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, WinXX, and MacOSX PCs, desktops and laptops to a server's
10 disk. 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
38 the current status, edit configuration, add/delete hosts, view log
39 files, and allows users to initiate and cancel backups and browse
40 and restore files from backups.
44 The http/cgi user interface has internationalization (i18n) support,
45 currently providing English, French, German, Spanish, Italian,
46 Dutch and Portuguese-Brazilian.
50 No client-side software is needed. On WinXX the standard smb protocol is
51 used to extract backup data. On linux, unix or MacOSX clients, rsync or
52 tar (over ssh/rsh/nfs) is used to extract backup data. Alternatively,
53 rsync can also be used on WinXX (using cygwin), and Samba could be
54 installed on the linux or unix client to provide smb shares).
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
111 since the last successful full or incremental backup. Starting
112 in BackupPC 3.0 multi-level incrementals are supported.
113 A full backup has level 0. A new incremental of level N will
114 backup all files that have changed since the most recent backup
115 of a lower level. $Conf{IncrLevels} is used to specify the
116 level of each successive incremental. The default value is
117 all level 1, which makes the behavior the same as earlier
118 versions of BackupPC: each incremental will back up all the
119 files that changed since the last full (level 0).
121 For SMB and tar, BackupPC uses the modification time (mtime) to
122 determine which files have changed since the last lower-level
123 backup. That mean SMB and tar incrementals are not able to detect
124 deleted files, renamed files or new files whose modification time
125 is prior to the last lower-level backup.
127 Rsync is more clever: any files whose attributes have changed (ie: uid,
128 gid, mtime, modes, size) since the last full are backed up. Deleted,
129 new files and renamed files are detected by Rsync incrementals.
131 BackupPC can also be configured to keep a certain number of incremental
132 backups, and to keep a smaller number of very old incremental backups.
133 If multi-level incrementals are specified then it is likely that
134 more incrementals will need to be kept since lower-level incrementals
135 (and the full backup) are needed to reconstruct a higher-level
138 BackupPC "fills-in" incremental backups when browsing or restoring,
139 based on the levels of each backup, giving every backup a "full"
140 appearance. This makes browsing and restoring backups much easier:
141 you can restore from any one backup independent of whether it was
142 an incremental or full.
146 When a full backup fails or is canceled, and some files have already
147 been backed up, BackupPC keeps a partial backup containing just the
148 files that were backed up successfully. The partial backup is removed
149 when the next successful backup completes, or if another full backup
150 fails resulting in a newer partial backup. A failed full backup
151 that has not backed up any files, or any failed incremental backup,
152 is removed; no partial backup is saved in these cases.
154 The partial backup may be browsed or used to restore files just like
155 a successful full or incremental backup.
157 With the rsync transfer method the partial backup is used to resume
158 the next full backup, avoiding the need to retransfer the file data
159 already in the partial backup.
161 =item Identical Files
163 BackupPC pools identical files using hardlinks. By "identical
164 files" we mean files with identical contents, not necessary the
165 same permissions, ownership or modification time. Two files might
166 have different permissions, ownership, or modification time but
167 will still be pooled whenever the contents are identical. This
168 is possible since BackupPC stores the file meta-data (permissions,
169 ownership, and modification time) separately from the file contents.
173 Based on your site's requirements you need to decide what your backup
174 policy is. BackupPC is not designed to provide exact re-imaging of
175 failed disks. See L<Limitations|limitations> for more information.
176 However, the addition of tar transport for linux/unix clients, plus
177 full support for special file types and unix attributes in v1.4.0
178 likely means an exact image of a linux/unix file system can be made.
180 BackupPC saves backups onto disk. Because of pooling you can relatively
181 economically keep several weeks of old backups.
183 At some sites the disk-based backup will be adequate, without a
184 secondary tape backup. This system is robust to any single failure: if a
185 client disk fails or loses files, the BackupPC server can be used to
186 restore files. If the server disk fails, BackupPC can be restarted on a
187 fresh file system, and create new backups from the clients. The chance
188 of the server disk failing can be made very small by spending more money
189 on increasingly better RAID systems. However, there is still the risk
190 of catastrophic events like fires or earthquakes that can destroy
191 both the BackupPC server and the clients it is backing up if they
192 are physically nearby.
194 Some sites might choose to do periodic backups to tape or cd/dvd.
195 This backup can be done perhaps weekly using the archive function of
198 Other users have reported success with removable disks to rotate the
199 BackupPC data drives, or using rsync to mirror the BackupPC data pool
208 =item BackupPC home page
210 The BackupPC Open Source project is hosted on SourceForge. The
211 home page can be found at:
213 http://backuppc.sourceforge.net
215 This page has links to the current documentation, the SourceForge
216 project page and general information.
218 =item SourceForge project
220 The SourceForge project page is at:
222 http://sourceforge.net/projects/backuppc
224 This page has links to the current releases of BackupPC.
228 BackupPC has a FAQ at L<http://backuppc.sourceforge.net/faq>.
232 Three BackupPC mailing lists exist for announcements (backuppc-announce),
233 developers (backuppc-devel), and a general user list for support, asking
234 questions or any other topic relevant to BackupPC (backuppc-users).
236 The lists are archived on SourceForge and Gmane. The SourceForge lists
237 are not always up to date and the searching is limited, so Gmane is
238 a good alternative. See:
240 http://news.gmane.org/index.php?prefix=gmane.comp.sysutils.backup.backuppc
241 http://sourceforge.net/mailarchive/forum.php?forum=backuppc-users
243 You can subscribe to these lists by visiting:
245 http://lists.sourceforge.net/lists/listinfo/backuppc-announce
246 http://lists.sourceforge.net/lists/listinfo/backuppc-users
247 http://lists.sourceforge.net/lists/listinfo/backuppc-devel
249 The backuppc-announce list is moderated and is used only for
250 important announcements (eg: new versions). It is low traffic.
251 You only need to subscribe to one of backuppc-announce and
252 backuppc-users: backuppc-users also receives any messages on
255 The backuppc-devel list is only for developers who are working on BackupPC.
256 Do not post questions or support requests there. But detailed technical
257 discussions should happen on this list.
259 To post a message to the backuppc-users list, send an email to
261 backuppc-users@lists.sourceforge.net
263 Do not send subscription requests to this address!
265 =item Other Programs of Interest
267 If you want to mirror linux or unix files or directories to a remote server
268 you should use rsync, L<http://rsync.samba.org>. BackupPC uses
269 rsync as a transport mechanism; if you are already an rsync user you
270 can think of BackupPC as adding efficient storage (compression and
271 pooling) and a convenient user interface to rsync.
273 Two popular open source packages that do tape backup are
274 Amanda (L<http://www.amanda.org>)
275 and Bacula (L<http://www.bacula.org>).
276 Amanda can also backup WinXX machines to tape using samba.
277 These packages can be used as back ends to BackupPC to backup the
278 BackupPC server data to tape.
280 Various programs and scripts use rsync to provide hardlinked backups.
281 See, for example, Mike Rubel's site (L<http://www.mikerubel.org/computers/rsync_snapshots>),
282 JW Schultz's dirvish (L<http://www.dirvish.org/>),
283 Ben Escoto's rdiff-backup (L<http://www.nongnu.org/rdiff-backup>),
284 and John Bowman's rlbackup (L<http://www.math.ualberta.ca/imaging/rlbackup>).
286 Unison is a utility that can do two-way, interactive, synchronization.
287 See L<http://freshmeat.net/projects/unison>. An external wrapper around
288 rsync that maintains transfer data to enable two-way synchronization is
289 drsync; see L<http://freshmeat.net/projects/drsync>.
291 BackupPC provides many additional features, such as compressed storage,
292 hardlinking any matching files (rather than just files with the same name),
293 and storing special files without root privileges. But these other programs
294 provide simple, effective and fast solutions and are definitely worthy of
301 The new features planned for future releases of BackupPC
302 are at L<http://backuppc.sourceforge.net/faq/roadMap.html>.
304 Comments and suggestions are welcome.
308 BackupPC is free. I work on BackupPC because I enjoy doing it and I like
309 to contribute to the open source community.
311 BackupPC already has more than enough features for my own needs. The
312 main compensation for continuing to work on BackupPC is knowing that
313 more and more people find it useful. So feedback is certainly
314 appreciated, both positive and negative.
316 Beyond being a satisfied user and telling other people about it, everyone
317 is encouraged to add links to L<http://backuppc.sourceforge.net>
318 (I'll see them via Google) or otherwise publicize BackupPC. Unlike
319 the commercial products in this space, I have a zero budget (in both
320 time and money) for marketing, PR and advertising, so it's up to
321 all of you! Feel free to vote for BackupPC at
322 L<http://freshmeat.net/projects/backuppc>.
324 Also, everyone is encouraged to contribute patches, bug reports, feature
325 and design suggestions, new code, FAQs, and documentation corrections or
326 improvements. Answering questions on the mail list is a big help too.
328 =head1 Installing BackupPC
338 A linux, solaris, or unix based server with a substantial amount of free
339 disk space (see the next section for what that means). The CPU and disk
340 performance on this server will determine how many simultaneous backups
341 you can run. You should be able to run 4-8 simultaneous backups on a
342 moderately configured server.
344 Several users have reported significantly better performance using
345 reiser compared to ext3 for the BackupPC data file system. It is
346 also recommended you consider either an LVM or raid setup (either
347 in HW or SW; eg: 3Ware RAID5) so that you can expand the
348 file system as necessary.
350 When BackupPC starts with an empty pool, all the backup data will be
351 written to the pool on disk. After more backups are done, a higher
352 percentage of incoming files will already be in the pool. BackupPC is
353 able to avoid writing to disk new files that are already in the pool.
354 So over time disk writes will reduce significantly (by perhaps a factor
355 of 20 or more), since eventually 95% or more of incoming backup files
356 are typically in the pool. Disk reads from the pool are still needed to
357 do file compares to verify files are an exact match. So, with a mature
358 pool, if a relatively fast client generates data at say 1MB/sec, and you
359 run 4 simultaneous backups, there will be an average server disk load of
360 about 4MB/sec reads and 0.2MB/sec writes (assuming 95% of the incoming
361 files are in the pool). These rates will be perhaps 40% lower if
366 Perl version 5.8.0 or later. If you don't have perl, please
367 see L<http://www.cpan.org>.
371 Perl modules Compress::Zlib, Archive::Zip and File::RsyncP. Try "perldoc
372 Compress::Zlib" and "perldoc Archive::Zip" to see if you have these
373 modules. If not, fetch them from L<http://www.cpan.org> and see the
374 instructions below for how to build and install them.
376 The File::RsyncP module is available from L<http://perlrsync.sourceforge.net>
377 or CPAN. You'll need to install the File::RsyncP module if you want to use
378 Rsync as a transport method.
382 If you are using smb to backup WinXX machines you need smbclient and
383 nmblookup from the samba package. You will also need nmblookup if
384 you are backing up linux/unix DHCP machines. See L<http://www.samba.org>.
385 Samba versions 3.x are stable and now recommended instead of 2.x.
387 See L<http://www.samba.org> for source and binaries. It's pretty easy to
388 fetch and compile samba, and just grab smbclient and nmblookup, without
389 doing the installation. Alternatively, L<http://www.samba.org> has binary
390 distributions for most platforms.
394 If you are using tar to backup linux/unix machines you should have version
395 1.13.7 at a minimum, with version 1.13.20 or higher recommended. Use
396 "tar --version" to check your version. Various GNU mirrors have the newest
397 versions of tar, see for example L<http://www.funet.fi/pub/gnu/alpha/gnu/tar>.
398 As of July 2006 the latest version is 1.15.1.
402 If you are using rsync to backup linux/unix machines you should have
403 version 2.6.3 or higher on each client machine. See
404 L<http://rsync.samba.org>. Use "rsync --version" to check your version.
406 For BackupPC to use Rsync you will also need to install the perl
407 File::RsyncP module, which is available from
408 L<http://perlrsync.sourceforge.net>.
409 Version 0.68 or later is required.
413 The Apache web server, see L<http://www.apache.org>, preferably built
414 with mod_perl support.
418 =head2 What type of storage space do I need?
420 BackupPC uses hardlinks to pool files common to different backups.
421 Therefore BackupPC's data store (__TOPDIR__) must point to a single
422 file system that supports hardlinks. You cannot split this file
423 system with multiple mount points or using symbolic links to point a
424 sub-directory to a different file system (it is ok to use a single
425 symbolic link at the top-level directory (__TOPDIR__) to point the
426 entire data store somewhere else). You can of course use any kind of
427 RAID system or logical volume manager that combines the capacity of
428 multiple disks into a single, larger, file system. Such approaches
429 have the advantage that the file system can be expanded without having
432 Any standard linux or unix file system supports hardlinks. NFS mounted
433 file systems work too (provided the underlying file system supports
434 hardlinks). But windows based FAT and NTFS file systems will not work.
436 Starting with BackupPC 3.1.0, run-time checks are done at startup and
437 at the start of each backup to ensure that the file system can support
438 hardlinks, since this is a common area of configuration problems.
440 =head2 How much disk space do I need?
442 Here's one real example for an environment that is backing up 65 laptops
443 with compression off. Each full backup averages 3.2GB. Each incremental
444 backup averages about 0.2GB. Storing one full backup and two incremental
445 backups per laptop is around 240GB of raw data. But because of the
446 pooling of identical files, only 87GB is used. This is without
449 Another example, with compression on: backing up 95 laptops, where
450 each backup averages 3.6GB and each incremental averages about 0.3GB.
451 Keeping three weekly full backups, and six incrementals is around
452 1200GB of raw data. Because of pooling and compression, only 150GB
455 Here's a rule of thumb. Add up the disk usage of all the machines you
456 want to backup (210GB in the first example above). This is a rough
457 minimum space estimate that should allow a couple of full backups and at
458 least half a dozen incremental backups per machine. If compression is on
459 you can reduce the storage requirements by maybe 30-40%. Add some margin
460 in case you add more machines or decide to keep more old backups.
462 Your actual mileage will depend upon the types of clients, operating
463 systems and applications you have. The more uniform the clients and
464 applications the bigger the benefit from pooling common files.
466 For example, the Eudora email tool stores each mail folder in a separate
467 file, and attachments are extracted as separate files. So in the sadly
468 common case of a large attachment emailed to many recipients, Eudora
469 will extract the attachment into a new file. When these machines are
470 backed up, only one copy of the file will be stored on the server, even
471 though the file appears in many different full or incremental backups. In
472 this sense Eudora is a "friendly" application from the point of view of
473 backup storage requirements.
475 An example at the other end of the spectrum is Outlook. Everything
476 (email bodies, attachments, calendar, contact lists) is stored in a
477 single file, which often becomes huge. Any change to this file requires
478 a separate copy of the file to be saved during backup. Outlook is even
479 more troublesome, since it keeps this file locked all the time, so it
480 cannot be read by smbclient whenever Outlook is running. See the
481 L<Limitations|limitations> section for more discussion of this problem.
483 In addition to total disk space, you shold make sure you have
484 plenty of inodes on your BackupPC data partition. Some users have
485 reported running out of inodes on their BackupPC data partition.
486 So even if you have plenty of disk space, BackupPC will report
487 failures when the inodes are exhausted. This is a particular
488 problem with ext2/ext3 file systems that have a fixed number of
489 inodes when the file system is built. Use "df -i" to see your
492 =head2 Step 1: Getting BackupPC
494 Some linux distributions now include BackupPC. The Debian
495 distribution, supprted by Ludovic Drolez, can be found at
496 L<http://packages.debian.org/backuppc>; it should be included
497 in the next stable Debian release. On Debian, BackupPC can
498 be installed with the command:
500 apt-get install backuppc
502 In the future there might be packages for Gentoo and other
503 linux flavors. If the packaged version is older than the
504 released version then you will probably want to install the
505 latest version as described below.
507 Otherwise, manually fetching and installing BackupPC is easy.
508 Start by downloading the latest version from
509 L<http://backuppc.sourceforge.net>. Hit the "Code" button,
510 then select the "backuppc" or "backuppc-beta" package and
511 download the latest version.
513 =head2 Step 2: Installing the distribution
515 First off, there are three perl modules you should install.
516 These are all optional, but highly recommended:
522 To enable compression, you will need to install Compress::Zlib
523 from L<http://www.cpan.org>.
524 You can run "perldoc Compress::Zlib" to see if this module is installed.
528 To support restore via Zip archives you will need to install
529 Archive::Zip, also from L<http://www.cpan.org>.
530 You can run "perldoc Archive::Zip" to see if this module is installed.
534 To support the RSS feature you will need to install XML::RSS, also from
535 L<http://www.cpan.org>. There is not need to install this module if you
536 don't plan on using RSS. You can run "perldoc XML::RSS" to see if this
541 To use rsync and rsyncd with BackupPC you will need to install File::RsyncP.
542 You can run "perldoc File::RsyncP" to see if this module is installed.
543 File::RsyncP is available from L<http://perlrsync.sourceforge.net>.
544 Version 0.52 or later is required.
548 To build and install these packages, fetch the tar.gz file and
549 then run these commands:
551 tar zxvf Archive-Zip-1.16.tar.gz
558 The same sequence of commands can be used for each module.
560 Now let's move onto BackupPC itself. After fetching
561 BackupPC-__VERSION__.tar.gz, run these commands as root:
563 tar zxf BackupPC-__VERSION__.tar.gz
564 cd BackupPC-__VERSION__
567 In the future this release might also have patches available on the
568 SourceForge site. These patch files are text files, with a name of
571 BackupPC-__VERSION__plN.diff
573 where N is the patch level, eg: pl2 is patch-level 2. These
574 patch files are cumulative: you only need apply the last patch
575 file, not all the earlier patch files. If a patch file is
576 available, eg: BackupPC-__VERSION__pl2.diff, you should apply
577 the patch after extracting the tar file:
579 # fetch BackupPC-__VERSION__.tar.gz
580 # fetch BackupPC-__VERSION__pl2.diff
581 tar zxf BackupPC-__VERSION__.tar.gz
582 cd BackupPC-__VERSION__
583 patch -p0 < ../BackupPC-__VERSION__pl2.diff
586 A patch file includes comments that describe that bug fixes
587 and changes. Feel free to review it before you apply the patch.
589 The configure.pl script also accepts command-line options if you
590 wish to run it in a non-interactive manner. It has self-contained
591 documentation for all the command-line options, which you can
596 Starting with BackupPC 3.0.0, the configure.pl script by default
597 complies with the file system hierarchy conventions. The major
598 difference compared to earlier versions is that by default
599 configuration files will be stored in /etc/BackupPC
600 rather than below the data directory, __TOPDIR__/conf,
601 and the log files will be stored in /var/log/BackupPC.
602 rather than below the data directory, __TOPDIR__/log.
604 If you are upgrading from an earlier version the configure.pl script
605 will keep the configuration files and log files in their original
608 When you run configure.pl you will be prompted for the full paths
609 of various executables, and you will be prompted for the following
616 It is best if BackupPC runs as a special user, eg backuppc, that has
617 limited privileges. It is preferred that backuppc belongs to a system
618 administrator group so that sys admin members can browse backuppc files,
619 edit the configuration files and so on. Although configurable, the
620 default settings leave group read permission on pool files, so make
621 sure the BackupPC user's group is chosen restrictively.
623 On this installation, this is __BACKUPPCUSER__.
625 For security purposes you might choose to configure the BackupPC
626 user with the shell set to /bin/false. Since you might need to
627 run some BackupPC programs as the BackupPC user for testing
628 purposes, you can use the -s option to su to explicitly run
631 su -s /bin/bash __BACKUPPCUSER__
633 Depending upon your configuration you might also need the -l option.
637 You need to decide where to put the data directory, below which
638 all the BackupPC data is stored. This needs to be a big file system.
640 On this installation, this is __TOPDIR__.
642 =item Install Directory
644 You should decide where the BackupPC scripts, libraries and documentation
645 should be installed, eg: /usr/local/BackupPC.
647 On this installation, this is __INSTALLDIR__.
649 =item CGI bin Directory
651 You should decide where the BackupPC CGI script resides. This will
652 usually be below Apache's cgi-bin directory.
654 On this installation, this is __CGIDIR__.
656 =item Apache image directory
658 A directory where BackupPC's images are stored so that Apache can
659 serve them. This should be somewhere under Apache's DocumentRoot
662 =item Config and Log directories
664 In this installation the configuration and log directories are
665 located in the following locations:
667 __CONFDIR__/config.pl main config file
668 __CONFDIR__/hosts hosts file
669 __CONFDIR__/pc/HOST.pl per-pc config file
670 __LOGDIR__/BackupPC log files, pid, status
672 The configure.pl script doesn't prompt for these locations but
673 they can be set for new installations using command-line options.
677 =head2 Step 3: Setting up config.pl
679 After running configure.pl, browse through the config file,
680 __CONFDIR__/config.pl, and make sure all the default settings
681 are correct. In particular, you will need to decide whether to use
682 smb, tar or rsync transport (or whether to set it on a per-PC basis)
683 and set the relevant parameters for that transport method.
684 See the section L<Client Setup|step 5: client setup> for more details.
686 =head2 Step 4: Setting up the hosts file
688 The file __CONFDIR__/hosts contains the list of clients to backup.
689 BackupPC reads this file in three cases:
699 When BackupPC is sent a HUP (-1) signal. Assuming you installed the
700 init.d script, you can also do this with "/etc/init.d/backuppc reload".
704 When the modification time of the hosts file changes. BackupPC
705 checks the modification time once during each regular wakeup.
709 Whenever you change the hosts file (to add or remove a host) you can
710 either do a kill -HUP BackupPC_pid or simply wait until the next regular
713 Each line in the hosts file contains three fields, separated
720 This is typically the host name or NetBios name of the client machine
721 and should be in lower case. The host name can contain spaces (escape
722 with a backslash), but it is not recommended.
724 Please read the section L<How BackupPC Finds Hosts|how backuppc finds hosts>.
726 In certain cases you might want several distinct clients to refer
727 to the same physical machine. For example, you might have a database
728 you want to backup, and you want to bracket the backup of the database
729 with shutdown/restart using $Conf{DumpPreUserCmd} and $Conf{DumpPostUserCmd}.
730 But you also want to backup the rest of the machine while the database
731 is still running. In the case you can specify two different clients in
732 the host file, using any mnemonic name (eg: myhost_mysql and myhost), and
733 use $Conf{ClientNameAlias} in myhost_mysql's config.pl to specify the
734 real host name of the machine.
738 Starting with v2.0.0 the way hosts are discovered has changed and now
739 in most cases you should specify 0 for the DHCP flag, even if the host
740 has a dynamically assigned IP address.
741 Please read the section L<How BackupPC Finds Hosts|how backuppc finds hosts>
742 to understand whether you need to set the DHCP flag.
744 You only need to set DHCP to 1 if your client machine doesn't
745 respond to the NetBios multicast request:
749 but does respond to a request directed to its IP address:
753 If you do set DHCP to 1 on any client you will need to specify the range of
754 DHCP addresses to search is specified in $Conf{DHCPAddressRanges}.
756 Note also that the $Conf{ClientNameAlias} feature does not work for
757 clients with DHCP set to 1.
761 This should be the unix login/email name of the user who "owns" or uses
762 this machine. This is the user who will be sent email about this
763 machine, and this user will have permission to stop/start/browse/restore
764 backups for this host. Leave this blank if no specific person should
765 receive email or be allowed to stop/start/browse/restore backups
766 for this host. Administrators will still have full permissions.
770 Additional user names, separate by commas and with no white space,
771 can be specified. These users will also have full permission in
772 the CGI interface to stop/start/browse/restore backups for this host.
773 These users will not be sent email about this host.
777 The first non-comment line of the hosts file is special: it contains
778 the names of the columns and should not be edited.
780 Here's a simple example of a hosts file:
782 host dhcp user moreUsers
783 farside 0 craig jim,dave
786 =head2 Step 5: Client Setup
788 Three methods for getting backup data from a client are supported: smb,
789 tar and rsync. Smb or rsync are the preferred methods for WinXX clients
790 and rsync or tar are the preferred methods for linux/unix/MacOSX clients.
792 The transfer method is set using the $Conf{XferMethod} configuration
793 setting. If you have a mixed environment (ie: you will use smb for some
794 clients and tar for others), you will need to pick the most common
795 choice for $Conf{XferMethod} for the main config.pl file, and then
796 override it in the per-PC config file for those hosts that will use
797 the other method. (Or you could run two completely separate instances
798 of BackupPC, with different data directories, one for WinXX and the
799 other for linux/unix, but then common files between the different
800 machine types will duplicated.)
802 Here are some brief client setup notes:
808 One setup for WinXX clients is to set $Conf{XferMethod} to "smb".
809 Actually, rsyncd is the better method for WinXX if you are prepared to
810 run rsync/cygwin on your WinXX client.
812 If you want to use rsyncd for WinXX clients you can find a pre-packaged
813 zip file on L<http://backuppc.sourceforge.net>. The package is called
814 cygwin-rsync. It contains rsync.exe, template setup files and the
815 minimal set of cygwin libraries for everything to run. The README file
816 contains instructions for running rsync as a service, so it starts
817 automatically everytime you boot your machine. If you use rsync
818 to backup WinXX machines, be sure to set $Conf{ClientCharset}
819 correctly (eg: 'cp1252') so that the WinXX file name encoding is
820 correctly converted to utf8.
822 Otherwise, to use SMB, you can either create shares for the data you want
823 to backup or your can use the existing C$ share. To create a new
824 share, open "My Computer", right click on the drive (eg: C), and
825 select "Sharing..." (or select "Properties" and select the "Sharing"
826 tab). In this dialog box you can enable sharing, select the share name
829 All Windows NT based OS (NT, 2000, XP Pro), are configured by default
830 to share the entire C drive as C$. This is a special share used for
831 various administration functions, one of which is to grant access to backup
832 operators. All you need to do is create a new domain user, specifically
833 for backup. Then add the new backup user to the built in "Backup
834 Operators" group. You now have backup capability for any directory on
835 any computer in the domain in one easy step. This avoids using
836 administrator accounts and only grants permission to do exactly what you
837 want for the given user, i.e.: backup.
838 Also, for additional security, you may wish to deny the ability for this
839 user to logon to computers in the default domain policy.
841 If this machine uses DHCP you will also need to make sure the
842 NetBios name is set. Go to Control Panel|System|Network Identification
843 (on Win2K) or Control Panel|System|Computer Name (on WinXP).
844 Also, you should go to Control Panel|Network Connections|Local Area
845 Connection|Properties|Internet Protocol (TCP/IP)|Properties|Advanced|WINS
846 and verify that NetBios is not disabled.
848 The relevant configuration settings are $Conf{SmbShareName},
849 $Conf{SmbShareUserName}, $Conf{SmbSharePasswd}, $Conf{SmbClientPath},
850 $Conf{SmbClientFullCmd}, $Conf{SmbClientIncrCmd} and
851 $Conf{SmbClientRestoreCmd}.
853 BackupPC needs to know the smb share user name and password for a
854 client machine that uses smb. The user name is specified in
855 $Conf{SmbShareUserName}. There are four ways to tell BackupPC the
862 As an environment variable BPC_SMB_PASSWD set before BackupPC starts.
863 If you start BackupPC manually the BPC_SMB_PASSWD variable must be set
864 manually first. For backward compatibility for v1.5.0 and prior, the
865 environment variable PASSWD can be used if BPC_SMB_PASSWD is not set.
866 Warning: on some systems it is possible to see environment variables of
871 Alternatively the BPC_SMB_PASSWD setting can be included in
872 /etc/init.d/backuppc, in which case you must make sure this file
873 is not world (other) readable.
877 As a configuration variable $Conf{SmbSharePasswd} in
878 __CONFDIR__/config.pl. If you put the password
879 here you must make sure this file is not world (other) readable.
883 As a configuration variable $Conf{SmbSharePasswd} in the per-PC
884 configuration file (__CONFDIR__/pc/$host.pl or
885 __TOPDIR__/pc/$host/config.pl in non-FHS versions of BackupPC).
886 You will have to use this option if the smb share password is different
887 for each host. If you put the password here you must make sure this file
888 is not world (other) readable.
892 Placement and protection of the smb share password is a possible
893 security risk, so please double-check the file and directory
894 permissions. In a future version there might be support for
895 encryption of this password, but a private key will still have to
896 be stored in a protected place. Suggestions are welcome.
898 As an alternative to setting $Conf{XferMethod} to "smb" (using
899 smbclient) for WinXX clients, you can use an smb network filesystem (eg:
900 ksmbfs or similar) on your linux/unix server to mount the share,
901 and then set $Conf{XferMethod} to "tar" (use tar on the network
902 mounted file system).
904 Also, to make sure that file names with special characters are correctly
905 transferred by smbclient you should make sure that the smb.conf file
911 UTF8 is the default setting, so if the parameter is missing then it
912 is ok. With this setting $Conf{ClientCharset} should be emtpy,
913 since smbclient has already converted the file names to utf8.
917 The preferred setup for linux/unix clients is to set $Conf{XferMethod}
918 to "rsync", "rsyncd" or "tar".
920 You can use either rsync, smb, or tar for linux/unix machines. Smb requires
921 that the Samba server (smbd) be run to provide the shares. Since the smb
922 protocol can't represent special files like symbolic links and fifos,
923 tar and rsync are the better transport methods for linux/unix machines.
924 (In fact, by default samba makes symbolic links look like the file or
925 directory that they point to, so you could get an infinite loop if a
926 symbolic link points to the current or parent directory. If you really
927 need to use Samba shares for linux/unix backups you should turn off the
928 "follow symlinks" samba config setting. See the smb.conf manual page.)
930 The requirements for each Xfer Method are:
936 You must have GNU tar on the client machine. Use "tar --version"
937 or "gtar --version" to verify. The version should be at least
938 1.13.7, and 1.13.20 or greater is recommended. Tar is run on
939 the client machine via rsh or ssh.
941 The relevant configuration settings are $Conf{TarClientPath},
942 $Conf{TarShareName}, $Conf{TarClientCmd}, $Conf{TarFullArgs},
943 $Conf{TarIncrArgs}, and $Conf{TarClientRestoreCmd}.
947 You should have at least rsync 2.6.3, and the latest version is
948 recommended. Rsync is run on the remote client via rsh or ssh.
950 The relevant configuration settings are $Conf{RsyncClientPath},
951 $Conf{RsyncClientCmd}, $Conf{RsyncClientRestoreCmd}, $Conf{RsyncShareName},
952 $Conf{RsyncArgs}, and $Conf{RsyncRestoreArgs}.
956 You should have at least rsync 2.6.3, and the latest version is
957 recommended. In this case the rsync daemon should be running on
958 the client machine and BackupPC connects directly to it.
960 The relevant configuration settings are $Conf{RsyncdClientPort},
961 $Conf{RsyncdUserName}, $Conf{RsyncdPasswd}, $Conf{RsyncdAuthRequired},
962 $Conf{RsyncShareName}, $Conf{RsyncArgs}, and $Conf{RsyncRestoreArgs}.
963 $Conf{RsyncShareName} is the name of an rsync module (ie: the thing
964 in square brackets in rsyncd's conf file -- see rsyncd.conf), not a
967 Be aware that rsyncd will remove the leading '/' from path names in
968 symbolic links if you specify "use chroot = no" in the rsynd.conf file.
969 See the rsyncd.conf manual page for more information.
973 You need to set $Conf{ClientCharset} to the client's charset so that
974 file names are correctly converted to utf8. Use "locale charmap"
975 on the client to see its charset.
977 For linux/unix machines you should not backup "/proc". This directory
978 contains a variety of files that look like regular files but they are
979 special files that don't need to be backed up (eg: /proc/kcore is a
980 regular file that contains physical memory). See $Conf{BackupFilesExclude}.
981 It is safe to back up /dev since it contains mostly character-special
982 and block-special files, which are correctly handed by BackupPC
983 (eg: backing up /dev/hda5 just saves the block-special file information,
984 not the contents of the disk).
986 Alternatively, rather than backup all the file systems as a single
987 share ("/"), it is easier to restore a single file system if you backup
988 each file system separately. To do this you should list each file system
989 mount point in $Conf{TarShareName} or $Conf{RsyncShareName}, and add the
990 --one-file-system option to $Conf{TarClientCmd} or $Conf{RsyncArgs}.
991 In this case there is no need to exclude /proc explicitly since it looks
992 like a different file system.
994 Next you should decide whether to run tar over ssh, rsh or nfs. Ssh is
995 the preferred method. Rsh is not secure and therefore not recommended.
996 Nfs will work, but you need to make sure that the BackupPC user (running
997 on the server) has sufficient permissions to read all the files below
1000 Ssh allows BackupPC to run as a privileged user on the client (eg:
1001 root), since it needs sufficient permissions to read all the backup
1002 files. Ssh is setup so that BackupPC on the server (an otherwise low
1003 privileged user) can ssh as root on the client, without being prompted
1004 for a password. There are two common versions of ssh: v1 and v2. Here
1005 are some instructions for one way to setup ssh. (Check which version
1006 of SSH you have by typing "ssh" or "man ssh".)
1010 In general this should be similar to Linux/Unix machines.
1011 In versions 10.4 and later, the native MacOSX tar works,
1012 and also supports resource forks. xtar is another option,
1013 and rsync works too (although the MacOSX-supplied rsync
1014 has an extension for extended attributes that is not
1015 compatible with standard rsync).
1019 SSH is a secure way to run tar or rsync on a backup client to extract
1020 the data. SSH provides strong authentication and encryption of
1023 Note that if you run rsyncd (rsync daemon), ssh is not used.
1024 In this case, rsyncd provides its own authentication, but there
1025 is no encryption of network data. If you want encryption of
1026 network data you can use ssh to create a tunnel, or use a
1027 program like stunnel. If someone submits instructions I
1029 Setup instructions for ssh are at
1030 L<http://backuppc.sourceforge.net/faq/ssh.html>.
1032 =item Clients that use DHCP
1034 If a client machine uses DHCP BackupPC needs some way to find the
1035 IP address given the host name. One alternative is to set dhcp
1036 to 1 in the hosts file, and BackupPC will search a pool of IP
1037 addresses looking for hosts. More efficiently, it is better to
1038 set dhcp = 0 and provide a mechanism for BackupPC to find the
1039 IP address given the host name.
1041 For WinXX machines BackupPC uses the NetBios name server to determine
1042 the IP address given the host name.
1043 For unix machines you can run nmbd (the NetBios name server) from
1044 the Samba distribution so that the machine responds to a NetBios
1045 name request. See the manual page and Samba documentation for more
1048 Alternatively, you can set $Conf{NmbLookupFindHostCmd} to any command
1049 that returns the IP address given the host name.
1051 Please read the section L<How BackupPC Finds Hosts|how backuppc finds hosts>
1056 =head2 Step 6: Running BackupPC
1058 The installation contains an init.d backuppc script that can be copied
1059 to /etc/init.d so that BackupPC can auto-start on boot.
1060 See init.d/README for further instructions.
1062 BackupPC should be ready to start. If you installed the init.d script,
1063 then you should be able to run BackupPC with:
1065 /etc/init.d/backuppc start
1067 (This script can also be invoked with "stop" to stop BackupPC and "reload"
1068 to tell BackupPC to reload config.pl and the hosts file.)
1072 __INSTALLDIR__/bin/BackupPC -d
1074 as user __BACKUPPCUSER__. The -d option tells BackupPC to run as a daemon
1075 (ie: it does an additional fork).
1077 Any immediate errors will be printed to stderr and BackupPC will quit.
1078 Otherwise, look in __LOGDIR__/LOG and verify that BackupPC reports
1079 it has started and all is ok.
1081 =head2 Step 7: Talking to BackupPC
1083 You should verify that BackupPC is running by using BackupPC_serverMesg.
1084 This sends a message to BackupPC via the unix (or TCP) socket and prints
1085 the response. Like all BackupPC programs, BackupPC_serverMesg
1086 should be run as the BackupPC user (__BACKUPPCUSER__), so you
1091 before running BackupPC_serverMesg. If the BackupPC user is
1092 configured with /bin/false as the shell, you can use the -s
1093 option to su to explicitly run a shell, eg:
1095 su -s /bin/bash __BACKUPPCUSER__
1097 Depending upon your configuration you might also need
1100 You can request status information and start and stop backups using this
1101 interface. This socket interface is mainly provided for the CGI interface
1102 (and some of the BackupPC sub-programs use it too). But right now we just
1103 want to make sure BackupPC is happy. Each of these commands should
1104 produce some status output:
1106 __INSTALLDIR__/bin/BackupPC_serverMesg status info
1107 __INSTALLDIR__/bin/BackupPC_serverMesg status jobs
1108 __INSTALLDIR__/bin/BackupPC_serverMesg status hosts
1110 The output should be some hashes printed with Data::Dumper. If it
1111 looks cryptic and confusing, and doesn't look like an error message,
1114 The jobs status should initially show just BackupPC_trashClean.
1115 The hosts status should produce a list of every host you have listed
1116 in __CONFDIR__/hosts as part of a big cryptic output line.
1118 You can also request that all hosts be queued:
1120 __INSTALLDIR__/bin/BackupPC_serverMesg backup all
1122 At this point you should make sure the CGI interface works since
1123 it will be much easier to see what is going on. That's our
1126 =head2 Step 8: Checking email delivery
1128 The script BackupPC_sendEmail sends status and error emails to
1129 the administrator and users. It is usually run each night
1130 by BackupPC_nightly.
1132 To verify that it can run sendmail and deliver email correctly
1133 you should ask it to send a test email to you:
1136 __INSTALLDIR__/bin/BackupPC_sendEmail -u MYNAME@MYDOMAIN.COM
1138 BackupPC_sendEmail also takes a -c option that checks if BackupPC
1139 is running, and it sends an email to $Conf{EMailAdminUserName}
1140 if it is not. That can be used as a keep-alive check by adding
1142 __INSTALLDIR__/bin/BackupPC_sendEmail -c
1144 to __BACKUPPCUSER__'s cron.
1146 The -t option to BackupPC_sendEmail causes it to print the email
1147 message instead of invoking sendmail to deliver the message.
1149 =head2 Step 9: CGI interface
1151 The CGI interface script, BackupPC_Admin, is a powerful and flexible
1152 way to see and control what BackupPC is doing. It is written for an
1153 Apache server. If you don't have Apache, see L<http://www.apache.org>.
1155 There are two options for setting up the CGI interface: standard
1156 mode and using mod_perl. Mod_perl provides much higher performance
1157 (around 15x) and is the best choice if your Apache was built with
1158 mod_perl support. To see if your apache was built with mod_perl
1161 httpd -l | egrep mod_perl
1163 If this prints mod_perl.c then your Apache supports mod_perl.
1165 Using mod_perl with BackupPC_Admin requires a dedicated Apache
1166 to be run as the BackupPC user (__BACKUPPCUSER__). This is
1167 because BackupPC_Admin needs permission to access various files
1168 in BackupPC's data directories. In contrast, the standard
1169 installation (without mod_perl) solves this problem by having
1170 BackupPC_Admin installed as setuid to the BackupPC user, so that
1171 BackupPC_Admin runs as the BackuPC user.
1173 Here are some specifics for each setup:
1177 =item Standard Setup
1179 The CGI interface should have been installed by the configure.pl script
1180 in __CGIDIR__/BackupPC_Admin. BackupPC_Admin should have been installed
1181 as setuid to the BackupPC user (__BACKUPPCUSER__), in addition to user
1182 and group execute permission.
1184 You should be very careful about permissions on BackupPC_Admin and
1185 the directory __CGIDIR__: it is important that normal users cannot
1186 directly execute or change BackupPC_Admin, otherwise they can access
1187 backup files for any PC. You might need to change the group ownership
1188 of BackupPC_Admin to a group that Apache belongs to so that Apache
1189 can execute it (don't add "other" execute permission!).
1190 The permissions should look like this:
1192 ls -l __CGIDIR__/BackupPC_Admin
1193 -swxr-x--- 1 __BACKUPPCUSER__ web 82406 Jun 17 22:58 __CGIDIR__/BackupPC_Admin
1195 The setuid script won't work unless perl on your machine was installed
1196 with setuid emulation. This is likely the problem if you get an error
1197 saying such as "Wrong user: my userid is 25, instead of 150", meaning
1198 the script is running as the httpd user, not the BackupPC user.
1199 This is because setuid scripts are disabled by the kernel in most
1200 flavors of unix and linux.
1202 To see if your perl has setuid emulation, see if there is a program
1203 called sperl5.8.0 (or sperl5.8.2 etc, based on your perl version)
1204 in the place where perl is installed. If you can't find this program,
1205 then you have two options: rebuild and reinstall perl with the setuid
1206 emulation turned on (answer "y" to the question "Do you want to do
1207 setuid/setgid emulation?" when you run perl's configure script), or
1208 switch to the mod_perl alternative for the CGI script (which doesn't
1209 need setuid to work).
1211 =item Mod_perl Setup
1213 The advantage of the mod_perl setup is that no setuid script is needed,
1214 and there is a huge performance advantage. Not only does all the perl
1215 code need to be parsed just once, the config.pl and hosts files, plus
1216 the connection to the BackupPC server are cached between requests. The
1217 typical speedup is around 15 times.
1219 To use mod_perl you need to run Apache as user __BACKUPPCUSER__.
1220 If you need to run multiple Apache's for different services then
1221 you need to create multiple top-level Apache directories, each
1222 with their own config file. You can make copies of /etc/init.d/httpd
1223 and use the -d option to httpd to point each http to a different
1224 top-level directory. Or you can use the -f option to explicitly
1225 point to the config file. Multiple Apache's will run on different
1226 Ports (eg: 80 is standard, 8080 is a typical alternative port accessed
1227 via http://yourhost.com:8080).
1229 Inside BackupPC's Apache http.conf file you should check the
1230 settings for ServerRoot, DocumentRoot, User, Group, and Port. See
1231 L<http://httpd.apache.org/docs/server-wide.html> for more details.
1233 For mod_perl, BackupPC_Admin should not have setuid permission, so
1234 you should turn it off:
1236 chmod u-s __CGIDIR__/BackupPC_Admin
1238 To tell Apache to use mod_perl to execute BackupPC_Admin, add this
1239 to Apache's 1.x httpd.conf file:
1241 <IfModule mod_perl.c>
1242 PerlModule Apache::Registry
1244 <Location /cgi-bin/BackupPC/BackupPC_Admin> # <--- change path as needed
1245 SetHandler perl-script
1246 PerlHandler Apache::Registry
1252 Apache 2.0.44 with Perl 5.8.0 on RedHat 7.1, Don Silvia reports that
1253 this works (with tweaks from Michael Tuzi):
1255 LoadModule perl_module modules/mod_perl.so
1258 <Directory /path/to/cgi/>
1259 SetHandler perl-script
1260 PerlResponseHandler ModPerl::Registry
1261 PerlOptions +ParseHeaders
1265 Allow from 192.168.0
1266 AuthName "Backup Admin"
1268 AuthUserFile /path/to/user_file
1272 There are other optimizations and options with mod_perl. For
1273 example, you can tell mod_perl to preload various perl modules,
1274 which saves memory compared to loading separate copies in every
1275 Apache process after they are forked. See Stas's definitive
1276 mod_perl guide at L<http://perl.apache.org/guide>.
1280 BackupPC_Admin requires that users are authenticated by Apache.
1281 Specifically, it expects that Apache sets the REMOTE_USER environment
1282 variable when it runs. There are several ways to do this. One way
1283 is to create a .htaccess file in the cgi-bin directory that looks like:
1285 AuthGroupFile /etc/httpd/conf/group # <--- change path as needed
1286 AuthUserFile /etc/http/conf/passwd # <--- change path as needed
1291 You will also need "AllowOverride Indexes AuthConfig" in the Apache
1292 httpd.conf file to enable the .htaccess file. Alternatively, everything
1293 can go in the Apache httpd.conf file inside a Location directive. The
1294 list of users and password file above can be extracted from the NIS
1297 One alternative is to use LDAP. In Apache's http.conf add these lines:
1299 LoadModule auth_ldap_module modules/auth_ldap.so
1300 AddModule auth_ldap.c
1302 # cgi-bin - auth via LDAP (for BackupPC)
1303 <Location /cgi-binBackupPC/BackupPC_Admin> # <--- change path as needed
1305 AuthName "BackupPC login"
1306 # replace MYDOMAIN, PORT, ORG and CO as needed
1307 AuthLDAPURL ldap://ldap.MYDOMAIN.com:PORT/o=ORG,c=CO?uid?sub?(objectClass=*)
1311 If you want to disable the user authentication you can set
1312 $Conf{CgiAdminUsers} to '*', which allows any user to have
1313 full access to all hosts and backups. In this case the REMOTE_USER
1314 environment variable does not have to be set by Apache.
1316 Alternatively, you can force a particular user name by getting Apache
1317 to set REMOTE_USER, eg, to hardcode the user to www you could add
1318 this to Apache's httpd.conf:
1320 <Location /cgi-bin/BackupPC/BackupPC_Admin> # <--- change path as needed
1321 Setenv REMOTE_USER www
1324 Finally, you should also edit the config.pl file and adjust, as necessary,
1325 the CGI-specific settings. They're near the end of the config file. In
1326 particular, you should specify which users or groups have administrator
1327 (privileged) access: see the config settings $Conf{CgiAdminUserGroup}
1328 and $Conf{CgiAdminUsers}. Also, the configure.pl script placed various
1329 images into $Conf{CgiImageDir} that BackupPC_Admin needs to serve
1330 up. You should make sure that $Conf{CgiImageDirURL} is the correct
1331 URL for the image directory.
1333 See the section L<Fixing installation problems|fixing installation problems> for suggestions on debugging the Apache authentication setup.
1335 =head2 How BackupPC Finds Hosts
1337 Starting with v2.0.0 the way hosts are discovered has changed. In most
1338 cases you should specify 0 for the DHCP flag in the conf/hosts file,
1339 even if the host has a dynamically assigned IP address.
1341 BackupPC (starting with v2.0.0) looks up hosts with DHCP = 0 in this manner:
1347 First DNS is used to lookup the IP address given the client's name
1348 using perl's gethostbyname() function. This should succeed for machines
1349 that have fixed IP addresses that are known via DNS. You can manually
1350 see whether a given host have a DNS entry according to perls'
1351 gethostbyname function with this command:
1353 perl -e 'print(gethostbyname("myhost") ? "ok\n" : "not found\n");'
1357 If gethostbyname() fails, BackupPC then attempts a NetBios multicast to
1358 find the host. Provided your client machine is configured properly,
1359 it should respond to this NetBios multicast request. Specifically,
1360 BackupPC runs a command of this form:
1364 If this fails you will see output like:
1366 querying myhost on 10.10.255.255
1367 name_query failed to find name myhost
1369 If this success you will see output like:
1371 querying myhost on 10.10.255.255
1372 10.10.1.73 myhost<00>
1374 Depending on your netmask you might need to specify the -B option to
1375 nmblookup. For example:
1377 nmblookup -B 10.10.1.255 myhost
1379 If necessary, experiment on the nmblookup command that will return the
1380 IP address of the client given its name. Then update
1381 $Conf{NmbLookupFindHostCmd} with any necessary options to nmblookup.
1385 For hosts that have the DHCP flag set to 1, these machines are
1386 discovered as follows:
1392 A DHCP address pool ($Conf{DHCPAddressRanges}) needs to be specified.
1393 BackupPC will check the NetBIOS name of each machine in the range using
1394 a command of the form:
1396 nmblookup -A W.X.Y.Z
1398 where W.X.Y.Z is each candidate address from $Conf{DHCPAddressRanges}.
1399 Any host that has a valid NetBIOS name returned by this command (ie:
1400 matching an entry in the hosts file) will be backed up. You can
1401 modify the specific nmblookup command if necessary via $Conf{NmbLookupCmd}.
1405 You only need to use this DHCP feature if your client machine doesn't
1406 respond to the NetBios multicast request:
1410 but does respond to a request directed to its IP address:
1412 nmblookup -A W.X.Y.Z
1416 =head2 Other installation topics
1420 =item Removing a client
1422 If there is a machine that no longer needs to be backed up (eg: a retired
1423 machine) you have two choices. First, you can keep the backups accessible
1424 and browsable, but disable all new backups. Alternatively, you can
1425 completely remove the client and all its backups.
1427 To disable backups for a client there are two special values for
1428 $Conf{FullPeriod} in that client's per-PC config.pl file:
1434 Don't do any regular backups on this machine. Manually
1435 requested backups (via the CGI interface) will still occur.
1439 Don't do any backups on this machine. Manually requested
1440 backups (via the CGI interface) will be ignored.
1444 This will still allow that client's old backups to be browsable
1447 To completely remove a client and all its backups, you should remove its
1448 entry in the conf/hosts file, and then delete the __TOPDIR__/pc/$host
1449 directory. Whenever you change the hosts file, you should send
1450 BackupPC a HUP (-1) signal so that it re-reads the hosts file.
1451 If you don't do this, BackupPC will automatically re-read the
1452 hosts file at the next regular wakeup.
1454 Note that when you remove a client's backups you won't initially recover
1455 a lot of disk space. That's because the client's files are still in
1456 the pool. Overnight, when BackupPC_nightly next runs, all the unused
1457 pool files will be deleted and this will recover the disk space used
1458 by the client's backups.
1460 =item Copying the pool
1462 If the pool disk requirements grow you might need to copy the entire
1463 data directory to a new (bigger) file system. Hopefully you are lucky
1464 enough to avoid this by having the data directory on a RAID file system
1465 or LVM that allows the capacity to be grown in place by adding disks.
1467 The backup data directories contain large numbers of hardlinks. If
1468 you try to copy the pool the target directory will occupy a lot more
1469 space if the hardlinks aren't re-established.
1471 The best way to copy a pool file system, if possible, is by copying
1472 the raw device at the block level (eg: using dd). Application level
1473 programs that understand hardlinks include the GNU cp program with
1474 the -a option and rsync -H. However, the large number of hardlinks
1475 in the pool will make the memory usage large and the copy very slow.
1476 Don't forget to stop BackupPC while the copy runs.
1478 Starting in 3.0.0 a new script bin/BackupPC_tarPCCopy can be
1479 used to assist the copy process. Given one or more pc paths
1480 (eg: TOPDIR/pc/HOST or TOPDIR/pc/HOST/nnn), BackupPC_tarPCCopy
1481 creates a tar archive with all the hardlinks pointing to ../cpool/....
1482 Any files not hardlinked (eg: backups, LOG etc) are included
1485 You will need to specify the -P option to tar when you extract
1486 the archive generated by BackupPC_tarPCCopy since the hardlink
1487 targets are outside of the directory being extracted.
1489 To copy a complete store (ie: __TOPDIR__) using BackupPC_tarPCCopy
1496 stop BackupPC so that the store is static.
1500 copy the cpool, conf and log directory trees using any technique
1501 (like cp, rsync or tar) wihtout the need to preserve hardlinks.
1505 copy the pc directory using BackupPC_tarPCCopy:
1511 __INSTALLDIR__/bin/BackupPC_tarPCCopy __TOPDIR__/pc | tar xvPf -
1517 =head2 Fixing installation problems
1519 Please see the FAQ at L<http://backuppc.sourceforge.net/faq> for
1520 debugging suggestions.
1522 =head1 Restore functions
1524 BackupPC supports several different methods for restoring files. The
1525 most convenient restore options are provided via the CGI interface.
1526 Alternatively, backup files can be restored using manual commands.
1528 =head2 CGI restore options
1530 By selecting a host in the CGI interface, a list of all the backups
1531 for that machine will be displayed. By selecting the backup number
1532 you can navigate the shares and directory tree for that backup.
1534 BackupPC's CGI interface automatically fills incremental backups
1535 with the corresponding full backup, which means each backup has
1536 a filled appearance. Therefore, there is no need to do multiple
1537 restores from the incremental and full backups: BackupPC does all
1538 the hard work for you. You simply select the files and directories
1539 you want from the correct backup vintage in one step.
1541 You can download a single backup file at any time simply by selecting
1542 it. Your browser should prompt you with the file name and ask you
1543 whether to open the file or save it to disk.
1545 Alternatively, you can select one or more files or directories in
1546 the currently selected directory and select "Restore selected files".
1547 (If you need to restore selected files and directories from several
1548 different parent directories you will need to do that in multiple
1551 If you select all the files in a directory, BackupPC will replace
1552 the list of files with the parent directory. You will be presented
1553 with a screen that has three options:
1557 =item Option 1: Direct Restore
1559 With this option the selected files and directories are restored
1560 directly back onto the host, by default in their original location.
1561 Any old files with the same name will be overwritten, so use caution.
1562 You can optionally change the target host name, target share name,
1563 and target path prefix for the restore, allowing you to restore the
1564 files to a different location.
1566 Once you select "Start Restore" you will be prompted one last time
1567 with a summary of the exact source and target files and directories
1568 before you commit. When you give the final go ahead the restore
1569 operation will be queued like a normal backup job, meaning that it
1570 will be deferred if there is a backup currently running for that host.
1571 When the restore job is run, smbclient, tar, rsync or rsyncd is used
1572 (depending upon $Conf{XferMethod}) to actually restore the files.
1573 Sorry, there is currently no option to cancel a restore that has been
1576 A record of the restore request, including the result and list of
1577 files and directories, is kept. It can be browsed from the host's
1578 home page. $Conf{RestoreInfoKeepCnt} specifies how many old restore
1579 status files to keep.
1581 Note that for direct restore to work, the $Conf{XferMethod} must
1582 be able to write to the client. For example, that means an SMB
1583 share for smbclient needs to be writable, and the rsyncd module
1584 needs "read only" set to "false". This creates additional security
1585 risks. If you only create read-only SMB shares (which is a good
1586 idea), then the direct restore will fail. You can disable the
1587 direct restore option by setting $Conf{SmbClientRestoreCmd},
1588 $Conf{TarClientRestoreCmd} and $Conf{RsyncRestoreArgs} to undef.
1590 =item Option 2: Download Zip archive
1592 With this option a zip file containing the selected files and directories
1593 is downloaded. The zip file can then be unpacked or individual files
1594 extracted as necessary on the host machine. The compression level can be
1595 specified. A value of 0 turns off compression.
1597 When you select "Download Zip File" you should be prompted where to
1598 save the restore.zip file.
1600 BackupPC does not consider downloading a zip file as an actual
1601 restore operation, so the details are not saved for later browsing
1602 as in the first case. However, a mention that a zip file was
1603 downloaded by a particular user, and a list of the files, does
1604 appear in BackupPC's log file.
1606 =item Option 3: Download Tar archive
1608 This is identical to the previous option, except a tar file is downloaded
1609 rather than a zip file (and there is currently no compression option).
1613 =head2 Command-line restore options
1615 Apart from the CGI interface, BackupPC allows you to restore files
1616 and directories from the command line. The following programs can
1623 For each file name argument it inflates (uncompresses) the file and
1624 writes it to stdout. To use BackupPC_zcat you could give it the
1627 __INSTALLDIR__/bin/BackupPC_zcat __TOPDIR__/pc/host/5/fc/fcraig/fexample.txt > example.txt
1629 It's your responsibility to make sure the file is really compressed:
1630 BackupPC_zcat doesn't check which backup the requested file is from.
1631 BackupPC_zcat returns a non-zero status if it fails to uncompress
1634 =item BackupPC_tarCreate
1636 BackupPC_tarCreate creates a tar file for any files or directories in
1637 a particular backup. Merging of incrementals is done automatically,
1638 so you don't need to worry about whether certain files appear in the
1639 incremental or full backup.
1643 BackupPC_tarCreate [options] files/directories...
1645 -h host host from which the tar archive is created
1646 -n dumpNum dump number from which the tar archive is created
1647 A negative number means relative to the end (eg -1
1648 means the most recent dump, -2 2nd most recent etc).
1649 -s shareName share name from which the tar archive is created
1652 -t print summary totals
1653 -r pathRemove path prefix that will be replaced with pathAdd
1654 -p pathAdd new path prefix
1655 -b BLOCKS BLOCKS x 512 bytes per record (default 20; same as tar)
1656 -w writeBufSz write buffer size (default 1048576 = 1MB)
1657 -e charset charset for encoding file names (default: value of
1658 $Conf{ClientCharset} when backup was done)
1659 -l just print a file listing; don't generate an archive
1660 -L just print a detailed file listing; don't generate an archive
1662 The command-line files and directories are relative to the specified
1663 shareName. The tar file is written to stdout.
1665 The -h, -n and -s options specify which dump is used to generate
1666 the tar archive. The -r and -p options can be used to relocate
1667 the paths in the tar archive so extracted files can be placed
1668 in a location different from their original location.
1670 =item BackupPC_zipCreate
1672 BackupPC_zipCreate creates a zip file for any files or directories in
1673 a particular backup. Merging of incrementals is done automatically,
1674 so you don't need to worry about whether certain files appear in the
1675 incremental or full backup.
1679 BackupPC_zipCreate [options] files/directories...
1681 -h host host from which the zip archive is created
1682 -n dumpNum dump number from which the tar archive is created
1683 A negative number means relative to the end (eg -1
1684 means the most recent dump, -2 2nd most recent etc).
1685 -s shareName share name from which the zip archive is created
1688 -t print summary totals
1689 -r pathRemove path prefix that will be replaced with pathAdd
1690 -p pathAdd new path prefix
1691 -c level compression level (default is 0, no compression)
1692 -e charset charset for encoding file names (default: cp1252)
1694 The command-line files and directories are relative to the specified
1695 shareName. The zip file is written to stdout. The -h, -n and -s
1696 options specify which dump is used to generate the zip archive. The
1697 -r and -p options can be used to relocate the paths in the zip archive
1698 so extracted files can be placed in a location different from their
1703 Each of these programs reside in __INSTALLDIR__/bin.
1705 =head1 Archive functions
1707 BackupPC supports archiving to removable media. For users that require
1708 offsite backups, BackupPC can create archives that stream to tape
1709 devices, or create files of specified sizes to fit onto cd or dvd media.
1711 Each archive type is specified by a BackupPC host with its XferMethod
1712 set to 'archive'. This allows for multiple configurations at sites where
1713 there might be a combination of tape and cd/dvd backups being made.
1715 BackupPC provides a menu that allows one or more hosts to be archived.
1716 The most recent backup of each host is archived using BackupPC_tarCreate,
1717 and the output is optionally compressed and split into fixed-sized
1720 The archive for each host is done by default using
1721 __INSTALLDIR__/BackupPC_archiveHost. This script can be copied
1722 and customized as needed.
1724 =head2 Configuring an Archive Host
1726 To create an Archive Host, add it to the hosts file just as any other host
1727 and call it a name that best describes the type of archive, e.g. ArchiveDLT
1729 To tell BackupPC that the Host is for Archives, create a config.pl file in
1730 the Archive Hosts's pc directory, adding the following line:
1732 $Conf{XferMethod} = 'archive';
1734 To further customise the archive's parameters you can adding the changed
1735 parameters in the host's config.pl file. The parameters are explained in
1736 the config.pl file. Parameters may be fixed or the user can be allowed
1737 to change them (eg: output device).
1739 The per-host archive command is $Conf{ArchiveClientCmd}. By default
1742 __INSTALLDIR__/BackupPC_archiveHost
1744 which you can copy and customize as necessary.
1746 =head2 Starting an Archive
1748 In the web interface, click on the Archive Host you wish to use. You will see a
1749 list of previous archives and a summary on each. By clicking the "Start Archive"
1750 button you are presented with the list of hosts and the approximate backup size
1751 (note this is raw size, not projected compressed size) Select the hosts you wish
1752 to archive and press the "Archive Selected Hosts" button.
1754 The next screen allows you to adjust the parameters for this archive run.
1755 Press the "Start the Archive" to start archiving the selected hosts with the
1756 parameters displayed.
1758 =head2 Starting an Archive from the command line
1760 The script BackupPC_archiveStart can be used to start an archive from
1761 the command line (or cron etc). The usage is:
1763 BackupPC_archiveStart archiveHost userName hosts...
1765 This creates an archive of the most recent backup of each of
1766 the specified hosts. The first two arguments are the archive
1767 host and the user name making the request.
1769 =head1 Other CGI Functions
1771 =head2 Configuration and Host Editor
1773 The CGI interface has a complete configuration and host editor.
1774 Only the administrator can edit the main configuration settings
1775 and hosts. The edit links are in the left navigation bar.
1777 When changes are made to any parameter a "Save" button appears
1778 at the top of the page. If you are editing a text box you will
1779 need to click outside of the text box to make the Save button
1780 appear. If you don't select Save then the changes won't be saved.
1782 The host-specific configuration can be edited from the host
1783 summary page using the link in the left navigation bar.
1784 The administrator can edit any of the host-specific
1785 configuration settings.
1787 When editing the host-specific configuration, each parameter has
1788 an "override" setting that denotes the value is host-specific,
1789 meaning that it overrides the setting in the main configuration.
1790 If you unselect "override" then the setting is removed from
1791 the host-specific configuration, and the main configuration
1794 User's can edit their host-specific configuration if enabled
1795 via $Conf{CgiUserConfigEditEnable}. The specific subset
1796 of configuration settings that a user can edit is specified
1797 with $Conf{CgiUserConfigEdit}. It is recommended to make this
1798 list short as possible (you probably don't want your users saving
1799 dozens of backups) and it is essential that they can't edit any
1800 of the Cmd configuration settings, otherwise they can specify
1801 an arbitrary command that will be executed as the BackupPC
1806 BackupPC supports a very basic RSS feed. Provided you have the
1807 XML::RSS perl module installed, a URL simular to this will
1808 provide RSS information:
1810 http://localhost/cgi-bin/BackupPC/BackupPC_Admin?action=rss
1812 This feature is experimental. The information included will
1815 =head1 BackupPC Design
1817 =head2 Some design issues
1821 =item Pooling common files
1823 To quickly see if a file is already in the pool, an MD5 digest of the
1824 file length and contents is used as the file name in the pool. This
1825 can't guarantee a file is identical: it just reduces the search to
1826 often a single file or handful of files. A complete file comparison
1827 is always done to verify if two files are really the same.
1829 Identical files on multiples backups are represented by hard links.
1830 Hardlinks are used so that identical files all refer to the same
1831 physical file on the server's disk. Also, hard links maintain
1832 reference counts so that BackupPC knows when to delete unused files
1835 For the computer-science majors among you, you can think of the pooling
1836 system used by BackupPC as just a chained hash table stored on a (big)
1839 =item The hashing function
1841 There is a tradeoff between how much of file is used for the MD5 digest
1842 and the time taken comparing all the files that have the same hash.
1844 Using the file length and just the first 4096 bytes of the file for the
1845 MD5 digest produces some repetitions. One example: with 900,000 unique
1846 files in the pool, this hash gives about 7,000 repeated files, and in
1847 the worst case 500 files have the same hash. That's not bad: we only
1848 have to do a single file compare 99.2% of the time. But in the worst
1849 case we have to compare as many as 500 files checking for a match.
1851 With a modest increase in CPU time, if we use the file length and the
1852 first 256K of the file we now only have 500 repeated files and in the
1853 worst case around 20 files have the same hash. Furthermore, if we
1854 instead use the first and last 128K of the file (more specifically, the
1855 first and eighth 128K chunks for files larger than 1MB) we get only 300
1856 repeated files and in the worst case around 20 files have the same hash.
1858 Based on this experimentation, this is the hash function used by BackupPC.
1859 It is important that you don't change the hash function after files
1860 are already in the pool. Otherwise your pool will grow to twice the
1861 size until all the old backups (and all the old files with old hashes)
1866 BackupPC supports compression. It uses the deflate and inflate methods
1867 in the Compress::Zlib module, which is based on the zlib compression
1868 library (see L<http://www.gzip.org/zlib/>).
1870 The $Conf{CompressLevel} setting specifies the compression level to use.
1871 Zero (0) means no compression. Compression levels can be from 1 (least
1872 cpu time, slightly worse compression) to 9 (most cpu time, slightly
1873 better compression). The recommended value is 3. Changing it to 5, for
1874 example, will take maybe 20% more cpu time and will get another 2-3%
1875 additional compression. Diminishing returns set in above 5. See the zlib
1876 documentation for more information about compression levels.
1878 BackupPC implements compression with minimal CPU load. Rather than
1879 compressing every incoming backup file and then trying to match it
1880 against the pool, BackupPC computes the MD5 digest based on the
1881 uncompressed file, and matches against the candidate pool files by
1882 comparing each uncompressed pool file against the incoming backup file.
1883 Since inflating a file takes roughly a factor of 10 less CPU time than
1884 deflating there is a big saving in CPU time.
1886 The combination of pooling common files and compression can yield
1887 a factor of 8 or more overall saving in backup storage.
1891 =head2 BackupPC operation
1893 BackupPC reads the configuration information from
1894 __CONFDIR__/config.pl. It then runs and manages all the backup
1895 activity. It maintains queues of pending backup requests, user backup
1896 requests and administrative commands. Based on the configuration various
1897 requests will be executed simultaneously.
1899 As specified by $Conf{WakeupSchedule}, BackupPC wakes up periodically
1900 to queue backups on all the PCs. This is a four step process:
1906 For each host and DHCP address backup requests are queued on the
1907 background command queue.
1911 For each PC, BackupPC_dump is forked. Several of these may be run in
1912 parallel, based on the configuration. First a ping is done to see if
1913 the machine is alive. If this is a DHCP address, nmblookup is run to
1914 get the netbios name, which is used as the host name. If DNS lookup
1915 fails, $Conf{NmbLookupFindHostCmd} is run to find the IP address from
1916 the host name. The file __TOPDIR__/pc/$host/backups is read to decide
1917 whether a full or incremental backup needs to be run. If no backup is
1918 scheduled, or the ping to $host fails, then BackupPC_dump exits.
1920 The backup is done using the specified XferMethod. Either samba's smbclient
1921 or tar over ssh/rsh/nfs piped into BackupPC_tarExtract, or rsync over ssh/rsh
1922 is run, or rsyncd is connected to, with the incoming data
1923 extracted to __TOPDIR__/pc/$host/new. The XferMethod output is put
1924 into __TOPDIR__/pc/$host/XferLOG.
1926 The letter in the XferLOG file shows the type of object, similar to the
1927 first letter of the modes displayed by ls -l:
1931 b -> block special file
1932 c -> character special file
1933 p -> pipe file (fifo)
1934 nothing -> regular file
1942 new for this backup (ie: directory or file not in pool)
1946 found a match in the pool
1950 file is identical to previous backup (contents were
1951 checksummed and verified during full dump).
1955 file skipped in incremental because attributes are the
1956 same (only displayed if $Conf{XferLogLevel} >= 2).
1960 As BackupPC_tarExtract extracts the files from smbclient or tar, or as
1961 rsync runs, it checks each file in the backup to see if it is identical
1962 to an existing file from any previous backup of any PC. It does this
1963 without needed to write the file to disk. If the file matches an
1964 existing file, a hardlink is created to the existing file in the pool.
1965 If the file does not match any existing files, the file is written to
1966 disk and the file name is saved in __TOPDIR__/pc/$host/NewFileList for
1967 later processing by BackupPC_link. BackupPC_tarExtract and rsync can handle
1968 arbitrarily large files and multiple candidate matching files without
1969 needing to write the file to disk in the case of a match. This
1970 significantly reduces disk writes (and also reads, since the pool file
1971 comparison is done disk to memory, rather than disk to disk).
1973 Based on the configuration settings, BackupPC_dump checks each
1974 old backup to see if any should be removed. Any expired backups
1975 are moved to __TOPDIR__/trash for later removal by BackupPC_trashClean.
1979 For each complete, good, backup, BackupPC_link is run.
1980 To avoid race conditions as new files are linked into the
1981 pool area, only a single BackupPC_link program runs
1982 at a time and the rest are queued.
1984 BackupPC_link reads the NewFileList written by BackupPC_dump and
1985 inspects each new file in the backup. It re-checks if there is a
1986 matching file in the pool (another BackupPC_link
1987 could have added the file since BackupPC_dump checked). If so, the file
1988 is removed and replaced by a hard link to the existing file. If the file
1989 is new, a hard link to the file is made in the pool area, so that this
1990 file is available for checking against each new file and new backup.
1992 Then, if $Conf{IncrFill} is set (note that the default setting is
1993 off), for each incremental backup, hard links are made in the new
1994 backup to all files that were not extracted during the incremental
1995 backups. The means the incremental backup looks like a complete
1996 image of the PC (with the exception that files that were removed on
1997 the PC since the last full backup will still appear in the backup
2000 The CGI interface knows how to merge unfilled incremental backups will
2001 the most recent prior filled (full) backup, giving the incremental
2002 backups a filled appearance. The default for $Conf{IncrFill} is off,
2003 since there is no need to fill incremental backups. This saves
2004 some level of disk activity, since lots of extra hardlinks are no
2005 longer needed (and don't have to be deleted when the backup expires).
2009 BackupPC_trashClean is always run in the background to remove any
2010 expired backups. Every 5 minutes it wakes up and removes all the files
2011 in __TOPDIR__/trash.
2013 Also, once each night, BackupPC_nightly is run to complete some
2014 additional administrative tasks, such as cleaning the pool. This
2015 involves removing any files in the pool that only have a single
2016 hard link (meaning no backups are using that file). Again, to
2017 avoid race conditions, BackupPC_nightly is only run when there
2018 are no BackupPC_link processes running. When BackupPC_nightly is
2019 run no new BackupPC_link jobs are started. If BackupPC_nightly
2020 takes too long to run, the settings $Conf{MaxBackupPCNightlyJobs}
2021 and $Conf{BackupPCNightlyPeriod} can be used to run several
2022 BackupPC_nightly processes in parallel, and to split its job over
2027 BackupPC also listens for TCP connections on $Conf{ServerPort}, which
2028 is used by the CGI script BackupPC_Admin for status reporting and
2029 user-initiated backup or backup cancel requests.
2031 =head2 Storage layout
2033 BackupPC resides in several directories:
2037 =item __INSTALLDIR__
2039 Perl scripts comprising BackupPC reside in __INSTALLDIR__/bin,
2040 libraries are in __INSTALLDIR__/lib and documentation
2041 is in __INSTALLDIR__/doc.
2045 The CGI script BackupPC_Admin resides in this cgi binary directory.
2049 All the configuration information resides below __CONFDIR__.
2050 This directory contains:
2052 The directory __CONFDIR__ contains:
2058 Configuration file. See L<Configuration file|configuration file>
2059 below for more details.
2063 Hosts file, which lists all the PCs to backup.
2067 The directory __CONFDIR__/pc contains per-client configuration files
2068 that override settings in the main configuration file. Each file
2069 is named __CONFDIR__/pc/HOST.pl, where HOST is the host name.
2071 In pre-FHS versions of BackupPC these files were located in
2072 __TOPDIR__/pc/HOST/config.pl.
2078 The directory __LOGDIR__ (__TOPDIR__/log on pre-FHS versions
2079 of BackupPC) contains:
2085 Current (today's) log file output from BackupPC.
2087 =item LOG.0 or LOG.0.z
2089 Yesterday's log file output. Log files are aged daily and compressed
2090 (if compression is enabled), and old LOG files are deleted.
2094 Contains BackupPC's process id.
2098 A summary of BackupPC's status written periodically by BackupPC so
2099 that certain state information can be maintained if BackupPC is
2100 restarted. Should not be edited.
2102 =item UserEmailInfo.pl
2104 A summary of what email was last sent to each user, and when the
2105 last email was sent. Should not be edited.
2111 All of BackupPC's data (PC backup images, logs, configuration information)
2112 is stored below this directory.
2116 Below __TOPDIR__ are several directories:
2120 =item __TOPDIR__/trash
2122 Any directories and files below this directory are periodically deleted
2123 whenever BackupPC_trashClean checks. When a backup is aborted or when an
2124 old backup expires, BackupPC_dump simply moves the directory to
2125 __TOPDIR__/trash for later removal by BackupPC_trashClean.
2127 =item __TOPDIR__/pool
2129 All uncompressed files from PC backups are stored below __TOPDIR__/pool.
2130 Each file's name is based on the MD5 hex digest of the file contents.
2131 Specifically, for files less than 256K, the file length and the entire
2132 file is used. For files up to 1MB, the file length and the first and
2133 last 128K are used. Finally, for files longer than 1MB, the file length,
2134 and the first and eighth 128K chunks for the file are used.
2136 Each file is stored in a subdirectory X/Y/Z, where X, Y, Z are the
2137 first 3 hex digits of the MD5 digest.
2139 For example, if a file has an MD5 digest of 123456789abcdef0,
2140 the file is stored in __TOPDIR__/pool/1/2/3/123456789abcdef0.
2142 The MD5 digest might not be unique (especially since not all the file's
2143 contents are used for files bigger than 256K). Different files that have
2144 the same MD5 digest are stored with a trailing suffix "_n" where n is
2145 an incrementing number starting at 0. So, for example, if two additional
2146 files were identical to the first, except the last byte was different,
2147 and assuming the file was larger than 1MB (so the MD5 digests are the
2148 same but the files are actually different), the three files would be
2151 __TOPDIR__/pool/1/2/3/123456789abcdef0
2152 __TOPDIR__/pool/1/2/3/123456789abcdef0_0
2153 __TOPDIR__/pool/1/2/3/123456789abcdef0_1
2155 Both BackupPC_dump (actually, BackupPC_tarExtract) and BackupPC_link are
2156 responsible for checking newly backed up files against the pool. For
2157 each file, the MD5 digest is used to generate a file name in the pool
2158 directory. If the file exists in the pool, the contents are compared.
2159 If there is no match, additional files ending in "_n" are checked.
2160 (Actually, BackupPC_tarExtract compares multiple candidate files in
2161 parallel.) If the file contents exactly match, the file is created by
2162 simply making a hard link to the pool file (this is done by
2163 BackupPC_tarExtract as the backup proceeds). Otherwise,
2164 BackupPC_tarExtract writes the new file to disk and a new hard link is
2165 made in the pool to the file (this is done later by BackupPC_link).
2167 Therefore, every file in the pool will have at least 2 hard links
2168 (one for the pool file and one for the backup file below __TOPDIR__/pc).
2169 Identical files from different backups or PCs will all be linked to
2170 the same file. When old backups are deleted, some files in the pool
2171 might only have one link. BackupPC_nightly checks the entire pool
2172 and removes all files that have only a single link, thereby recovering
2173 the storage for that file.
2175 One other issue: zero length files are not pooled, since there are a lot
2176 of these files and on most file systems it doesn't save any disk space
2177 to turn these files into hard links.
2179 =item __TOPDIR__/cpool
2181 All compressed files from PC backups are stored below __TOPDIR__/cpool.
2182 Its layout is the same as __TOPDIR__/pool, and the hashing function
2183 is the same (and, importantly, based on the uncompressed file, not
2184 the compressed file).
2186 =item __TOPDIR__/pc/$host
2188 For each PC $host, all the backups for that PC are stored below
2189 the directory __TOPDIR__/pc/$host. This directory contains the
2196 Current log file for this PC from BackupPC_dump.
2198 =item LOG.DDMMYYYY or LOG.DDMMYYYY.z
2200 Last month's log file. Log files are aged monthly and compressed
2201 (if compression is enabled), and old LOG files are deleted.
2202 In earlier versions of BackupPC these files used to have
2203 a suffix of 0, 1, ....
2205 =item XferERR or XferERR.z
2207 Output from the transport program (ie: smbclient, tar or rsync)
2208 for the most recent failed backup.
2212 Subdirectory in which the current backup is stored. This
2213 directory is renamed if the backup succeeds.
2215 =item XferLOG or XferLOG.z
2217 Output from the transport program (ie: smbclient, tar or rsync)
2218 for the current backup.
2220 =item nnn (an integer)
2222 Successful backups are in directories numbered sequentially starting at 0.
2224 =item XferLOG.nnn or XferLOG.nnn.z
2226 Output from the transport program (ie: smbclient, tar or rsync)
2227 corresponding to backup number nnn.
2229 =item RestoreInfo.nnn
2231 Information about restore request #nnn including who, what, when, and
2232 why. This file is in Data::Dumper format. (Note that the restore
2233 numbers are not related to the backup number.)
2235 =item RestoreLOG.nnn.z
2237 Output from smbclient, tar or rsync during restore #nnn. (Note that the restore
2238 numbers are not related to the backup number.)
2240 =item ArchiveInfo.nnn
2242 Information about archive request #nnn including who, what, when, and
2243 why. This file is in Data::Dumper format. (Note that the archive
2244 numbers are not related to the restore or backup number.)
2246 =item ArchiveLOG.nnn.z
2248 Output from archive #nnn. (Note that the archive numbers are not related
2249 to the backup or restore number.)
2253 Old location of optional configuration settings specific to this host.
2254 Settings in this file override the main configuration file.
2255 In new versions of BackupPC the per-host configuration files are
2256 stored in __CONFDIR__/pc/HOST.pl.
2260 A tab-delimited ascii table listing information about each successful
2261 backup, one per row. The columns are:
2267 The backup number, an integer that starts at 0 and increments
2268 for each successive backup. The corresponding backup is stored
2269 in the directory num (eg: if this field is 5, then the backup is
2270 stored in __TOPDIR__/pc/$host/5).
2274 Set to "full" or "incr" for full or incremental backup.
2278 Start time of the backup in unix seconds.
2282 Stop time of the backup in unix seconds.
2286 Number of files backed up (as reported by smbclient, tar or rsync).
2290 Total file size backed up (as reported by smbclient, tar or rsync).
2294 Number of files that were already in the pool
2295 (as determined by BackupPC_dump and BackupPC_link).
2299 Total size of files that were already in the pool
2300 (as determined by BackupPC_dump and BackupPC_link).
2304 Number of files that were not in the pool
2305 (as determined by BackupPC_link).
2309 Total size of files that were not in the pool
2310 (as determined by BackupPC_link).
2314 Number of errors or warnings from smbclient, tar or rsync.
2318 Number of errors from smbclient that were bad file errors (zero otherwise).
2322 Number of errors from smbclient that were bad share errors (zero otherwise).
2326 Number of errors from BackupPC_tarExtract.
2330 The compression level used on this backup. Zero or empty means no
2335 Total compressed size of files that were already in the pool
2336 (as determined by BackupPC_dump and BackupPC_link).
2340 Total compressed size of files that were not in the pool
2341 (as determined by BackupPC_link).
2345 Set if this backup has not been filled in with the most recent
2346 previous filled or full backup. See $Conf{IncrFill}.
2350 If this backup was filled (ie: noFill is 0) then this is the
2351 number of the backup that it was filled from
2355 Set if this backup has mangled file names and attributes. Always
2356 true for backups in v1.4.0 and above. False for all backups prior
2361 Set to the value of $Conf{XferMethod} when this dump was done.
2365 The level of this dump. A full dump is level 0. Currently incrementals
2366 are 1. But when multi-level incrementals are supported this will reflect
2367 each dump's incremental level.
2373 A tab-delimited ascii table listing information about each requested
2374 restore, one per row. The columns are:
2380 Restore number (matches the suffix of the RestoreInfo.nnn and
2381 RestoreLOG.nnn.z file), unrelated to the backup number.
2385 Start time of the restore in unix seconds.
2389 End time of the restore in unix seconds.
2393 Result (ok or failed).
2397 Error message if restore failed.
2401 Number of files restored.
2405 Size in bytes of the restored files.
2409 Number of errors from BackupPC_tarCreate during restore.
2413 Number of errors from smbclient, tar or rsync during restore.
2419 A tab-delimited ascii table listing information about each requested
2420 archive, one per row. The columns are:
2426 Archive number (matches the suffix of the ArchiveInfo.nnn and
2427 ArchiveLOG.nnn.z file), unrelated to the backup or restore number.
2431 Start time of the restore in unix seconds.
2435 End time of the restore in unix seconds.
2439 Result (ok or failed).
2443 Error message if archive failed.
2451 =head2 Compressed file format
2453 The compressed file format is as generated by Compress::Zlib::deflate
2454 with one minor, but important, tweak. Since Compress::Zlib::inflate
2455 fully inflates its argument in memory, it could take large amounts of
2456 memory if it was inflating a highly compressed file. For example, a
2457 200MB file of 0x0 bytes compresses to around 200K bytes. If
2458 Compress::Zlib::inflate was called with this single 200K buffer, it
2459 would need to allocate 200MB of memory to return the result.
2461 BackupPC watches how efficiently a file is compressing. If a big file
2462 has very high compression (meaning it will use too much memory when it
2463 is inflated), BackupPC calls the flush() method, which gracefully
2464 completes the current compression. BackupPC then starts another
2465 deflate and simply appends the output file. So the BackupPC compressed
2466 file format is one or more concatenated deflations/flushes. The specific
2467 ratios that BackupPC uses is that if a 6MB chunk compresses to less
2468 than 64K then a flush will be done.
2470 Back to the example of the 200MB file of 0x0 bytes. Adding flushes
2471 every 6MB adds only 200 or so bytes to the 200K output. So the
2472 storage cost of flushing is negligible.
2474 To easily decompress a BackupPC compressed file, the script
2475 BackupPC_zcat can be found in __INSTALLDIR__/bin. For each
2476 file name argument it inflates the file and writes it to stdout.
2478 =head2 Rsync checksum caching
2480 An incremental backup with rsync compares attributes on the client
2481 with the last full backup. Any files with identical attributes
2482 are skipped. A full backup with rsync sets the --ignore-times
2483 option, which causes every file to be examined independent of
2486 Each file is examined by generating block checksums (default 2K
2487 blocks) on the receiving side (that's the BackupPC side), sending
2488 those checksums to the client, where the remote rsync matches those
2489 checksums with the corresponding file. The matching blocks and new
2490 data is sent back, allowing the client file to be reassembled.
2491 A checksum for the entire file is sent to as an extra check the
2492 the reconstructed file is correct.
2494 This results in significant disk IO and computation for BackupPC:
2495 every file in a full backup, or any file with non-matching attributes
2496 in an incremental backup, needs to be uncompressed, block checksums
2497 computed and sent. Then the receiving side reassembles the file and
2498 has to verify the whole-file checksum. Even if the file is identical,
2499 prior to 2.1.0, BackupPC had to read and uncompress the file twice,
2500 once to compute the block checksums and later to verify the whole-file
2503 Starting in 2.1.0, BackupPC supports optional checksum caching,
2504 which means the block and file checksums only need to be computed
2505 once for each file. This results in a significant performance
2506 improvement. This only works for compressed pool files.
2507 It is enabled by adding
2509 '--checksum-seed=32761',
2511 to $Conf{RsyncArgs} and $Conf{RsyncRestoreArgs}.
2513 Rsync versions prior to and including rsync-2.6.2 need a small patch to
2514 add support for the --checksum-seed option. This patch is available in
2515 the cygwin-rsyncd package at L<http://backuppc.sourceforge.net>.
2516 This patch is already included in rsync CVS, so it will be standard
2517 in future versions of rsync.
2519 When this option is present, BackupPC will add block and file checksums
2520 to the compressed pool file the next time a pool file is used and it
2521 doesn't already have cached checksums. The first time a new file is
2522 written to the pool, the checksums are not appended. The next time
2523 checksums are needed for a file, they are computed and added. So the
2524 full performance benefit of checksum caching won't be noticed until the
2525 third time a pool file is used (eg: the third full backup).
2527 With checksum caching enabled, there is a risk that should a file's contents
2528 in the pool be corrupted due to a disk problem, but the cached checksums
2529 are still correct, the corruption will not be detected by a full backup,
2530 since the file contents are no longer read and compared. To reduce the
2531 chance that this remains undetected, BackupPC can recheck cached checksums
2532 for a fraction of the files. This fraction is set with the
2533 $Conf{RsyncCsumCacheVerifyProb} setting. The default value of 0.01 means
2534 that 1% of the time a file's checksums are read, the checksums are verified.
2535 This reduces performance slightly, but, over time, ensures that files
2536 contents are in sync with the cached checksums.
2538 The format of the cached checksum data can be discovered by looking at
2539 the code. Basically, the first byte of the compressed file is changed
2540 to denote that checksums are appended. The block and file checksum
2541 data, plus some other information and magic word, are appended to the
2542 compressed file. This allows the cache update to be done in-place.
2544 =head2 File name mangling
2546 Backup file names are stored in "mangled" form. Each node of
2547 a path is preceded by "f" (mnemonic: file), and special characters
2548 (\n, \r, % and /) are URI-encoded as "%xx", where xx is the ascii
2549 character's hex value. So c:/craig/example.txt is now stored as
2550 fc/fcraig/fexample.txt.
2552 This was done mainly so meta-data could be stored alongside the backup
2553 files without name collisions. In particular, the attributes for the
2554 files in a directory are stored in a file called "attrib", and mangling
2555 avoids file name collisions (I discarded the idea of having a duplicate
2556 directory tree for every backup just to store the attributes). Other
2557 meta-data (eg: rsync checksums) could be stored in file names preceded
2558 by, eg, "c". There are two other benefits to mangling: the share name
2559 might contain "/" (eg: "/home/craig" for tar transport), and I wanted
2560 that represented as a single level in the storage tree. Secondly, as
2561 files are written to NewFileList for later processing by BackupPC_link,
2562 embedded newlines in the file's path will cause problems which are
2563 avoided by mangling.
2565 The CGI script undoes the mangling, so it is invisible to the user.
2566 Old (unmangled) backups are still supported by the CGI
2569 =head2 Special files
2571 Linux/unix file systems support several special file types: symbolic
2572 links, character and block device files, fifos (pipes) and unix-domain
2573 sockets. All except unix-domain sockets are supported by BackupPC
2574 (there's no point in backing up or restoring unix-domain sockets since
2575 they only have meaning after a process creates them). Symbolic links are
2576 stored as a plain file whose contents are the contents of the link (not
2577 the file it points to). This file is compressed and pooled like any
2578 normal file. Character and block device files are also stored as plain
2579 files, whose contents are two integers separated by a comma; the numbers
2580 are the major and minor device number. These files are compressed and
2581 pooled like any normal file. Fifo files are stored as empty plain files
2582 (which are not pooled since they have zero size). In all cases, the
2583 original file type is stored in the attrib file so it can be correctly
2586 Hardlinks are also supported. When GNU tar first encounters a file with
2587 more than one link (ie: hardlinks) it dumps it as a regular file. When
2588 it sees the second and subsequent hardlinks to the same file, it dumps
2589 just the hardlink information. BackupPC correctly recognizes these
2590 hardlinks and stores them just like symlinks: a regular text file
2591 whose contents is the path of the file linked to. The CGI script
2592 will download the original file when you click on a hardlink.
2594 Also, BackupPC_tarCreate has enough magic to re-create the hardlinks
2595 dynamically based on whether or not the original file and hardlinks
2596 are both included in the tar file. For example, imagine a/b/x is a
2597 hardlink to a/c/y. If you use BackupPC_tarCreate to restore directory
2598 a, then the tar file will include a/b/x as the original file and a/c/y
2599 will be a hardlink to a/b/x. If, instead you restore a/c, then the
2600 tar file will include a/c/y as the original file, not a hardlink.
2602 =head2 Attribute file format
2604 The unix attributes for the contents of a directory (all the files and
2605 directories in that directory) are stored in a file called attrib.
2606 There is a single attrib file for each directory in a backup.
2607 For example, if c:/craig contains a single file c:/craig/example.txt,
2608 that file would be stored as fc/fcraig/fexample.txt and there would be an
2609 attribute file in fc/fcraig/attrib (and also fc/attrib and ./attrib).
2610 The file fc/fcraig/attrib would contain a single entry containing the
2611 attributes for fc/fcraig/fexample.txt.
2613 The attrib file starts with a magic number, followed by the
2614 concatenation of the following information for each file:
2620 File name length in perl's pack "w" format (variable length base 128).
2628 The unix file type, mode, uid, gid and file size divided by 4GB and
2629 file size modulo 4GB (type mode uid gid sizeDiv4GB sizeMod4GB),
2630 in perl's pack "w" format (variable length base 128).
2634 The unix mtime (unix seconds) in perl's pack "N" format (32 bit integer).
2638 The attrib file is also compressed if compression is enabled.
2639 See the lib/BackupPC/Attrib.pm module for full details.
2641 Attribute files are pooled just like normal backup files. This saves
2642 space if all the files in a directory have the same attributes across
2643 multiple backups, which is common.
2645 =head2 Optimizations
2647 BackupPC doesn't care about the access time of files in the pool
2648 since it saves attribute meta-data separate from the files. Since
2649 BackupPC mostly does reads from disk, maintaining the access time of
2650 files generates a lot of unnecessary disk writes. So, provided
2651 BackupPC has a dedicated data disk, you should consider mounting
2652 BackupPC's data directory with the noatime attribute (see mount(1)).
2656 BackupPC isn't perfect (but it is getting better). Please see
2657 L<http://backuppc.sourceforge.net/faq/limitations.html> for a
2658 discussion of some of BackupPC's limitations.
2660 =head2 Security issues
2662 Please see L<http://backuppc.sourceforge.net/faq/security.html> for a
2663 discussion of some of various security issues.
2665 =head1 Configuration File
2667 The BackupPC configuration file resides in __CONFDIR__/config.pl.
2668 Optional per-PC configuration files reside in __CONFDIR__/pc/$host.pl
2669 (or __TOPDIR__/pc/$host/config.pl in non-FHS versions of BackupPC).
2670 This file can be used to override settings just for a particular PC.
2672 =head2 Modifying the main configuration file
2674 The configuration file is a perl script that is executed by BackupPC, so
2675 you should be careful to preserve the file syntax (punctuation, quotes
2676 etc) when you edit it. It is recommended that you use CVS, RCS or some
2677 other method of source control for changing config.pl.
2679 BackupPC reads or re-reads the main configuration file and
2680 the hosts file in three cases:
2690 When BackupPC is sent a HUP (-1) signal. Assuming you installed the
2691 init.d script, you can also do this with "/etc/init.d/backuppc reload".
2695 When the modification time of config.pl file changes. BackupPC
2696 checks the modification time once during each regular wakeup.
2700 Whenever you change the configuration file you can either do
2701 a kill -HUP BackupPC_pid or simply wait until the next regular
2704 Each time the configuration file is re-read a message is reported in the
2705 LOG file, so you can tail it (or view it via the CGI interface) to make
2706 sure your kill -HUP worked. Errors in parsing the configuration file are
2707 also reported in the LOG file.
2709 The optional per-PC configuration file (__CONFDIR__/pc/$host.pl or
2710 __TOPDIR__/pc/$host/config.pl in non-FHS versions of BackupPC)
2711 is read whenever it is needed by BackupPC_dump, BackupPC_link and others.
2713 =head1 Configuration Parameters
2715 The configuration parameters are divided into five general groups.
2716 The first group (general server configuration) provides general
2717 configuration for BackupPC. The next two groups describe what to
2718 backup, when to do it, and how long to keep it. The fourth group
2719 are settings for email reminders, and the final group contains
2720 settings for the CGI interface.
2722 All configuration settings in the second through fifth groups can
2723 be overridden by the per-PC config.pl file.
2727 =head1 Version Numbers
2729 Starting with v1.4.0 BackupPC uses a X.Y.Z version numbering system,
2730 instead of X.0Y. The first digit is for major new releases, the middle
2731 digit is for significant feature releases and improvements (most of
2732 the releases have been in this category), and the last digit is for
2733 bug fixes. You should think of the old 1.00, 1.01, 1.02 and 1.03 as
2734 1.0.0, 1.1.0, 1.2.0 and 1.3.0.
2736 Additionally, patches might be made available. A patched version
2737 number is of the form X.Y.ZplN (eg: 2.1.0pl2), where N is the
2742 Craig Barratt <cbarratt@users.sourceforge.net>
2744 See L<http://backuppc.sourceforge.net>.
2748 Copyright (C) 2001-2007 Craig Barratt
2752 Ryan Kucera contributed the directory navigation code and images
2753 for v1.5.0. He contributed the first skeleton of BackupPC_restore.
2754 He also added a significant revision to the CGI interface, including
2755 CSS tags, in v2.1.0, and designed the BackupPC logo.
2757 Xavier Nicollet, with additions from Guillaume Filion, added the
2758 internationalization (i18n) support to the CGI interface for v2.0.0.
2759 Xavier provided the French translation fr.pm, with additions from
2762 Guillaume Filion wrote BackupPC_zipCreate and added the CGI support
2763 for zip download, in addition to some CGI cleanup, for v1.5.0.
2764 Guillaume continues to support fr.pm updates for each new version.
2766 Josh Marshall implemented the Archive feature in v2.1.0.
2768 Ludovic Drolez supports the BackupPC Debian package.
2770 Javier Gonzalez provided the Spanish translation, es.pm for v2.0.0.
2772 Manfred Herrmann provided the German translation, de.pm for v2.0.0.
2773 Manfred continues to support de.pm updates for each new version,
2774 together with some help from Ralph Paßgang.
2776 Lorenzo Cappelletti provided the Italian translation, it.pm for v2.1.0.
2777 Giuseppe Iuculano and Vittorio Macchi updated it for 3.0.0.
2779 Lieven Bridts provided the Dutch translation, nl.pm, for v2.1.0,
2780 with some tweaks from Guus Houtzager, and updates for 3.0.0.
2782 Reginaldo Ferreira provided the Portuguese Brazillian translation
2783 pt_br.pm for v2.2.0.
2785 Rich Duzenbury provided the RSS feed option to the CGI interface.
2787 Jono Woodhouse from CapeSoft Software (www.capesoft.com) provided a
2788 new CSS skin for 3.0.0 with several layout improvements. Sean Cameron
2789 (also from CapeSoft) designed new and more compact file icons for 3.0.0.
2791 Youlin Feng provided the Chinese translation for 3.1.0.
2793 Jeremy Tietsort provided the host summary table sorting feature for 3.1.0.
2795 Many people have reported bugs, made useful suggestions and helped
2796 with testing; see the ChangeLog and the mail lists.
2798 Your name could appear here in the next version!
2802 This program is free software; you can redistribute it and/or modify it
2803 under the terms of the GNU General Public License as published by the
2804 Free Software Foundation; either version 2 of the License, or (at your
2805 option) any later version.
2807 This program is distributed in the hope that it will be useful,
2808 but WITHOUT ANY WARRANTY; without even the implied warranty of
2809 MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
2810 General Public License for more details.
2812 You should have received a copy of the GNU General Public License in the
2813 LICENSE file along with this program; if not, write to the Free Software
2814 Foundation, Inc., 59 Temple Place, Suite 330, Boston, MA 02111-1307 USA.