sourceforge.net>
364 or CPAN. You'll need to install the File::RsyncP module if you want to use
365 Rsync as a transport method.
369 If you are using smb to backup WinXX machines you need smbclient and
370 nmblookup from the samba package. You will also need nmblookup if
371 you are backing up linux/unix DHCP machines. See L<http://www.samba.org>.
372 Version 2.2.0 or later of Samba is required.
373 Samba versions 3.x are stable and now recommended instead of 2.x.
375 See L<http://www.samba.org> for source and binaries. It's pretty easy to
376 fetch and compile samba, and just grab smbclient and nmblookup, without
377 doing the installation. Alternatively, L<http://www.samba.org> has binary
378 distributions for most platforms.
382 If you are using tar to backup linux/unix machines you should have version
383 1.13.7 at a minimum, with version 1.13.20 or higher recommended. Use
384 "tar --version" to check your version. Various GNU mirrors have the newest
385 versions of tar, see for example L<http://www.funet.fi/pub/gnu/alpha/gnu/tar>.
386 As of June 2003 the latest version is 1.13.25.
390 If you are using rsync to backup linux/unix machines you should have
391 version 2.5.5 or higher on each client machine. See
392 L<http://rsync.samba.org>. Use "rsync --version" to check your version.
394 For BackupPC to use Rsync you will also need to install the perl
395 File::RsyncP module, which is available from
396 L<http://perlrsync.sourceforge.net>.
397 Version 0.52 or later is required.
401 The Apache web server, see L<http://www.apache.org>, preferably built
402 with mod_perl support.
406 =head2 How much disk space do I need?
408 Here's one real example for an environment that is backing up 65 laptops
409 with compression off. Each full backup averages 3.2GB. Each incremental
410 backup averages about 0.2GB. Storing one full backup and two incremental
411 backups per laptop is around 240GB of raw data. But because of the
412 pooling of identical files, only 87GB is used. This is without
415 Another example, with compression on: backing up 95 laptops, where
416 each backup averages 3.6GB and each incremental averages about 0.3GB.
417 Keeping three weekly full backups, and six incrementals is around
418 1200GB of raw data. Because of pooling and compression, only 150GB
421 Here's a rule of thumb. Add up the disk usage of all the machines you
422 want to backup (210GB in the first example above). This is a rough
423 minimum space estimate that should allow a couple of full backups and at
424 least half a dozen incremental backups per machine. If compression is on
425 you can reduce the storage requirements by maybe 30-40%. Add some margin
426 in case you add more machines or decide to keep more old backups.
428 Your actual mileage will depend upon the types of clients, operating
429 systems and applications you have. The more uniform the clients and
430 applications the bigger the benefit from pooling common files.
432 For example, the Eudora email tool stores each mail folder in a separate
433 file, and attachments are extracted as separate files. So in the sadly
434 common case of a large attachment emailed to many recipients, Eudora
435 will extract the attachment into a new file. When these machines are
436 backed up, only one copy of the file will be stored on the server, even
437 though the file appears in many different full or incremental backups. In
438 this sense Eudora is a "friendly" application from the point of view of
439 backup storage requirements.
441 An example at the other end of the spectrum is Outlook. Everything
442 (email bodies, attachments, calendar, contact lists) is stored in a
443 single file, which often becomes huge. Any change to this file requires
444 a separate copy of the file to be saved during backup. Outlook is even
445 more troublesome, since it keeps this file locked all the time, so it
446 cannot be read by smbclient whenever Outlook is running. See the
447 L<Limitations|limitations> section for more discussion of this problem.
449 In addition to total disk space, you shold make sure you have
450 plenty of inodes on your BackupPC data partition. Some users have
451 reported running out of inodes on their BackupPC data partition.
452 So even if you have plenty of disk space, BackupPC will report
453 failures when the inodes are exhausted. This is a particular
454 problem with ext2/ext3 file systems that have a fixed number of
455 inodes when the file system is built. Use "df -i" to see your
458 =head2 Step 1: Getting BackupPC
460 Some linux distributions now include BackupPC. The Debian
461 distribution, supprted by Ludovic Drolez, can be found at
462 L<http://packages.debian.org/backuppc>; it should be included
463 in the next stable Debian release. On Debian, BackupPC can
464 be installed with the command:
466 apt-get install backuppc
468 In the future there might be packages for Gentoo and other
469 linux flavors. If the packaged version is older than the
470 released version then you will probably want to install the
471 lastest version as described below.
473 Otherwise, manually fetching and installing BackupPC is easy.
474 Start by downloading the latest version from
475 L<http://backuppc.sourceforge.net>. Hit the "Code" button,
476 then select the "backuppc" or "backuppc-beta" package and
477 download the latest version.
479 =head2 Step 2: Installing the distribution
481 First off, there are three perl modules you should install.
482 These are all optional, but highly recommended:
488 To enable compression, you will need to install Compress::Zlib
489 from L<http://www.cpan.org>.
490 You can run "perldoc Compress::Zlib" to see if this module is installed.
494 To support restore via Zip archives you will need to install
495 Archive::Zip, also from L<http://www.cpan.org>.
496 You can run "perldoc Archive::Zip" to see if this module is installed.
500 To use rsync and rsyncd with BackupPC you will need to install File::RsyncP.
501 You can run "perldoc File::RsyncP" to see if this module is installed.
502 File::RsyncP is available from L<http://perlrsync.sourceforge.net>.
503 Version 0.52 or later is required.
507 To build and install these packages, fetch the tar.gz file and
508 then run these commands:
510 tar zxvf Archive-Zip-1.01.tar.gz
517 The same sequence of commands can be used for each module.
519 Now let's move onto BackupPC itself. After fetching
520 BackupPC-__VERSION__.tar.gz, run these commands as root:
522 tar zxf BackupPC-__VERSION__.tar.gz
523 cd BackupPC-__VERSION__
526 In the future this release might also have patches available on the
527 SourceForge site. These patch files are text files, with a name of
530 BackupPC-__VERSION__plN.diff
532 where N is the patch level, eg: pl5 is patch-level 5. These
533 patch files are cumulative: you only need apply the last patch
534 file, not all the earlier patch files. If a patch file is
535 available, eg: BackupPC-__VERSION__pl5.diff, you should apply
536 the patch after extracting the tar file:
538 # fetch BackupPC-__VERSION__.tar.gz
539 # fetch BackupPC-__VERSION__pl5.diff
540 tar zxf BackupPC-__VERSION__.tar.gz
541 cd BackupPC-__VERSION__
542 patch -p0 < ../BackupPC-__VERSION__pl5.diff
545 A patch file includes comments that describe that bug fixes
546 and changes. Feel free to review it before you apply the patch.
548 The configure.pl script also accepts command-line options if you
549 wish to run it in a non-interactive manner. It has self-contained
550 documentation for all the command-line options, which you can
555 When you run configure.pl you will be prompted for the full paths
556 of various executables, and you will be prompted for the following
563 It is best if BackupPC runs as a special user, eg backuppc, that has
564 limited privileges. It is preferred that backuppc belongs to a system
565 administrator group so that sys admin members can browse backuppc files,
566 edit the configuration files and so on. Although configurable, the
567 default settings leave group read permission on pool files, so make
568 sure the BackupPC user's group is chosen restrictively.
570 On this installation, this is __BACKUPPCUSER__.
572 For security purposes you might choose to configre the BackupPC
573 user with the shell set to /bin/false. Since you might need to
574 run some BackupPC programs as the BackupPC user for testing
575 purposes, you can use the -s option to su to explicitly run
578 su -s /bin/bash __BACKUPPCUSER__
580 Depending upon your configuration you might also need
585 You need to decide where to put the data directory, below which
586 all the BackupPC data is stored. This needs to be a big file system.
588 On this installation, this is __TOPDIR__.
590 =item Install Directory
592 You should decide where the BackupPC scripts, libraries and documentation
593 should be installed, eg: /opt/local/BackupPC.
595 On this installation, this is __INSTALLDIR__.
597 =item CGI bin Directory
599 You should decide where the BackupPC CGI script resides. This will
600 usually below Apache's cgi-bin directory.
602 On this installation, this is __CGIDIR__.
604 =item Apache image directory
606 A directory where BackupPC's images are stored so that Apache can
607 serve them. This should be somewhere under Apache's DocumentRoot
612 =head2 Step 3: Setting up config.pl
614 After running configure.pl, browse through the config file,
615 __TOPDIR__/conf/config.pl, and make sure all the default settings
616 are correct. In particular, you will need to decide whether to use
617 smb, tar or rsync transport (or whether to set it on a per-PC basis)
618 and set the relevant parameters for that transport method.
619 See the section L<Client Setup|step 5: client setup> for more details.
621 =head2 Step 4: Setting up the hosts file
623 The file __TOPDIR__/conf/hosts contains the list of clients to backup.
624 BackupPC reads this file in three cases:
634 When BackupPC is sent a HUP (-1) signal. Assuming you installed the
635 init.d script, you can also do this with "/etc/init.d/backuppc reload".
639 When the modification time of the hosts file changes. BackupPC
640 checks the modification time once during each regular wakeup.
644 Whenever you change the hosts file (to add or remove a host) you can
645 either do a kill -HUP BackupPC_pid or simply wait until the next regular
648 Each line in the hosts file contains three fields, separated
655 This is typically the host name or NetBios name of the client machine
656 and should be in lower case. The host name can contain spaces (escape
657 with a backslash), but it is not recommended.
659 Please read the section L<How BackupPC Finds Hosts|how backuppc finds hosts>.
661 In certain cases you might want several distinct clients to refer
662 to the same physical machine. For example, you might have a database
663 you want to backup, and you want to bracket the backup of the database
664 with shutdown/restart using $Conf{DumpPreUserCmd} and $Conf{DumpPostUserCmd}.
665 But you also want to backup the rest of the machine while the database
666 is still running. In the case you can specify two different clients in
667 the host file, using any mnemonic name (eg: myhost_mysql and myhost), and
668 use $Conf{ClientNameAlias} in myhost_mysql's config.pl to specify the
669 real host name of the machine.
673 Starting with v2.0.0 the way hosts are discovered has changed and now
674 in most cases you should specify 0 for the DHCP flag, even if the host
675 has a dynamically assigned IP address.
676 Please read the section L<How BackupPC Finds Hosts|how backuppc finds hosts>
677 to understand whether you need to set the DHCP flag.
679 You only need to set DHCP to 1 if your client machine doesn't
680 respond to the NetBios multicast request:
684 but does respond to a request directed to its IP address:
688 If you do set DHCP to 1 on any client you will need to specify the range of
689 DHCP addresses to search is specified in $Conf{DHCPAddressRanges}.
691 Note also that the $Conf{ClientNameAlias} feature does not work for
692 clients with DHCP set to 1.
696 This should be the unix login/email name of the user who "owns" or uses
697 this machine. This is the user who will be sent email about this
698 machine, and this user will have permission to stop/start/browse/restore
699 backups for this host. Leave this blank if no specific person should
700 receive email or be allowed to stop/start/browse/restore backups
701 for this host. Administrators will still have full permissions.
705 Additional user names, separate by commas and with no white space,
706 can be specified. These users will also have full permission in
707 the CGI interface to stop/start/browse/restore backups for this host.
708 These users will not be sent email about this host.
712 The first non-comment line of the hosts file is special: it contains
713 the names of the columns and should not be edited.
715 Here's a simple example of a hosts file:
717 host dhcp user moreUsers
718 farside 0 craig jim,dave
721 =head2 Step 5: Client Setup
723 Two methods for getting backup data from a client are supported: smb and
724 tar. Smb or rsync are the preferred methods for WinXX clients and rsync or
725 tar are the preferred methods for linux/unix clients.
727 The transfer method is set using the $Conf{XferMethod} configuration
728 setting. If you have a mixed environment (ie: you will use smb for some
729 clients and tar for others), you will need to pick the most common
730 choice for $Conf{XferMethod} for the main config.pl file, and then
731 override it in the per-PC config file for those hosts that will use
732 the other method. (Or you could run two completely separate instances
733 of BackupPC, with different data directories, one for WinXX and the
734 other for linux/unix, but then common files between the different
735 machine types will duplicated.)
737 Here are some brief client setup notes:
743 The preferred setup for WinXX clients is to set $Conf{XferMethod} to "smb".
744 (Actually, for v2.0.0, rsyncd is the better method for WinXX if you are
745 prepared to run rsync/cygwin on your WinXX client. More information
746 about this will be provided via the FAQ.)
748 If you want to use rsyncd for WinXX clients you can find a pre-packaged
749 zip file on L<http://backuppc.sourceforge.net>. The package is called
750 cygwin-rsync. It contains rsync.exe, template setup files and the
751 minimal set of cygwin libraries for everything to run. The README file
752 contains instructions for running rsync as a service, so it starts
753 automatically everytime you boot your machine.
755 If you build your own rsync, for rsync 2.6.2 it is strongly
756 recommended you apply the patch in the cygwin-rsync package on
757 L<http://backuppc.sourceforge.net>. This patch adds the --checksum-seed
758 option for checksum caching, and also sends all errors to the client,
759 which is important so BackupPC can log all file access errors.
762 Otherwise, to use SMB, you can either create shares for the data you want
763 to backup or your can use the existing C$ share. To create a new
764 share, open "My Computer", right click on the drive (eg: C), and
765 select "Sharing..." (or select "Properties" and select the "Sharing"
766 tab). In this dialog box you can enable sharing, select the share name
769 All Windows NT based OS (NT, 2000, XP Pro), are configured by default
770 to share the entire C drive as C$. This is a special share used for
771 various administration functions, one of which is to grant access to backup
772 operators. All you need to do is create a new domain user, specifically
773 for backup. Then add the new backup user to the built in "Backup
774 Operators" group. You now have backup capability for any directory on
775 any computer in the domain in one easy step. This avoids using
776 administrator accounts and only grants permission to do exactly what you
777 want for the given user, i.e.: backup.
778 Also, for additional security, you may wish to deny the ability for this
779 user to logon to computers in the default domain policy.
781 If this machine uses DHCP you will also need to make sure the
782 NetBios name is set. Go to Control Panel|System|Network Identification
783 (on Win2K) or Control Panel|System|Computer Name (on WinXP).
784 Also, you should go to Control Panel|Network Connections|Local Area
785 Connection|Properties|Internet Protocol (TCP/IP)|Properties|Advanced|WINS
786 and verify that NetBios is not disabled.
788 The relevant configuration settings are $Conf{SmbShareName},
789 $Conf{SmbShareUserName}, $Conf{SmbSharePasswd}, $Conf{SmbClientPath},
790 $Conf{SmbClientFullCmd}, $Conf{SmbClientIncrCmd} and
791 $Conf{SmbClientRestoreCmd}.
793 BackupPC needs to know the smb share user name and password for a
794 client machine that uses smb. The user name is specified in
795 $Conf{SmbShareUserName}. There are four ways to tell BackupPC the
802 As an environment variable BPC_SMB_PASSWD set before BackupPC starts.
803 If you start BackupPC manually the BPC_SMB_PASSWD variable must be set
804 manually first. For backward compatibility for v1.5.0 and prior, the
805 environment variable PASSWD can be used if BPC_SMB_PASSWD is not set.
806 Warning: on some systems it is possible to see environment variables of
811 Alternatively the BPC_SMB_PASSWD setting can be included in
812 /etc/init.d/backuppc, in which case you must make sure this file
813 is not world (other) readable.
817 As a configuration variable $Conf{SmbSharePasswd} in
818 __TOPDIR__/conf/config.pl. If you put the password
819 here you must make sure this file is not world (other) readable.
823 As a configuration variable $Conf{SmbSharePasswd} in the per-PC
824 configuration file, __TOPDIR__/pc/$host/config.pl. You will have to
825 use this option if the smb share password is different for each host.
826 If you put the password here you must make sure this file is not
827 world (other) readable.
831 Placement and protection of the smb share password is a possible
832 security risk, so please double-check the file and directory
833 permissions. In a future version there might be support for
834 encryption of this password, but a private key will still have to
835 be stored in a protected place. Suggestions are welcome.
837 As an alternative to setting $Conf{XferMethod} to "smb" (using
838 smbclient) for WinXX clients, you can use an smb network filesystem (eg:
839 ksmbfs or similar) on your linux/unix server to mount the share,
840 and then set $Conf{XferMethod} to "tar" (use tar on the network
841 mounted file system).
843 Also, to make sure that file names with 8-bit characters are correctly
844 transferred by smbclient you should add this to samba's smb.conf file
848 # Accept the windows charset
849 client code page = 850
850 character set = ISO8859-1
852 For samba 3.x this should instead be:
855 unix charset = ISO8859-1
857 This setting should work for western europe.
858 See L<http://www.oreilly.com/catalog/samba/chapter/book/ch08_03.html>
859 for more information about settings for other languages.
863 The preferred setup for linux/unix clients is to set $Conf{XferMethod}
864 to "rsync", "rsyncd" or "tar".
866 You can use either rsync, smb, or tar for linux/unix machines. Smb requires
867 that the Samba server (smbd) be run to provide the shares. Since the smb
868 protocol can't represent special files like symbolic links and fifos,
869 tar and rsync are the better transport methods for linux/unix machines.
870 (In fact, by default samba makes symbolic links look like the file or
871 directory that they point to, so you could get an infinite loop if a
872 symbolic link points to the current or parent directory. If you really
873 need to use Samba shares for linux/unix backups you should turn off the
874 "follow symlinks" samba config setting. See the smb.conf manual page.)
876 The requirements for each Xfer Method are:
882 You must have GNU tar on the client machine. Use "tar --version"
883 or "gtar --version" to verify. The version should be at least
884 1.13.7, and 1.13.20 or greater is recommended. Tar is run on
885 the client machine via rsh or ssh.
887 The relevant configuration settings are $Conf{TarClientPath},
888 $Conf{TarShareName}, $Conf{TarClientCmd}, $Conf{TarFullArgs},
889 $Conf{TarIncrArgs}, and $Conf{TarClientRestoreCmd}.
893 You should have at least rsync 2.5.5, and the latest version 2.5.6
894 is recommended. Rsync is run on the remote client via rsh or ssh.
896 The relevant configuration settings are $Conf{RsyncClientPath},
897 $Conf{RsyncClientCmd}, $Conf{RsyncClientRestoreCmd}, $Conf{RsyncShareName},
898 $Conf{RsyncArgs}, and $Conf{RsyncRestoreArgs}.
902 You should have at least rsync 2.5.5, and the latest version 2.6.2
903 is recommended. In this case the rsync daemon should be running on
904 the client machine and BackupPC connects directly to it.
906 The relevant configuration settings are $Conf{RsyncdClientPort},
907 $Conf{RsyncdUserName}, $Conf{RsyncdPasswd}, $Conf{RsyncdAuthRequired},
908 $Conf{RsyncShareName}, $Conf{RsyncArgs}, and $Conf{RsyncRestoreArgs}.
909 $Conf{RsyncShareName} is the name of an rsync module (ie: the thing
910 in square brackets in rsyncd's conf file -- see rsyncd.conf), not a
913 Be aware that rsyncd will remove the leading '/' from path names in
914 symbolic links if you specify "use chroot = no" in the rsynd.conf file.
915 See the rsyncd.conf manual page for more information.
919 For linux/unix machines you should not backup "/proc". This directory
920 contains a variety of files that look like regular files but they are
921 special files that don't need to be backed up (eg: /proc/kcore is a
922 regular file that contains physical memory). See $Conf{BackupFilesExclude}.
923 It is safe to back up /dev since it contains mostly character-special
924 and block-special files, which are correctly handed by BackupPC
925 (eg: backing up /dev/hda5 just saves the block-special file information,
926 not the contents of the disk).
928 Alternatively, rather than backup all the file systems as a single
929 share ("/"), it is easier to restore a single file system if you backup
930 each file system separately. To do this you should list each file system
931 mount point in $Conf{TarShareName} or $Conf{RsyncShareName}, and add the
932 --one-file-system option to $Conf{TarClientCmd} or add --one-file-system
933 (note the different punctuation) to $Conf{RsyncArgs}. In this case there
934 is no need to exclude /proc explicitly since it looks like a different
937 Next you should decide whether to run tar over ssh, rsh or nfs. Ssh is
938 the preferred method. Rsh is not secure and therefore not recommended.
939 Nfs will work, but you need to make sure that the BackupPC user (running
940 on the server) has sufficient permissions to read all the files below
943 Ssh allows BackupPC to run as a privileged user on the client (eg:
944 root), since it needs sufficient permissions to read all the backup
945 files. Ssh is setup so that BackupPC on the server (an otherwise low
946 privileged user) can ssh as root on the client, without being prompted
947 for a password. There are two common versions of ssh: v1 and v2. Here
948 are some instructions for one way to setup ssh. (Check which version
949 of SSH you have by typing "ssh" or "man ssh".)
953 In general this should be similar to Linux/Unix machines.
954 Mark Stosberg reports that you can also use hfstar.
955 See L<http://fink.sourceforge.net/pdb/package.php/hfstar>.
959 SSH is a secure way to run tar or rsync on a backup client to extract
960 the data. SSH provides strong authentication and encryption of
963 Note that if you run rsyncd (rsync daemon), ssh is not used.
964 In this case, rsyncd provides its own authentication, but there
965 is no encryption of network data. If you want encryption of
966 network data you can use ssh to create a tunnel, or use a
967 program like stunnel. If someone submits instructions I
969 Setup instructions for ssh are at
970 L<http://backuppc.sourceforge.net/faq/ssh.html>.
972 =item Clients that use DHCP
974 If a client machine uses DHCP BackupPC needs some way to find the
975 IP address given the host name. One alternative is to set dhcp
976 to 1 in the hosts file, and BackupPC will search a pool of IP
977 addresses looking for hosts. More efficiently, it is better to
978 set dhcp = 0 and provide a mechanism for BackupPC to find the
979 IP address given the host name.
981 For WinXX machines BackupPC uses the NetBios name server to determine
982 the IP address given the host name.
983 For unix machines you can run nmbd (the NetBios name server) from
984 the Samba distribution so that the machine responds to a NetBios
985 name request. See the manual page and Samba documentation for more
988 Alternatively, you can set $Conf{NmbLookupFindHostCmd} to any command
989 that returns the IP address given the host name.
991 Please read the section L<How BackupPC Finds Hosts|how backuppc finds hosts>
996 =head2 Step 6: Running BackupPC
998 The installation contains an init.d backuppc script that can be copied
999 to /etc/init.d so that BackupPC can auto-start on boot.
1000 See init.d/README for further instructions.
1002 BackupPC should be ready to start. If you installed the init.d script,
1003 then you should be able to run BackupPC with:
1005 /etc/init.d/backuppc start
1007 (This script can also be invoked with "stop" to stop BackupPC and "reload"
1008 to tell BackupPC to reload config.pl and the hosts file.)
1012 __INSTALLDIR__/bin/BackupPC -d
1014 as user __BACKUPPCUSER__. The -d option tells BackupPC to run as a daemon
1015 (ie: it does an additional fork).
1017 Any immediate errors will be printed to stderr and BackupPC will quit.
1018 Otherwise, look in __TOPDIR__/log/LOG and verify that BackupPC reports
1019 it has started and all is ok.
1021 =head2 Step 7: Talking to BackupPC
1023 You should verify that BackupPC is running by using BackupPC_serverMesg.
1024 This sends a message to BackupPC via the unix (or TCP) socket and prints
1025 the response. Like all BackupPC programs, BackupPC_serverMesg
1026 should be run as the BackupPC user (__BACKUPPCUSER__), so you
1031 before running BackupPC_serverMesg. If the BackupPC user is
1032 configured with /bin/false as the shell, you can use the -s
1033 option to su to explicitly run a shell, eg:
1035 su -s /bin/bash __BACKUPPCUSER__
1037 Depending upon your configuration you might also need
1040 You can request status information and start and stop backups using this
1041 interface. This socket interface is mainly provided for the CGI interface
1042 (and some of the BackupPC sub-programs use it too). But right now we just
1043 want to make sure BackupPC is happy. Each of these commands should
1044 produce some status output:
1046 __INSTALLDIR__/bin/BackupPC_serverMesg status info
1047 __INSTALLDIR__/bin/BackupPC_serverMesg status jobs
1048 __INSTALLDIR__/bin/BackupPC_serverMesg status hosts
1050 The output should be some hashes printed with Data::Dumper. If it
1051 looks cryptic and confusing, and doesn't look like an error message,
1054 The jobs status should initially show just BackupPC_trashClean.
1055 The hosts status should produce a list of every host you have listed
1056 in __TOPDIR__/conf/hosts as part of a big cryptic output line.
1058 You can also request that all hosts be queued:
1060 __INSTALLDIR__/bin/BackupPC_serverMesg backup all
1062 At this point you should make sure the CGI interface works since
1063 it will be much easier to see what is going on. That's our
1066 =head2 Step 8: CGI interface
1068 The CGI interface script, BackupPC_Admin, is a powerful and flexible
1069 way to see and control what BackupPC is doing. It is written for an
1070 Apache server. If you don't have Apache, see L<http://www.apache.org>.
1072 There are two options for setting up the CGI interface: standard
1073 mode and using mod_perl. Mod_perl provides much higher performance
1074 (around 15x) and is the best choice if your Apache was built with
1075 mod_perl support. To see if your apache was built with mod_perl
1078 httpd -l | egrep mod_perl
1080 If this prints mod_perl.c then your Apache supports mod_perl.
1082 Using mod_perl with BackupPC_Admin requires a dedicated Apache
1083 to be run as the BackupPC user (__BACKUPPCUSER__). This is
1084 because BackupPC_Admin needs permission to access various files
1085 in BackupPC's data directories. In contrast, the standard
1086 installation (without mod_perl) solves this problem by having
1087 BackupPC_Admin installed as setuid to the BackupPC user, so that
1088 BackupPC_Admin runs as the BackuPC user.
1090 Here are some specifics for each setup:
1094 =item Standard Setup
1096 The CGI interface should have been installed by the configure.pl script
1097 in __CGIDIR__/BackupPC_Admin. BackupPC_Admin should have been installed
1098 as setuid to the BackupPC user (__BACKUPPCUSER__), in addition to user
1099 and group execute permission.
1101 You should be very careful about permissions on BackupPC_Admin and
1102 the directory __CGIDIR__: it is important that normal users cannot
1103 directly execute or change BackupPC_Admin, otherwise they can access
1104 backup files for any PC. You might need to change the group ownership
1105 of BackupPC_Admin to a group that Apache belongs to so that Apache
1106 can execute it (don't add "other" execute permission!).
1107 The permissions should look like this:
1109 ls -l __CGIDIR__/BackupPC_Admin
1110 -swxr-x--- 1 __BACKUPPCUSER__ web 82406 Jun 17 22:58 __CGIDIR__/BackupPC_Admin
1112 The setuid script won't work unless perl on your machine was installed
1113 with setuid emulation. This is likely the problem if you get an error
1114 saying such as "Wrong user: my userid is 25, instead of 150", meaning
1115 the script is running as the httpd user, not the BackupPC user.
1116 This is because setuid scripts are disabled by the kernel in most
1117 flavors of unix and linux.
1119 To see if your perl has setuid emulation, see if there is a program
1120 called sperl5.6.0 (or sperl5.8.2 etc, based on your perl version)
1121 in the place where perl is installed. If you can't find this program,
1122 then you have two options: rebuild and reinstall perl with the setuid
1123 emulation turned on (answer "y" to the question "Do you want to do
1124 setuid/setgid emulation?" when you run perl's configure script), or
1125 switch to the mod_perl alternative for the CGI script (which doesn't
1126 need setuid to work).
1128 =item Mod_perl Setup
1130 The advantage of the mod_perl setup is that no setuid script is needed,
1131 and there is a huge performance advantage. Not only does all the perl
1132 code need to be parsed just once, the config.pl and hosts files, plus
1133 the connection to the BackupPC server are cached between requests. The
1134 typical speedup is around 15 times.
1136 To use mod_perl you need to run Apache as user __BACKUPPCUSER__.
1137 If you need to run multiple Apache's for different services then
1138 you need to create multiple top-level Apache directories, each
1139 with their own config file. You can make copies of /etc/init.d/httpd
1140 and use the -d option to httpd to point each http to a different
1141 top-level directory. Or you can use the -f option to explicitly
1142 point to the config file. Multiple Apache's will run on different
1143 Ports (eg: 80 is standard, 8080 is a typical alternative port accessed
1144 via http://yourhost.com:8080).
1146 Inside BackupPC's Apache http.conf file you should check the
1147 settings for ServerRoot, DocumentRoot, User, Group, and Port. See
1148 L<http://httpd.apache.org/docs/server-wide.html> for more details.
1150 For mod_perl, BackupPC_Admin should not have setuid permission, so
1151 you should turn it off:
1153 chmod u-s __CGIDIR__/BackupPC_Admin
1155 To tell Apache to use mod_perl to execute BackupPC_Admin, add this
1156 to Apache's 1.x httpd.conf file:
1158 <IfModule mod_perl.c>
1159 PerlModule Apache::Registry
1161 <Location /cgi-bin/BackupPC/BackupPC_Admin> # <--- change path as needed
1162 SetHandler perl-script
1163 PerlHandler Apache::Registry
1169 Apache 2.0.44 with Perl 5.8.0 on RedHat 7.1, Don Silvia reports that
1170 this works (with tweaks from Michael Tuzi):
1172 LoadModule perl_module modules/mod_perl.so
1175 <Directory /path/to/cgi/>
1176 SetHandler perl-script
1177 PerlResponseHandler ModPerl::Registry
1178 PerlOptions +ParseHeaders
1182 Allow from 192.168.0
1183 AuthName "Backup Admin"
1185 AuthUserFile /path/to/user_file
1189 There are other optimizations and options with mod_perl. For
1190 example, you can tell mod_perl to preload various perl modules,
1191 which saves memory compared to loading separate copies in every
1192 Apache process after they are forked. See Stas's definitive
1193 mod_perl guide at L<http://perl.apache.org/guide>.
1197 BackupPC_Admin requires that users are authenticated by Apache.
1198 Specifically, it expects that Apache sets the REMOTE_USER environment
1199 variable when it runs. There are several ways to do this. One way
1200 is to create a .htaccess file in the cgi-bin directory that looks like:
1202 AuthGroupFile /etc/httpd/conf/group # <--- change path as needed
1203 AuthUserFile /etc/http/conf/passwd # <--- change path as needed
1208 You will also need "AllowOverride Indexes AuthConfig" in the Apache
1209 httpd.conf file to enable the .htaccess file. Alternatively, everything
1210 can go in the Apache httpd.conf file inside a Location directive. The
1211 list of users and password file above can be extracted from the NIS
1214 One alternative is to use LDAP. In Apache's http.conf add these lines:
1216 LoadModule auth_ldap_module modules/auth_ldap.so
1217 AddModule auth_ldap.c
1219 # cgi-bin - auth via LDAP (for BackupPC)
1220 <Location /cgi-binBackupPC/BackupPC_Admin> # <--- change path as needed
1222 AuthName "BackupPC login"
1223 # replace MYDOMAIN, PORT, ORG and CO as needed
1224 AuthLDAPURL ldap://ldap.MYDOMAIN.com:PORT/o=ORG,c=CO?uid?sub?(objectClass=*)
1228 If you want to disable the user authentication you can set
1229 $Conf{CgiAdminUsers} to '*', which allows any user to have
1230 full access to all hosts and backups. In this case the REMOTE_USER
1231 environment variable does not have to be set by Apache.
1233 Alternatively, you can force a particular user name by getting Apache
1234 to set REMOTE_USER, eg, to hardcode the user to www you could add
1235 this to Apache's httpd.conf:
1237 <Location /cgi-bin/BackupPC/BackupPC_Admin> # <--- change path as needed
1238 Setenv REMOTE_USER www
1241 Finally, you should also edit the config.pl file and adjust, as necessary,
1242 the CGI-specific settings. They're near the end of the config file. In
1243 particular, you should specify which users or groups have administrator
1244 (privileged) access: see the config settings $Conf{CgiAdminUserGroup}
1245 and $Conf{CgiAdminUsers}. Also, the configure.pl script placed various
1246 images into $Conf{CgiImageDir} that BackupPC_Admin needs to serve
1247 up. You should make sure that $Conf{CgiImageDirURL} is the correct
1248 URL for the image directory.
1250 See the section L<Fixing installation problems|fixing installation problems> for suggestions on debugging the Apache authentication setup.
1252 =head2 How BackupPC Finds Hosts
1254 Starting with v2.0.0 the way hosts are discovered has changed. In most
1255 cases you should specify 0 for the DHCP flag in the conf/hosts file,
1256 even if the host has a dynamically assigned IP address.
1258 BackupPC (starting with v2.0.0) looks up hosts with DHCP = 0 in this manner:
1264 First DNS is used to lookup the IP address given the client's name
1265 using perl's gethostbyname() function. This should succeed for machines
1266 that have fixed IP addresses that are known via DNS. You can manually
1267 see whether a given host have a DNS entry according to perls'
1268 gethostbyname function with this command:
1270 perl -e 'print(gethostbyname("myhost") ? "ok\n" : "not found\n");'
1274 If gethostbyname() fails, BackupPC then attempts a NetBios multicast to
1275 find the host. Provided your client machine is configured properly,
1276 it should respond to this NetBios multicast request. Specifically,
1277 BackupPC runs a command of this form:
1281 If this fails you will see output like:
1283 querying myhost on 10.10.255.255
1284 name_query failed to find name myhost
1286 If this success you will see output like:
1288 querying myhost on 10.10.255.255
1289 10.10.1.73 myhost<00>
1291 Depending on your netmask you might need to specify the -B option to
1292 nmblookup. For example:
1294 nmblookup -B 10.10.1.255 myhost
1296 If necessary, experiment on the nmblookup command that will return the
1297 IP address of the client given its name. Then update
1298 $Conf{NmbLookupFindHostCmd} with any necessary options to nmblookup.
1302 For hosts that have the DHCP flag set to 1, these machines are
1303 discovered as follows:
1309 A DHCP address pool ($Conf{DHCPAddressRanges}) needs to be specified.
1310 BackupPC will check the NetBIOS name of each machine in the range using
1311 a command of the form:
1313 nmblookup -A W.X.Y.Z
1315 where W.X.Y.Z is each candidate address from $Conf{DHCPAddressRanges}.
1316 Any host that has a valid NetBIOS name returned by this command (ie:
1317 matching an entry in the hosts file) will be backed up. You can
1318 modify the specific nmblookup command if necessary via $Conf{NmbLookupCmd}.
1322 You only need to use this DHCP feature if your client machine doesn't
1323 respond to the NetBios multicast request:
1327 but does respond to a request directed to its IP address:
1329 nmblookup -A W.X.Y.Z
1333 =head2 Other installation topics
1337 =item Removing a client
1339 If there is a machine that no longer needs to be backed up (eg: a retired
1340 machine) you have two choices. First, you can keep the backups accessible
1341 and browsable, but disable all new backups. Alternatively, you can
1342 completely remove the client and all its backups.
1344 To disable backups for a client there are two special values for
1345 $Conf{FullPeriod} in that client's per-PC config.pl file:
1351 Don't do any regular backups on this machine. Manually
1352 requested backups (via the CGI interface) will still occur.
1356 Don't do any backups on this machine. Manually requested
1357 backups (via the CGI interface) will be ignored.
1361 This will still allow that client's old backups to be browsable
1364 To completely remove a client and all its backups, you should remove its
1365 entry in the conf/hosts file, and then delete the __TOPDIR__/pc/$host
1366 directory. Whenever you change the hosts file, you should send
1367 BackupPC a HUP (-1) signal so that it re-reads the hosts file.
1368 If you don't do this, BackupPC will automatically re-read the
1369 hosts file at the next regular wakeup.
1371 Note that when you remove a client's backups you won't initially recover
1372 a lot of disk space. That's because the client's files are still in
1373 the pool. Overnight, when BackupPC_nightly next runs, all the unused
1374 pool files will be deleted and this will recover the disk space used
1375 by the client's backups.
1377 =item Copying the pool
1379 If the pool disk requirements grow you might need to copy the entire
1380 data directory to a new (bigger) file system. Hopefully you are lucky
1381 enough to avoid this by having the data directory on a RAID file system
1382 or LVM that allows the capacity to be grown in place by adding disks.
1384 The backup data directories contain large numbers of hardlinks. If
1385 you try to copy the pool the target directory will occupy a lot more
1386 space if the hardlinks aren't re-established.
1388 The GNU cp program with the -a option is aware of hardlinks and knows
1389 to re-establish them. So GNU cp -a is the recommended way to copy
1390 the data directory and pool. Don't forget to stop BackupPC while
1393 =item Compressing an existing pool
1395 If you are upgrading BackupPC and want to turn compression on you have
1402 Simply turn on compression. All new backups will be compressed. Both old
1403 (uncompressed) and new (compressed) backups can be browsed and viewed.
1404 Eventually, the old backups will expire and all the pool data will be
1405 compressed. However, until the old backups expire, this approach could
1406 require 60% or more additional pool storage space to store both
1407 uncompressed and compressed versions of the backup files.
1411 Convert all the uncompressed pool files and backups to compressed.
1412 The script __INSTALLDIR__/bin/BackupPC_compressPool does this.
1413 BackupPC must not be running when you run BackupPC_compressPool.
1414 Also, there must be no existing compressed backups when you
1415 run BackupPC_compressPool.
1417 BackupPC_compressPool compresses all the files in the uncompressed pool
1418 (__TOPDIR__/pool) and moves them to the compressed pool
1419 (__TOPDIR__/cpool). It rewrites the files in place, so that the
1420 existing hardlinks are not disturbed.
1424 The rest of this section discusses how to run BackupPC_compressPool.
1426 BackupPC_compressPool takes three command line options:
1432 Test mode: do everything except actually replace the pool files.
1433 Useful for estimating total run time without making any real
1438 Read check: re-read the compressed file and compare it against
1439 the original uncompressed file. Can only be used in test mode.
1443 Number of children to fork. BackupPC_compressPool can take a long time
1444 to run, so to speed things up it spawns four children, each working on a
1445 different part of the pool. You can change the number of children with
1450 Here are the recommended steps for running BackupPC_compressPool:
1456 Stop BackupPC (eg: "/etc/init.d/backuppc stop").
1460 Set $Conf{CompressLevel} to a non-zero number (eg: 3).
1464 Do a dry run of BackupPC_compressPool. Make sure you run this as
1465 the BackupPC user (__BACKUPPCUSER__):
1467 BackupPC_compressPool -t -r
1469 The -t option (test mode) makes BackupPC_compressPool do all the steps,
1470 but not actually change anything. The -r option re-reads the compressed
1471 file and compares it against the original.
1473 BackupPC_compressPool gives a status as it completes each 1% of the job.
1474 It also shows the cumulative compression ratio and estimated completion
1475 time. Once you are comfortable that things look ok, you can kill
1476 BackupPC_compressPool or wait for it to finish.
1480 Now you are ready to run BackupPC_compressPool for real. Once again,
1481 as the BackupPC user (__BACKUPPCUSER__), run:
1483 BackupPC_compressPool
1485 You should put the output into a file and tail this file. (The running
1486 time could be twice as long as the test mode since the test mode file
1487 writes are immediately followed by an unlink, so in test mode it is
1488 likely the file writes never make it to disk.)
1490 It is B<critical> that BackupPC_compressPool runs to completion before
1491 re-starting BackupPC. Before BackupPC_compressPool completes, none of
1492 the existing backups will be in a consistent state. If you must stop
1493 BackupPC_compressPool for some reason, send it an INT or TERM signal
1494 and give it several seconds (or more) to clean up gracefully.
1495 After that, you can re-run BackupPC_compressPool and it will start
1496 again where it left off. Once again, it is critical that it runs
1501 After BackupPC_compressPool completes you should have a complete set
1502 of compressed backups (and your disk usage should be lower). You
1503 can now re-start BackupPC.
1507 =head2 Fixing installation problems
1509 Please see the FAQ at L<http://backuppc.sourceforge.net/faq> for
1510 debugging suggestions.
1512 =head1 Restore functions
1514 BackupPC supports several different methods for restoring files. The
1515 most convenient restore options are provided via the CGI interface.
1516 Alternatively, backup files can be restored using manual commands.
1518 =head2 CGI restore options
1520 By selecting a host in the CGI interface, a list of all the backups
1521 for that machine will be displayed. By selecting the backup number
1522 you can navigate the shares and directory tree for that backup.
1524 BackupPC's CGI interface automatically fills incremental backups
1525 with the corresponding full backup, which means each backup has
1526 a filled appearance. Therefore, there is no need to do multiple
1527 restores from the incremental and full backups: BackupPC does all
1528 the hard work for you. You simply select the files and directories
1529 you want from the correct backup vintage in one step.
1531 You can download a single backup file at any time simply by selecting
1532 it. Your browser should prompt you with the file name and ask you
1533 whether to open the file or save it to disk.
1535 Alternatively, you can select one or more files or directories in
1536 the currently selected directory and select "Restore selected files".
1537 (If you need to restore selected files and directories from several
1538 different parent directories you will need to do that in multiple
1541 If you select all the files in a directory, BackupPC will replace
1542 the list of files with the parent directory. You will be presented
1543 with a screen that has three options:
1547 =item Option 1: Direct Restore
1549 With this option the selected files and directories are restored
1550 directly back onto the host, by default in their original location.
1551 Any old files with the same name will be overwritten, so use caution.
1552 You can optionally change the target host name, target share name,
1553 and target path prefix for the restore, allowing you to restore the
1554 files to a different location.
1556 Once you select "Start Restore" you will be prompted one last time
1557 with a summary of the exact source and target files and directories
1558 before you commit. When you give the final go ahead the restore
1559 operation will be queued like a normal backup job, meaning that it
1560 will be deferred if there is a backup currently running for that host.
1561 When the restore job is run, smbclient, tar, rsync or rsyncd is used
1562 (depending upon $Conf{XferMethod}) to actually restore the files.
1563 Sorry, there is currently no option to cancel a restore that has been
1566 A record of the restore request, including the result and list of
1567 files and directories, is kept. It can be browsed from the host's
1568 home page. $Conf{RestoreInfoKeepCnt} specifies how many old restore
1569 status files to keep.
1571 Note that for direct restore to work, the $Conf{XferMethod} must
1572 be able to write to the client. For example, that means an SMB
1573 share for smbclient needs to be writable, and the rsyncd module
1574 needs "read only" set to "false". This creates additional security
1575 risks. If you only create read-only SMB shares (which is a good
1576 idea), then the direct restore will fail. You can disable the
1577 direct restore option by setting $Conf{SmbClientRestoreCmd},
1578 $Conf{TarClientRestoreCmd} and $Conf{RsyncRestoreArgs} to undef.
1580 =item Option 2: Download Zip archive
1582 With this option a zip file containing the selected files and directories
1583 is downloaded. The zip file can then be unpacked or individual files
1584 extracted as necessary on the host machine. The compression level can be
1585 specified. A value of 0 turns off compression.
1587 When you select "Download Zip File" you should be prompted where to
1588 save the restore.zip file.
1590 BackupPC does not consider downloading a zip file as an actual
1591 restore operation, so the details are not saved for later browsing
1592 as in the first case. However, a mention that a zip file was
1593 downloaded by a particular user, and a list of the files, does
1594 appear in BackupPC's log file.
1596 =item Option 3: Download Tar archive
1598 This is identical to the previous option, except a tar file is downloaded
1599 rather than a zip file (and there is currently no compression option).
1603 =head2 Command-line restore options
1605 Apart from the CGI interface, BackupPC allows you to restore files
1606 and directories from the command line. The following programs can
1613 For each file name argument it inflates (uncompresses) the file and
1614 writes it to stdout. To use BackupPC_zcat you could give it the
1617 __INSTALLDIR__/bin/BackupPC_zcat __TOPDIR__/pc/host/5/fc/fcraig/fexample.txt > example.txt
1619 It's your responsibility to make sure the file is really compressed:
1620 BackupPC_zcat doesn't check which backup the requested file is from.
1621 BackupPC_zcat returns a non-zero status if it fails to uncompress
1624 =item BackupPC_tarCreate
1626 BackupPC_tarCreate creates a tar file for any files or directories in
1627 a particular backup. Merging of incrementals is done automatically,
1628 so you don't need to worry about whether certain files appear in the
1629 incremental or full backup.
1633 BackupPC_tarCreate [-t] [-h host] [-n dumpNum] [-s shareName]
1634 [-r pathRemove] [-p pathAdd] [-b BLOCKS] [-w writeBufSz]
1635 files/directories...
1637 The command-line files and directories are relative to the specified
1638 shareName. The tar file is written to stdout.
1640 The required options are:
1646 host from which the tar archive is created
1650 dump number from which the tar archive is created
1654 share name from which the tar archive is created
1664 print summary totals
1668 path prefix that will be replaced with pathAdd
1676 the tar block size, default is 20, meaning tar writes data in 20 * 512
1681 write buffer size, default 1048576 (1MB). You can increase this if
1682 you are trying to stream to a fast tape device.
1686 The -h, -n and -s options specify which dump is used to generate
1687 the tar archive. The -r and -p options can be used to relocate
1688 the paths in the tar archive so extracted files can be placed
1689 in a location different from their original location.
1691 =item BackupPC_zipCreate
1693 BackupPC_zipCreate creates a zip file for any files or directories in
1694 a particular backup. Merging of incrementals is done automatically,
1695 so you don't need to worry about whether certain files appear in the
1696 incremental or full backup.
1700 BackupPC_zipCreate [-t] [-h host] [-n dumpNum] [-s shareName]
1701 [-r pathRemove] [-p pathAdd] [-c compressionLevel]
1702 files/directories...
1704 The command-line files and directories are relative to the specified
1705 shareName. The zip file is written to stdout.
1707 The required options are:
1713 host from which the zip archive is created
1717 dump number from which the zip archive is created
1721 share name from which the zip archive is created
1731 print summary totals
1735 path prefix that will be replaced with pathAdd
1743 compression level (default is 0, no compression)
1747 The -h, -n and -s options specify which dump is used to generate
1748 the zip archive. The -r and -p options can be used to relocate
1749 the paths in the zip archive so extracted files can be placed
1750 in a location different from their original location.
1754 Each of these programs reside in __INSTALLDIR__/bin.
1756 =head1 Archive functions
1758 BackupPC supports archiving to removable media. For users that require
1759 offsite backups, BackupPC can create archives that stream to tape
1760 devices, or create files of specified sizes to fit onto cd or dvd media.
1762 Each archive type is specified by a BackupPC host with its XferMethod
1763 set to 'archive'. This allows for multiple configurations at sites where
1764 there might be a combination of tape and cd/dvd backups being made.
1766 BackupPC provides a menu that allows one or more hosts to be archived.
1767 The most recent backup of each host is archived using BackupPC_tarCreate,
1768 and the output is optionally compressed and split into fixed-sized
1771 The archive for each host is done by default using
1772 __INSTALLDIR__/BackupPC_archiveHost. This script can be copied
1773 and customized as needed.
1775 =head2 Configuring an Archive Host
1777 To create an Archive Host, add it to the hosts file just as any other host
1778 and call it a name that best describes the type of archive, e.g. ArchiveDLT
1780 To tell BackupPC that the Host is for Archives, create a config.pl file in
1781 the Archive Hosts's pc directory, adding the following line:
1783 $Conf{XferMethod} = 'archive';
1785 To further customise the archive's parameters you can adding the changed
1786 parameters in the host's config.pl file. The parameters are explained in
1787 the config.pl file. Parameters may be fixed or the user can be allowed
1788 to change them (eg: output device).
1790 The per-host archive command is $Conf{ArchiveClientCmd}. By default
1793 __INSTALLDIR__/BackupPC_archiveHost
1795 which you can copy and customize as necessary.
1797 =head2 Starting an Archive
1799 In the web interface, click on the Archive Host you wish to use. You will see a
1800 list of previous archives and a summary on each. By clicking the "Start Archive"
1801 button you are presented with the list of hosts and the approximate backup size
1802 (note this is raw size, not projected compressed size) Select the hosts you wish
1803 to archive and press the "Archive Selected Hosts" button.
1805 The next screen allows you to adjust the parameters for this archive run.
1806 Press the "Start the Archive" to start archiving the selected hosts with the
1807 parameters displayed.
1809 =head1 BackupPC Design
1811 =head2 Some design issues
1815 =item Pooling common files
1817 To quickly see if a file is already in the pool, an MD5 digest of the
1818 file length and contents is used as the file name in the pool. This
1819 can't guarantee a file is identical: it just reduces the search to
1820 often a single file or handful of files. A complete file comparison
1821 is always done to verify if two files are really the same.
1823 Identical files on multiples backups are represented by hard links.
1824 Hardlinks are used so that identical files all refer to the same
1825 physical file on the server's disk. Also, hard links maintain
1826 reference counts so that BackupPC knows when to delete unused files
1829 For the computer-science majors among you, you can think of the pooling
1830 system used by BackupPC as just a chained hash table stored on a (big)
1833 =item The hashing function
1835 There is a tradeoff between how much of file is used for the MD5 digest
1836 and the time taken comparing all the files that have the same hash.
1838 Using the file length and just the first 4096 bytes of the file for the
1839 MD5 digest produces some repetitions. One example: with 900,000 unique
1840 files in the pool, this hash gives about 7,000 repeated files, and in
1841 the worst case 500 files have the same hash. That's not bad: we only
1842 have to do a single file compare 99.2% of the time. But in the worst
1843 case we have to compare as many as 500 files checking for a match.
1845 With a modest increase in CPU time, if we use the file length and the
1846 first 256K of the file we now only have 500 repeated files and in the
1847 worst case around 20 files have the same hash. Furthermore, if we
1848 instead use the first and last 128K of the file (more specifically, the
1849 first and eighth 128K chunks for files larger than 1MB) we get only 300
1850 repeated files and in the worst case around 20 files have the same hash.
1852 Based on this experimentation, this is the hash function used by BackupPC.
1853 It is important that you don't change the hash function after files
1854 are already in the pool. Otherwise your pool will grow to twice the
1855 size until all the old backups (and all the old files with old hashes)
1860 BackupPC supports compression. It uses the deflate and inflate methods
1861 in the Compress::Zlib module, which is based on the zlib compression
1862 library (see L<http://www.gzip.org/zlib/>).
1864 The $Conf{CompressLevel} setting specifies the compression level to use.
1865 Zero (0) means no compression. Compression levels can be from 1 (least
1866 cpu time, slightly worse compression) to 9 (most cpu time, slightly
1867 better compression). The recommended value is 3. Changing it to 5, for
1868 example, will take maybe 20% more cpu time and will get another 2-3%
1869 additional compression. Diminishing returns set in above 5. See the zlib
1870 documentation for more information about compression levels.
1872 BackupPC implements compression with minimal CPU load. Rather than
1873 compressing every incoming backup file and then trying to match it
1874 against the pool, BackupPC computes the MD5 digest based on the
1875 uncompressed file, and matches against the candidate pool files by
1876 comparing each uncompressed pool file against the incoming backup file.
1877 Since inflating a file takes roughly a factor of 10 less CPU time than
1878 deflating there is a big saving in CPU time.
1880 The combination of pooling common files and compression can yield
1881 a factor of 8 or more overall saving in backup storage.
1885 =head2 BackupPC operation
1887 BackupPC reads the configuration information from
1888 __TOPDIR__/conf/config.pl. It then runs and manages all the backup
1889 activity. It maintains queues of pending backup requests, user backup
1890 requests and administrative commands. Based on the configuration various
1891 requests will be executed simultaneously.
1893 As specified by $Conf{WakeupSchedule}, BackupPC wakes up periodically
1894 to queue backups on all the PCs. This is a four step process:
1900 For each host and DHCP address backup requests are queued on the
1901 background command queue.
1905 For each PC, BackupPC_dump is forked. Several of these may be run in
1906 parallel, based on the configuration. First a ping is done to see if
1907 the machine is alive. If this is a DHCP address, nmblookup is run to
1908 get the netbios name, which is used as the host name. If DNS lookup
1909 fails, $Conf{NmbLookupFindHostCmd} is run to find the IP address from
1910 the host name. The file __TOPDIR__/pc/$host/backups is read to decide
1911 whether a full or incremental backup needs to be run. If no backup is
1912 scheduled, or the ping to $host fails, then BackupPC_dump exits.
1914 The backup is done using the specified XferMethod. Either samba's smbclient
1915 or tar over ssh/rsh/nfs piped into BackupPC_tarExtract, or rsync over ssh/rsh
1916 is run, or rsyncd is connected to, with the incoming data
1917 extracted to __TOPDIR__/pc/$host/new. The XferMethod output is put
1918 into __TOPDIR__/pc/$host/XferLOG.
1920 The letter in the XferLOG file shows the type of object, similar to the
1921 first letter of the modes displayed by ls -l:
1925 b -> block special file
1926 c -> character special file
1927 p -> pipe file (fifo)
1928 nothing -> regular file
1936 new for this backup (ie: directory or file not in pool)
1940 found a match in the pool
1944 file is identical to previous backup (contents were
1945 checksummed and verified during full dump).
1949 file skipped in incremental because attributes are the
1950 same (only displayed if $Conf{XferLogLevel} >= 2).
1954 As BackupPC_tarExtract extracts the files from smbclient or tar, or as
1955 rsync runs, it checks each file in the backup to see if it is identical
1956 to an existing file from any previous backup of any PC. It does this
1957 without needed to write the file to disk. If the file matches an
1958 existing file, a hardlink is created to the existing file in the pool.
1959 If the file does not match any existing files, the file is written to
1960 disk and the file name is saved in __TOPDIR__/pc/$host/NewFileList for
1961 later processing by BackupPC_link. BackupPC_tarExtract and rsync can handle
1962 arbitrarily large files and multiple candidate matching files without
1963 needing to write the file to disk in the case of a match. This
1964 significantly reduces disk writes (and also reads, since the pool file
1965 comparison is done disk to memory, rather than disk to disk).
1967 Based on the configuration settings, BackupPC_dump checks each
1968 old backup to see if any should be removed. Any expired backups
1969 are moved to __TOPDIR__/trash for later removal by BackupPC_trashClean.
1973 For each complete, good, backup, BackupPC_link is run.
1974 To avoid race conditions as new files are linked into the
1975 pool area, only a single BackupPC_link program runs
1976 at a time and the rest are queued.
1978 BackupPC_link reads the NewFileList written by BackupPC_dump and
1979 inspects each new file in the backup. It re-checks if there is a
1980 matching file in the pool (another BackupPC_link
1981 could have added the file since BackupPC_dump checked). If so, the file
1982 is removed and replaced by a hard link to the existing file. If the file
1983 is new, a hard link to the file is made in the pool area, so that this
1984 file is available for checking against each new file and new backup.
1986 Then, if $Conf{IncrFill} is set (note that the default setting is
1987 off), for each incremental backup, hard links are made in the new
1988 backup to all files that were not extracted during the incremental
1989 backups. The means the incremental backup looks like a complete
1990 image of the PC (with the exception that files that were removed on
1991 the PC since the last full backup will still appear in the backup
1994 The CGI interface knows how to merge unfilled incremental backups will
1995 the most recent prior filled (full) backup, giving the incremental
1996 backups a filled appearance. The default for $Conf{IncrFill} is off,
1997 since there is no need to fill incremental backups. This saves
1998 some level of disk activity, since lots of extra hardlinks are no
1999 longer needed (and don't have to be deleted when the backup expires).
2003 BackupPC_trashClean is always run in the background to remove any
2004 expired backups. Every 5 minutes it wakes up and removes all the files
2005 in __TOPDIR__/trash.
2007 Also, once each night, BackupPC_nightly is run to complete some additional
2008 administrative tasks, such as cleaning the pool. This involves removing
2009 any files in the pool that only have a single hard link (meaning no backups
2010 are using that file). Again, to avoid race conditions, BackupPC_nightly
2011 is only run when there are no BackupPC_dump or BackupPC_link processes
2012 running. Therefore, when it is time to run BackupPC_nightly, no new
2013 backups are started and BackupPC waits until all backups have finished.
2014 Then BackupPC_nightly is run, and until it finishes no new backups are
2015 started. If BackupPC_nightly takes too long to run, the settings
2016 $Conf{MaxBackupPCNightlyJobs} and $Conf{BackupPCNightlyPeriod} can
2017 be used to run several BackupPC_nightly processes in parallel, and
2018 to split its job over several nights.
2022 BackupPC also listens for TCP connections on $Conf{ServerPort}, which
2023 is used by the CGI script BackupPC_Admin for status reporting and
2024 user-initiated backup or backup cancel requests.
2026 =head2 Storage layout
2028 BackupPC resides in three directories:
2032 =item __INSTALLDIR__
2034 Perl scripts comprising BackupPC reside in __INSTALLDIR__/bin,
2035 libraries are in __INSTALLDIR__/lib and documentation
2036 is in __INSTALLDIR__/doc.
2040 The CGI script BackupPC_Admin resides in this cgi binary directory.
2044 All of BackupPC's data (PC backup images, logs, configuration information)
2045 is stored below this directory.
2049 Below __TOPDIR__ are several directories:
2053 =item __TOPDIR__/conf
2055 The directory __TOPDIR__/conf contains:
2061 Configuration file. See L<Configuration file|configuration file>
2062 below for more details.
2066 Hosts file, which lists all the PCs to backup.
2070 =item __TOPDIR__/log
2072 The directory __TOPDIR__/log contains:
2078 Current (today's) log file output from BackupPC.
2080 =item LOG.0 or LOG.0.z
2082 Yesterday's log file output. Log files are aged daily and compressed
2083 (if compression is enabled), and old LOG files are deleted.
2087 Contains BackupPC's process id.
2091 A summary of BackupPC's status written periodically by BackupPC so
2092 that certain state information can be maintained if BackupPC is
2093 restarted. Should not be edited.
2095 =item UserEmailInfo.pl
2097 A summary of what email was last sent to each user, and when the
2098 last email was sent. Should not be edited.
2102 =item __TOPDIR__/trash
2104 Any directories and files below this directory are periodically deleted
2105 whenever BackupPC_trashClean checks. When a backup is aborted or when an
2106 old backup expires, BackupPC_dump simply moves the directory to
2107 __TOPDIR__/trash for later removal by BackupPC_trashClean.
2109 =item __TOPDIR__/pool
2111 All uncompressed files from PC backups are stored below __TOPDIR__/pool.
2112 Each file's name is based on the MD5 hex digest of the file contents.
2113 Specifically, for files less than 256K, the file length and the entire
2114 file is used. For files up to 1MB, the file length and the first and
2115 last 128K are used. Finally, for files longer than 1MB, the file length,
2116 and the first and eighth 128K chunks for the file are used.
2118 Each file is stored in a subdirectory X/Y/Z, where X, Y, Z are the
2119 first 3 hex digits of the MD5 digest.
2121 For example, if a file has an MD5 digest of 123456789abcdef0,
2122 the file is stored in __TOPDIR__/pool/1/2/3/123456789abcdef0.
2124 The MD5 digest might not be unique (especially since not all the file's
2125 contents are used for files bigger than 256K). Different files that have
2126 the same MD5 digest are stored with a trailing suffix "_n" where n is
2127 an incrementing number starting at 0. So, for example, if two additional
2128 files were identical to the first, except the last byte was different,
2129 and assuming the file was larger than 1MB (so the MD5 digests are the
2130 same but the files are actually different), the three files would be
2133 __TOPDIR__/pool/1/2/3/123456789abcdef0
2134 __TOPDIR__/pool/1/2/3/123456789abcdef0_0
2135 __TOPDIR__/pool/1/2/3/123456789abcdef0_1
2137 Both BackupPC_dump (actually, BackupPC_tarExtract) and BackupPC_link are
2138 responsible for checking newly backed up files against the pool. For
2139 each file, the MD5 digest is used to generate a file name in the pool
2140 directory. If the file exists in the pool, the contents are compared.
2141 If there is no match, additional files ending in "_n" are checked.
2142 (Actually, BackupPC_tarExtract compares multiple candidate files in
2143 parallel.) If the file contents exactly match, the file is created by
2144 simply making a hard link to the pool file (this is done by
2145 BackupPC_tarExtract as the backup proceeds). Otherwise,
2146 BackupPC_tarExtract writes the new file to disk and a new hard link is
2147 made in the pool to the file (this is done later by BackupPC_link).
2149 Therefore, every file in the pool will have at least 2 hard links
2150 (one for the pool file and one for the backup file below __TOPDIR__/pc).
2151 Identical files from different backups or PCs will all be linked to
2152 the same file. When old backups are deleted, some files in the pool
2153 might only have one link. BackupPC_nightly checks the entire pool
2154 and removes all files that have only a single link, thereby recovering
2155 the storage for that file.
2157 One other issue: zero length files are not pooled, since there are a lot
2158 of these files and on most file systems it doesn't save any disk space
2159 to turn these files into hard links.
2161 =item __TOPDIR__/cpool
2163 All compressed files from PC backups are stored below __TOPDIR__/cpool.
2164 Its layout is the same as __TOPDIR__/pool, and the hashing function
2165 is the same (and, importantly, based on the uncompressed file, not
2166 the compressed file).
2168 =item __TOPDIR__/pc/$host
2170 For each PC $host, all the backups for that PC are stored below
2171 the directory __TOPDIR__/pc/$host. This directory contains the
2178 Current log file for this PC from BackupPC_dump.
2180 =item LOG.0 or LOG.0.z
2182 Last month's log file. Log files are aged monthly and compressed
2183 (if compression is enabled), and old LOG files are deleted.
2185 =item XferERR or XferERR.z
2187 Output from the transport program (ie: smbclient, tar or rsync)
2188 for the most recent failed backup.
2192 Subdirectory in which the current backup is stored. This
2193 directory is renamed if the backup succeeds.
2195 =item XferLOG or XferLOG.z
2197 Output from the transport program (ie: smbclient, tar or rsync)
2198 for the current backup.
2200 =item nnn (an integer)
2202 Successful backups are in directories numbered sequentially starting at 0.
2204 =item XferLOG.nnn or XferLOG.nnn.z
2206 Output from the transport program (ie: smbclient, tar or rsync)
2207 corresponding to backup number nnn.
2209 =item RestoreInfo.nnn
2211 Information about restore request #nnn including who, what, when, and
2212 why. This file is in Data::Dumper format. (Note that the restore
2213 numbers are not related to the backup number.)
2215 =item RestoreLOG.nnn.z
2217 Output from smbclient, tar or rsync during restore #nnn. (Note that the restore
2218 numbers are not related to the backup number.)
2220 =item ArchiveInfo.nnn
2222 Information about archive request #nnn including who, what, when, and
2223 why. This file is in Data::Dumper format. (Note that the archive
2224 numbers are not related to the restore or backup number.)
2226 =item ArchiveLOG.nnn.z
2228 Output from archive #nnn. (Note that the archive numbers are not related
2229 to the backup or restore number.)
2233 Optional configuration settings specific to this host. Settings in this
2234 file override the main configuration file.
2238 A tab-delimited ascii table listing information about each successful
2239 backup, one per row. The columns are:
2245 The backup number, an integer that starts at 0 and increments
2246 for each successive backup. The corresponding backup is stored
2247 in the directory num (eg: if this field is 5, then the backup is
2248 stored in __TOPDIR__/pc/$host/5).
2252 Set to "full" or "incr" for full or incremental backup.
2256 Start time of the backup in unix seconds.
2260 Stop time of the backup in unix seconds.
2264 Number of files backed up (as reported by smbclient, tar or rsync).
2268 Total file size backed up (as reported by smbclient, tar or rsync).
2272 Number of files that were already in the pool
2273 (as determined by BackupPC_dump and BackupPC_link).
2277 Total size of files that were already in the pool
2278 (as determined by BackupPC_dump and BackupPC_link).
2282 Number of files that were not in the pool
2283 (as determined by BackupPC_link).
2287 Total size of files that were not in the pool
2288 (as determined by BackupPC_link).
2292 Number of errors or warnings from smbclient, tar or rsync.
2296 Number of errors from smbclient that were bad file errors (zero otherwise).
2300 Number of errors from smbclient that were bad share errors (zero otherwise).
2304 Number of errors from BackupPC_tarExtract.
2308 The compression level used on this backup. Zero or empty means no
2313 Total compressed size of files that were already in the pool
2314 (as determined by BackupPC_dump and BackupPC_link).
2318 Total compressed size of files that were not in the pool
2319 (as determined by BackupPC_link).
2323 Set if this backup has not been filled in with the most recent
2324 previous filled or full backup. See $Conf{IncrFill}.
2328 If this backup was filled (ie: noFill is 0) then this is the
2329 number of the backup that it was filled from
2333 Set if this backup has mangled file names and attributes. Always
2334 true for backups in v1.4.0 and above. False for all backups prior
2339 Set to the value of $Conf{XferMethod} when this dump was done.
2343 The level of this dump. A full dump is level 0. Currently incrementals
2344 are 1. But when multi-level incrementals are supported this will reflect
2345 each dump's incremental level.
2351 A tab-delimited ascii table listing information about each requested
2352 restore, one per row. The columns are:
2358 Restore number (matches the suffix of the RestoreInfo.nnn and
2359 RestoreLOG.nnn.z file), unrelated to the backup number.
2363 Start time of the restore in unix seconds.
2367 End time of the restore in unix seconds.
2371 Result (ok or failed).
2375 Error message if restore failed.
2379 Number of files restored.
2383 Size in bytes of the restored files.
2387 Number of errors from BackupPC_tarCreate during restore.
2391 Number of errors from smbclient, tar or rsync during restore.
2397 A tab-delimited ascii table listing information about each requested
2398 archive, one per row. The columns are:
2404 Archive number (matches the suffix of the ArchiveInfo.nnn and
2405 ArchiveLOG.nnn.z file), unrelated to the backup or restore number.
2409 Start time of the restore in unix seconds.
2413 End time of the restore in unix seconds.
2417 Result (ok or failed).
2421 Error message if archive failed.
2429 =head2 Compressed file format
2431 The compressed file format is as generated by Compress::Zlib::deflate
2432 with one minor, but important, tweak. Since Compress::Zlib::inflate
2433 fully inflates its argument in memory, it could take large amounts of
2434 memory if it was inflating a highly compressed file. For example, a
2435 200MB file of 0x0 bytes compresses to around 200K bytes. If
2436 Compress::Zlib::inflate was called with this single 200K buffer, it
2437 would need to allocate 200MB of memory to return the result.
2439 BackupPC watches how efficiently a file is compressing. If a big file
2440 has very high compression (meaning it will use too much memory when it
2441 is inflated), BackupPC calls the flush() method, which gracefully
2442 completes the current compression. BackupPC then starts another
2443 deflate and simply appends the output file. So the BackupPC compressed
2444 file format is one or more concatenated deflations/flushes. The specific
2445 ratios that BackupPC uses is that if a 6MB chunk compresses to less
2446 than 64K then a flush will be done.
2448 Back to the example of the 200MB file of 0x0 bytes. Adding flushes
2449 every 6MB adds only 200 or so bytes to the 200K output. So the
2450 storage cost of flushing is negligible.
2452 To easily decompress a BackupPC compressed file, the script
2453 BackupPC_zcat can be found in __INSTALLDIR__/bin. For each
2454 file name argument it inflates the file and writes it to stdout.
2456 =head2 Rsync checksum caching
2458 An incremental backup with rsync compares attributes on the client
2459 with the last full backup. Any files with identical attributes
2460 are skipped. A full backup with rsync sets the --ignore-times
2461 option, which causes every file to be examined independent of
2464 Each file is examined by generating block checksums (default 2K
2465 blocks) on the receiving side (that's the BackupPC side), sending
2466 those checksums to the client, where the remote rsync matches those
2467 checksums with the corresponding file. The matching blocks and new
2468 data is sent back, allowing the client file to be reassembled.
2469 A checksum for the entire file is sent to as an extra check the
2470 the reconstructed file is correct.
2472 This results in significant disk IO and computation for BackupPC:
2473 every file in a full backup, or any file with non-matching attributes
2474 in an incremental backup, needs to be uncompressed, block checksums
2475 computed and sent. Then the receiving side reassembles the file and
2476 has to verify the whole-file checksum. Even if the file is identical,
2477 prior to 2.1.0, BackupPC had to read and uncompress the file twice,
2478 once to compute the block checksums and later to verify the whole-file
2481 Starting in 2.1.0, BackupPC supports optional checksum caching,
2482 which means the block and file checksums only need to be computed
2483 once for each file. This results in a significant performance
2484 improvement. This only works for compressed pool files.
2485 It is enabled by adding
2487 '--checksum-seed=32761',
2489 to $Conf{RsyncArgs} and $Conf{RsyncRestoreArgs}.
2491 Rsync versions prior to and including rsync-2.6.2 need a small patch to
2492 add support for the --checksum-seed option. This patch is available in
2493 the cygwin-rsyncd package at L<http://backuppc.sourceforge.net>.
2494 This patch is already included in rsync CVS, so it will be standard
2495 in future versions of rsync.
2497 When this option is present, BackupPC will add block and file checksums
2498 to the compressed pool file the next time a pool file is used and it
2499 doesn't already have cached checksums. The first time a new file is
2500 written to the pool, the checksums are not appended. The next time
2501 checksums are needed for a file, they are computed and added. So the
2502 full performance benefit of checksum caching won't be noticed until the
2503 third time a pool file is used (eg: the third full backup).
2505 With checksum caching enabled, there is a risk that should a file's contents
2506 in the pool be corrupted due to a disk problem, but the cached checksums
2507 are still correct, the corruption will not be detected by a full backup,
2508 since the file contents are no longer read and compared. To reduce the
2509 chance that this remains undetected, BackupPC can recheck cached checksums
2510 for a fraction of the files. This fraction is set with the
2511 $Conf{RsyncCsumCacheVerifyProb} setting. The default value of 0.01 means
2512 that 1% of the time a file's checksums are read, the checksums are verified.
2513 This reduces performance slightly, but, over time, ensures that files
2514 contents are in sync with the cached checksums.
2516 The format of the cached checksum data can be discovered by looking at
2517 the code. Basically, the first byte of the compressed file is changed
2518 to denote that checksums are appended. The block and file checksum
2519 data, plus some other information and magic word, are appended to the
2520 compressed file. This allows the cache update to be done in-place.
2522 =head2 File name mangling
2524 Backup file names are stored in "mangled" form. Each node of
2525 a path is preceded by "f" (mnemonic: file), and special characters
2526 (\n, \r, % and /) are URI-encoded as "%xx", where xx is the ascii
2527 character's hex value. So c:/craig/example.txt is now stored as
2528 fc/fcraig/fexample.txt.
2530 This was done mainly so meta-data could be stored alongside the backup
2531 files without name collisions. In particular, the attributes for the
2532 files in a directory are stored in a file called "attrib", and mangling
2533 avoids file name collisions (I discarded the idea of having a duplicate
2534 directory tree for every backup just to store the attributes). Other
2535 meta-data (eg: rsync checksums) could be stored in file names preceded
2536 by, eg, "c". There are two other benefits to mangling: the share name
2537 might contain "/" (eg: "/home/craig" for tar transport), and I wanted
2538 that represented as a single level in the storage tree. Secondly, as
2539 files are written to NewFileList for later processing by BackupPC_link,
2540 embedded newlines in the file's path will cause problems which are
2541 avoided by mangling.
2543 The CGI script undoes the mangling, so it is invisible to the user.
2544 Old (unmangled) backups are still supported by the CGI
2547 =head2 Special files
2549 Linux/unix file systems support several special file types: symbolic
2550 links, character and block device files, fifos (pipes) and unix-domain
2551 sockets. All except unix-domain sockets are supported by BackupPC
2552 (there's no point in backing up or restoring unix-domain sockets since
2553 they only have meaning after a process creates them). Symbolic links are
2554 stored as a plain file whose contents are the contents of the link (not
2555 the file it points to). This file is compressed and pooled like any
2556 normal file. Character and block device files are also stored as plain
2557 files, whose contents are two integers separated by a comma; the numbers
2558 are the major and minor device number. These files are compressed and
2559 pooled like any normal file. Fifo files are stored as empty plain files
2560 (which are not pooled since they have zero size). In all cases, the
2561 original file type is stored in the attrib file so it can be correctly
2564 Hardlinks are also supported. When GNU tar first encounters a file with
2565 more than one link (ie: hardlinks) it dumps it as a regular file. When
2566 it sees the second and subsequent hardlinks to the same file, it dumps
2567 just the hardlink information. BackupPC correctly recognizes these
2568 hardlinks and stores them just like symlinks: a regular text file
2569 whose contents is the path of the file linked to. The CGI script
2570 will download the original file when you click on a hardlink.
2572 Also, BackupPC_tarCreate has enough magic to re-create the hardlinks
2573 dynamically based on whether or not the original file and hardlinks
2574 are both included in the tar file. For example, imagine a/b/x is a
2575 hardlink to a/c/y. If you use BackupPC_tarCreate to restore directory
2576 a, then the tar file will include a/b/x as the original file and a/c/y
2577 will be a hardlink to a/b/x. If, instead you restore a/c, then the
2578 tar file will include a/c/y as the original file, not a hardlink.
2580 =head2 Attribute file format
2582 The unix attributes for the contents of a directory (all the files and
2583 directories in that directory) are stored in a file called attrib.
2584 There is a single attrib file for each directory in a backup.
2585 For example, if c:/craig contains a single file c:/craig/example.txt,
2586 that file would be stored as fc/fcraig/fexample.txt and there would be an
2587 attribute file in fc/fcraig/attrib (and also fc/attrib and ./attrib).
2588 The file fc/fcraig/attrib would contain a single entry containing the
2589 attributes for fc/fcraig/fexample.txt.
2591 The attrib file starts with a magic number, followed by the
2592 concatenation of the following information for each file:
2598 File name length in perl's pack "w" format (variable length base 128).
2606 The unix file type, mode, uid, gid and file size divided by 4GB and
2607 file size modulo 4GB (type mode uid gid sizeDiv4GB sizeMod4GB),
2608 in perl's pack "w" format (variable length base 128).
2612 The unix mtime (unix seconds) in perl's pack "N" format (32 bit integer).
2616 The attrib file is also compressed if compression is enabled.
2617 See the lib/BackupPC/Attrib.pm module for full details.
2619 Attribute files are pooled just like normal backup files. This saves
2620 space if all the files in a directory have the same attributes across
2621 multiple backups, which is common.
2623 =head2 Optimizations
2625 BackupPC doesn't care about the access time of files in the pool
2626 since it saves attribute meta-data separate from the files. Since
2627 BackupPC mostly does reads from disk, maintaining the access time of
2628 files generates a lot of unnecessary disk writes. So, provided
2629 BackupPC has a dedicated data disk, you should consider mounting
2630 BackupPC's data directory with the noatime attribute (see mount(1)).
2634 BackupPC isn't perfect (but it is getting better). Please see
2635 L<http://backuppc.sourceforge.net/faq/limitations.html> for a
2636 discussion of some of BackupPC's limitations.
2638 =head2 Security issues
2640 Please see L<http://backuppc.sourceforge.net/faq/security.html> for a
2641 discussion of some of various security issues.
2643 =head1 Configuration File
2645 The BackupPC configuration file resides in __TOPDIR__/conf/config.pl.
2646 Optional per-PC configuration files reside in __TOPDIR__/pc/$host/config.pl.
2647 This file can be used to override settings just for a particular PC.
2649 =head2 Modifying the main configuration file
2651 The configuration file is a perl script that is executed by BackupPC, so
2652 you should be careful to preserve the file syntax (punctuation, quotes
2653 etc) when you edit it. It is recommended that you use CVS, RCS or some
2654 other method of source control for changing config.pl.
2656 BackupPC reads or re-reads the main configuration file and
2657 the hosts file in three cases:
2667 When BackupPC is sent a HUP (-1) signal. Assuming you installed the
2668 init.d script, you can also do this with "/etc/init.d/backuppc reload".
2672 When the modification time of config.pl file changes. BackupPC
2673 checks the modification time once during each regular wakeup.
2677 Whenever you change the configuration file you can either do
2678 a kill -HUP BackupPC_pid or simply wait until the next regular
2681 Each time the configuration file is re-read a message is reported in the
2682 LOG file, so you can tail it (or view it via the CGI interface) to make
2683 sure your kill -HUP worked. Errors in parsing the configuration file are
2684 also reported in the LOG file.
2686 The optional per-PC configuration file (__TOPDIR__/pc/$host/config.pl)
2687 is read whenever it is needed by BackupPC_dump, BackupPC_link and others.
2689 =head2 Configuration file includes
2691 If you have a heterogeneous set of clients (eg: a variety of WinXX and
2692 linux/unix machines) you will need to create host-specific config.pl files
2693 for some or all of these machines to customize the default settings from
2694 the master config.pl file (at a minimum to set $Conf{XferMethod}).
2696 Since the config.pl file is just regular perl code, you can include
2697 one config file from another. For example, imagine you had three general
2698 classes of machines: WinXX desktops, linux machines in the DMZ and
2699 linux desktops. You could create three config files in __TOPDIR__/conf:
2701 __TOPDIR__/conf/ConfigWinDesktop.pl
2702 __TOPDIR__/conf/ConfigLinuxDMZ.pl
2703 __TOPDIR__/conf/ConfigLinuxDesktop.pl
2705 From each client's directory you can either add a symbolic link to
2706 the appropriate config file:
2708 cd __TOPDIR__/pc/$host
2709 ln -s ../../conf/ConfigWinDesktop.pl config.pl
2711 or, better yet, create a config.pl file in __TOPDIR__/pc/$host
2712 that includes the default config.pl file using perl's "do"
2715 do "__TOPDIR__/conf/ConfigWinDesktop.pl";
2717 This alternative allows you to set other configuration options
2718 specific to each host after the "do" command (perhaps even
2719 overriding the settings in the included file).
2721 Note that you could also include snippets of configuration settings
2722 from the main configuration file. However, be aware that the
2723 modification-time checking that BackupPC does only applies to the
2724 main configuration file: if you change one of the included files,
2725 BackupPC won't notice. You will need to either touch the main
2726 configuration file too, or send BackupPC a HUP (-1) signal.
2728 =head1 Configuration Parameters
2730 The configuration parameters are divided into five general groups.
2731 The first group (general server configuration) provides general
2732 configuration for BackupPC. The next two groups describe what to
2733 backup, when to do it, and how long to keep it. The fourth group
2734 are settings for email reminders, and the final group contains
2735 settings for the CGI interface.
2737 All configuration settings in the second through fifth groups can
2738 be overridden by the per-PC config.pl file.
2742 =head1 Version Numbers
2744 Starting with v1.4.0 BackupPC uses a X.Y.Z version numbering system,
2745 instead of X.0Y. The first digit is for major new releases, the middle
2746 digit is for significant feature releases and improvements (most of
2747 the releases have been in this category), and the last digit is for
2748 bug fixes. You should think of the old 1.00, 1.01, 1.02 and 1.03 as
2749 1..0, 1.1.0, 1.2.0 and 1.3.0.
2751 Additionally, patches might be made available. A patched version
2752 number is of the form X.Y.ZplN (eg: 2.1.0pl2), where N is the
2757 Craig Barratt <cbarratt@users.sourceforge.net>
2759 See L<http://backuppc.sourceforge.net>.
2763 Copyright (C) 2001-2005 Craig Barratt
2767 Ryan Kucera contributed the directory navigation code and images
2768 for v1.5.0. He contributed the first skeleton of BackupPC_restore.
2769 He also added a significant revision to the CGI interface, including
2770 CSS tags, in v2.1.0, and designed the BackupPC logo.
2772 Xavier Nicollet, with additions from Guillaume Filion, added the
2773 internationalization (i18n) support to the CGI interface for v2.0.0.
2774 Xavier provided the French translation fr.pm, with additions from
2777 Guillaume Filion wrote BackupPC_zipCreate and added the CGI support
2778 for zip download, in addition to some CGI cleanup, for v1.5.0.
2779 Guillaume continues to support fr.pm updates for each new version.
2781 Josh Marshall implemented the Archive feature in v2.1.0.
2783 Ludovic Drolez supports the BackupPC Debian package.
2785 Javier Gonzalez provided the Spanish translation, es.pm for v2.0.0.
2787 Manfred Herrmann provided the German translation, de.pm for v2.0.0.
2788 Manfred continues to support de.pm updates for each new version,
2789 together with some help frmo Ralph Paßgang.
2791 Lorenzo Cappelletti provided the Italian translation, it.pm for v2.1.0.
2793 Lieven Bridts provided the Dutch translation, nl.pm, for v2.1.0,
2794 with some tweaks from Guus Houtzager.
2796 Reginaldo Ferreira provided the Portuguese Brazillian translation
2797 pt_br.pm for v2.2.0.
2799 Many people have reported bugs, made useful suggestions and helped
2800 with testing; see the ChangeLog and the mail lists.
2802 Your name could appear here in the next version!
2806 This program is free software; you can redistribute it and/or modify it
2807 under the terms of the GNU General Public License as published by the
2808 Free Software Foundation; either version 2 of the License, or (at your
2809 option) any later version.
2811 This program is distributed in the hope that it will be useful,
2812 but WITHOUT ANY WARRANTY; without even the implied warranty of
2813 MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
2814 General Public License for more details.
2816 You should have received a copy of the GNU General Public License in the
2817 LICENSE file along with this program; if not, write to the Free Software
2818 Foundation, Inc., 59 Temple Place, Suite 330, Boston, MA 02111-1307 USA.