1 =head1 BackupPC Introduction
3 This documentation describes BackupPC version __VERSION__,
4 released on __RELEASEDATE__.
8 BackupPC is a high-performance, enterprise-grade system for backing up
9 Unix, Linux and WinXX PCs, desktops and laptops to a server's disk.
10 BackupPC is highly configurable and easy to install and maintain.
12 Given the ever decreasing cost of disks and raid systems, it is now
13 practical and cost effective to backup a large number of machines onto
14 a server's local disk or network storage. For some sites this might be
15 the complete backup solution. For other sites additional permanent
16 archives could be created by periodically backing up the server to tape.
24 A clever pooling scheme minimizes disk storage and disk I/O.
25 Identical files across multiple backups of the same or different PC
26 are stored only once (using hard links), resulting in substantial
27 savings in disk storage and disk writes.
31 Optional compression provides additional reductions in storage
32 (around 40%). The CPU impact of compression is low since only
33 new files (those not already in the pool) need to be compressed.
37 A powerful http/cgi user interface allows administrators to view log
38 files, configuration, current status and allows users to initiate and
39 cancel backups and browse and restore files from backups.
43 The http/cgi user interface has internationalization (i18n) support,
44 currently providing English, French, German, Spanish, Italian
49 No client-side software is needed. On WinXX the standard smb
50 protocol is used to extract backup data. On linux or unix clients,
51 rsync or tar (over ssh/rsh/nfs) is used to extract backup data.
52 Alternatively, rsync can also be used on WinXX (using cygwin),
53 and Samba could be installed on the linux or unix client to
58 Flexible restore options. Single files can be downloaded from
59 any backup directly from the CGI interface. Zip or Tar archives
60 for selected files or directories from any backup can also be
61 downloaded from the CGI interface. Finally, direct restore to
62 the client machine (using smb or tar) for selected files or
63 directories is also supported from the CGI interface.
67 BackupPC supports mobile environments where laptops are only
68 intermittently connected to the network and have dynamic IP addresses
69 (DHCP). Configuration settings allow machines connected via slower WAN
70 connections (eg: dial up, DSL, cable) to not be backed up, even if they
71 use the same fixed or dynamic IP address as when they are connected
76 Flexible configuration parameters allow multiple backups to be performed
77 in parallel, specification of which shares to backup, which directories
78 to backup or not backup, various schedules for full and incremental
79 backups, schedules for email reminders to users and so on. Configuration
80 parameters can be set system-wide or also on a per-PC basis.
84 Users are sent periodic email reminders if their PC has not
85 recently been backed up. Email content, timing and policies
90 BackupPC is Open Source software hosted by SourceForge.
100 A full backup is a complete backup of a share. BackupPC can be
101 configured to do a full backup at a regular interval (typically
102 weekly). BackupPC can be configured to keep a certain number
103 of full backups. Exponential expiry is also supported, allowing
104 full backups with various vintages to be kept (for example, a
105 settable number of most recent weekly fulls, plus a settable
106 number of older fulls that are 2, 4, 8, or 16 weeks apart).
108 =item Incremental Backup
110 An incremental backup is a backup of files that have changed (based on
111 their modification time) since the last successful full backup. For
112 SMB and tar, BackupPC backups all files that have changed since one
113 hour prior to the start of the last successful full backup. Rsync is
114 more clever: any files whose attributes have changed (ie: uid, gid,
115 mtime, modes, size) since the last full are backed up. Deleted, new
116 files and renamed files are detected by Rsync incrementals.
117 In constrast, SMB and tar incrementals are not able to detect deleted
118 files, renamed files or new files whose modification time is prior to
121 BackupPC can also be configured to keep a certain number of incremental
122 backups, and to keep a smaller number of very old incremental backups.
123 (BackupPC does not support multi-level incremental backups, although it
124 will in a future version.)
126 BackupPC's CGI interface "fills-in" incremental backups based on the
127 last full backup, giving every backup a "full" appearance. This makes
128 browsing and restoring backups easier.
132 When a full backup fails or is canceled, and some files have already
133 been backed up, BackupPC keeps a partial backup containing just the
134 files that were backed up successfully. The partial backup is removed
135 when the next successful backup completes, or if another full backup
136 fails resulting in a newer partial backup. A failed full backup
137 that has not backed up any files, or any failed incremental backup,
138 is removed; no partial backup is saved in these cases.
140 The partial backup may be browsed or used to restore files just like
141 a successful full or incremental backup.
143 With the rsync transfer method the partial backup is used to resume
144 the next full backup, avoiding the need to retransfer the file data
145 already in the partial backup.
147 =item Identical Files
149 BackupPC pools identical files using hardlinks. By "identical
150 files" we mean files with identical contents, not necessary the
151 same permissions, ownership or modification time. Two files might
152 have different permissions, ownership, or modification time but
153 will still be pooled whenever the contents are identical. This
154 is possible since BackupPC stores the file meta-data (permissions,
155 ownership, and modification time) separately from the file contents.
159 Based on your site's requirements you need to decide what your backup
160 policy is. BackupPC is not designed to provide exact re-imaging of
161 failed disks. See L<Limitations|limitations> for more information.
162 However, the addition of tar transport for linux/unix clients, plus
163 full support for special file types and unix attributes in v1.4.0
164 likely means an exact image of a linux/unix file system can be made.
166 BackupPC saves backups onto disk. Because of pooling you can relatively
167 economically keep several weeks of old backups.
169 At some sites the disk-based backup will be adequate, without a
170 secondary tape backup. This system is robust to any single failure: if a
171 client disk fails or loses files, the BackupPC server can be used to
172 restore files. If the server disk fails, BackupPC can be restarted on a
173 fresh file system, and create new backups from the clients. The chance
174 of the server disk failing can be made very small by spending more money
175 on increasingly better RAID systems. However, there is still the risk
176 of catastrophic events like fires or earthquakes that can destroy
177 both the BackupPC server and the clients it is backing up if they
178 are physically nearby.
180 Some sites might choose to do periodic backups to tape or cd/dvd.
181 This backup can be done perhaps weekly using the archive function of
184 Other users have reported success with removable disks to rotate the
185 BackupPC data drives, or using rsync to mirror the BackupPC data pool
194 =item BackupPC home page
196 The BackupPC Open Source project is hosted on SourceForge. The
197 home page can be found at:
199 http://backuppc.sourceforge.net
201 This page has links to the current documentation, the SourceForge
202 project page and general information.
204 =item SourceForge project
206 The SourceForge project page is at:
208 http://sourceforge.net/projects/backuppc
210 This page has links to the current releases of BackupPC.
214 BackupPC has a FAQ at L<http://backuppc.sourceforge.net/faq>.
218 Three BackupPC mailing lists exist for announcements (backuppc-announce),
219 developers (backuppc-devel), and a general user list for support, asking
220 questions or any other topic relevant to BackupPC (backuppc-users).
222 The lists are archived on SourceForge and Gmane. The SourceForge lists
223 are not always up to date and the searching is limited, so Gmane is
224 a good alternative. See:
226 http://news.gmane.org/index.php?prefix=gmane.comp.sysutils.backup.backuppc
227 http://sourceforge.net/mailarchive/forum.php?forum_id=503
229 You can subscribe to these lists by visiting:
231 http://lists.sourceforge.net/lists/listinfo/backuppc-announce
232 http://lists.sourceforge.net/lists/listinfo/backuppc-users
233 http://lists.sourceforge.net/lists/listinfo/backuppc-devel
235 The backuppc-announce list is moderated and is used only for
236 important announcements (eg: new versions). It is low traffic.
237 You only need to subscribe to one of backuppc-announce and
238 backuppc-users: backuppc-users also receives any messages on
241 The backuppc-devel list is only for developers who are working on BackupPC.
242 Do not post questions or support requests there. But detailed technical
243 discussions should happen on this list.
245 To post a message to the backuppc-users list, send an email to
247 backuppc-users@lists.sourceforge.net
249 Do not send subscription requests to this address!
251 =item Other Programs of Interest
253 If you want to mirror linux or unix files or directories to a remote server
254 you should consider rsync, L<http://rsync.samba.org>. BackupPC now uses
255 rsync as a transport mechanism; if you are already an rsync user you
256 can think of BackupPC as adding efficient storage (compression and
257 pooling) and a convenient user interface to rsync.
259 Unison is a utility that can do two-way, interactive, synchronization.
260 See L<http://www.cis.upenn.edu/~bcpierce/unison>.
262 Three popular open source packages that do tape backup are
263 Amanda (L<http://www.amanda.org>),
264 afbackup (L<http://sourceforge.net/projects/afbackup>), and
265 Bacula (L<http://www.bacula.org>).
266 Amanda can also backup WinXX machines to tape using samba.
267 These packages can be used as back ends to BackupPC to backup the
268 BackupPC server data to tape.
270 Various programs and scripts use rsync to provide hardlinked backups.
271 See, for example, Mike Rubel's site (L<http://www.mikerubel.org/computers/rsync_snapshots>),
272 JW Schultz's dirvish (L<http://www.dirvish.org/>),
273 Ben Escoto's rdiff-backup (L<http://rdiff-backup.stanford.edu>),
274 and John Bowman's rlbackup (L<http://www.math.ualberta.ca/imaging/rlbackup>).
276 BackupPC provides many additional features, such as compressed storage,
277 hardlinking any matching files (rather than just files with the same name),
278 and storing special files without root privileges. But these other scripts
279 provide simple and effective solutions and are worthy of consideration.
285 The new features planned for future releases of BackupPC
286 are at L<http://backuppc.sourceforge.net/faq/roadMap.html>.
288 Comments and suggestions are welcome.
292 BackupPC is free. I work on BackupPC because I enjoy doing it and I like
293 to contribute to the open source community.
295 BackupPC already has more than enough features for my own needs. The
296 main compensation for continuing to work on BackupPC is knowing that
297 more and more people find it useful. So feedback is certainly
298 appreciated, both positive and negative.
300 Beyond being a satisfied user and telling other people about it, everyone
301 is encouraged to add links to L<http://backuppc.sourceforge.net>
302 (I'll see them via Google) or otherwise publicize BackupPC. Unlike
303 the commercial products in this space, I have a zero budget (in both
304 time and money) for marketing, PR and advertising, so it's up to
305 all of you! Feel free to vote for BackupPC at
306 L<http://freshmeat.net/projects/backuppc>.
308 Also, everyone is encouraged to contribute patches, bug reports, feature
309 and design suggestions, new code, FAQs, and documentation corrections or
310 improvements. Answering questions on the mail list is a big help too.
312 =head1 Installing BackupPC
322 A linux, solaris, or unix based server with a substantial amount of free
323 disk space (see the next section for what that means). The CPU and disk
324 performance on this server will determine how many simultaneous backups
325 you can run. You should be able to run 4-8 simultaneous backups on a
326 moderately configured server.
328 Several users have reported significantly better performance using
329 reiser compared to ext3 for the BackupPC data file system. It is
330 also recommended you consider either an LVM or raid setup (either
331 in HW or SW; eg: 3Ware RAID5) so that you can expand the
332 file system as necessary.
334 When BackupPC starts with an empty pool, all the backup data will be
335 written to the pool on disk. After more backups are done, a higher
336 percentage of incoming files will already be in the pool. BackupPC is
337 able to avoid writing to disk new files that are already in the pool.
338 So over time disk writes will reduce significantly (by perhaps a factor
339 of 20 or more), since eventually 95% or more of incoming backup files
340 are typically in the pool. Disk reads from the pool are still needed to
341 do file compares to verify files are an exact match. So, with a mature
342 pool, if a relatively fast client generates data at say 1MB/sec, and you
343 run 4 simultaneous backups, there will be an average server disk load of
344 about 4MB/sec reads and 0.2MB/sec writes (assuming 95% of the incoming
345 files are in the pool). These rates will be perhaps 40% lower if
350 Perl version 5.6.0 or later. BackupPC has been tested with
351 version 5.6.x, and 5.8.x. If you don't have perl, please
352 see L<http://www.cpan.org>.
356 Perl modules Compress::Zlib, Archive::Zip and File::RsyncP. Try "perldoc
357 Compress::Zlib" and "perldoc Archive::Zip" to see if you have these
358 modules. If not, fetch them from L<http://www.cpan.org> and see the
359 instructions below for how to build and install them.
361 The File::RsyncP module is available from L<http://perlrsync.sourceforge.net>
362 or CPAN. You'll need to install the File::RsyncP module if you want to use
363 Rsync as a transport method.
367 If you are using smb to backup WinXX machines you need smbclient and
368 nmblookup from the samba package. You will also need nmblookup if
369 you are backing up linux/unix DHCP machines. See L<http://www.samba.org>.
370 Version 2.2.0 or later of Samba is required.
371 Samba versions 3.x are stable and now recommended instead of 2.x.
373 See L<http://www.samba.org> for source and binaries. It's pretty easy to
374 fetch and compile samba, and just grab smbclient and nmblookup, without
375 doing the installation. Alternatively, L<http://www.samba.org> has binary
376 distributions for most platforms.
380 If you are using tar to backup linux/unix machines you should have version
381 1.13.7 at a minimum, with version 1.13.20 or higher recommended. Use
382 "tar --version" to check your version. Various GNU mirrors have the newest
383 versions of tar, see for example L<http://www.funet.fi/pub/gnu/alpha/gnu/tar>.
384 As of June 2003 the latest version is 1.13.25.
388 If you are using rsync to backup linux/unix machines you should have
389 version 2.5.5 or higher on each client machine. See
390 L<http://rsync.samba.org>. Use "rsync --version" to check your version.
392 For BackupPC to use Rsync you will also need to install the perl
393 File::RsyncP module, which is available from
394 L<http://perlrsync.sourceforge.net>.
395 Version 0.52 or later is required.
399 The Apache web server, see L<http://www.apache.org>, preferably built
400 with mod_perl support.
404 =head2 How much disk space do I need?
406 Here's one real example for an environment that is backing up 65 laptops
407 with compression off. Each full backup averages 3.2GB. Each incremental
408 backup averages about 0.2GB. Storing one full backup and two incremental
409 backups per laptop is around 240GB of raw data. But because of the
410 pooling of identical files, only 87GB is used. This is without
413 Another example, with compression on: backing up 95 laptops, where
414 each backup averages 3.6GB and each incremental averages about 0.3GB.
415 Keeping three weekly full backups, and six incrementals is around
416 1200GB of raw data. Because of pooling and compression, only 150GB
419 Here's a rule of thumb. Add up the disk usage of all the machines you
420 want to backup (210GB in the first example above). This is a rough
421 minimum space estimate that should allow a couple of full backups and at
422 least half a dozen incremental backups per machine. If compression is on
423 you can reduce the storage requirements by maybe 30-40%. Add some margin
424 in case you add more machines or decide to keep more old backups.
426 Your actual mileage will depend upon the types of clients, operating
427 systems and applications you have. The more uniform the clients and
428 applications the bigger the benefit from pooling common files.
430 For example, the Eudora email tool stores each mail folder in a separate
431 file, and attachments are extracted as separate files. So in the sadly
432 common case of a large attachment emailed to many recipients, Eudora
433 will extract the attachment into a new file. When these machines are
434 backed up, only one copy of the file will be stored on the server, even
435 though the file appears in many different full or incremental backups. In
436 this sense Eudora is a "friendly" application from the point of view of
437 backup storage requirements.
439 An example at the other end of the spectrum is Outlook. Everything
440 (email bodies, attachments, calendar, contact lists) is stored in a
441 single file, which often becomes huge. Any change to this file requires
442 a separate copy of the file to be saved during backup. Outlook is even
443 more troublesome, since it keeps this file locked all the time, so it
444 cannot be read by smbclient whenever Outlook is running. See the
445 L<Limitations|limitations> section for more discussion of this problem.
447 In addition to total disk space, you shold make sure you have
448 plenty of inodes on your BackupPC data partition. Some users have
449 reported running out of inodes on their BackupPC data partition.
450 So even if you have plenty of disk space, BackupPC will report
451 failures when the inodes are exhausted. This is a particular
452 problem with ext2/ext3 file systems that have a fixed number of
453 inodes when the file system is built. Use "df -i" to see your
456 =head2 Step 1: Getting BackupPC
458 Some linux distributions now include BackupPC. The Debian
459 distribution, supprted by Ludovic Drolez, can be found at
460 L<http://packages.debian.org/backuppc>; it should be included
461 in the next stable Debian release. On Debian, BackupPC can
462 be installed with the command:
464 apt-get install backuppc
466 In the future there might be packages for Gentoo and other
467 linux flavors. If the packaged version is older than the
468 released version then you will probably want to install the
469 lastest version as described below.
471 Otherwise, manually fetching and installing BackupPC is easy.
472 Start by downloading the latest version from
473 L<http://backuppc.sourceforge.net>. Hit the "Code" button,
474 then select the "backuppc" or "backuppc-beta" package and
475 download the latest version.
477 =head2 Step 2: Installing the distribution
479 First off, there are three perl modules you should install.
480 These are all optional, but highly recommended:
486 To enable compression, you will need to install Compress::Zlib
487 from L<http://www.cpan.org>.
488 You can run "perldoc Compress::Zlib" to see if this module is installed.
492 To support restore via Zip archives you will need to install
493 Archive::Zip, also from L<http://www.cpan.org>.
494 You can run "perldoc Archive::Zip" to see if this module is installed.
498 To use rsync and rsyncd with BackupPC you will need to install File::RsyncP.
499 You can run "perldoc File::RsyncP" to see if this module is installed.
500 File::RsyncP is available from L<http://perlrsync.sourceforge.net>.
501 Version 0.52 or later is required.
505 To build and install these packages, fetch the tar.gz file and
506 then run these commands:
508 tar zxvf Archive-Zip-1.01.tar.gz
515 The same sequence of commands can be used for each module.
517 Now let's move onto BackupPC itself. After fetching
518 BackupPC-__VERSION__.tar.gz, run these commands as root:
520 tar zxf BackupPC-__VERSION__.tar.gz
521 cd BackupPC-__VERSION__
524 In the future this release might also have patches available on the
525 SourceForge site. These patch files are text files, with a name of
528 BackupPC-__VERSION__plN.diff
530 where N is the patch level, eg: pl5 is patch-level 5. These
531 patch files are cumulative: you only need apply the last patch
532 file, not all the earlier patch files. If a patch file is
533 available, eg: BackupPC-__VERSION__pl5.diff, you should apply
534 the patch after extracting the tar file:
536 # fetch BackupPC-__VERSION__.tar.gz
537 # fetch BackupPC-__VERSION__pl5.diff
538 tar zxf BackupPC-__VERSION__.tar.gz
539 cd BackupPC-__VERSION__
540 patch -p0 < ../BackupPC-__VERSION__pl5.diff
543 A patch file includes comments that describe that bug fixes
544 and changes. Feel free to review it before you apply the patch.
546 The configure.pl script also accepts command-line options if you
547 wish to run it in a non-interactive manner. It has self-contained
548 documentation for all the command-line options, which you can
553 When you run configure.pl you will be prompted for the full paths
554 of various executables, and you will be prompted for the following
561 It is best if BackupPC runs as a special user, eg backuppc, that has
562 limited privileges. It is preferred that backuppc belongs to a system
563 administrator group so that sys admin members can browse backuppc files,
564 edit the configuration files and so on. Although configurable, the
565 default settings leave group read permission on pool files, so make
566 sure the BackupPC user's group is chosen restrictively.
568 On this installation, this is __BACKUPPCUSER__.
572 You need to decide where to put the data directory, below which
573 all the BackupPC data is stored. This needs to be a big file system.
575 On this installation, this is __TOPDIR__.
577 =item Install Directory
579 You should decide where the BackupPC scripts, libraries and documentation
580 should be installed, eg: /opt/local/BackupPC.
582 On this installation, this is __INSTALLDIR__.
584 =item CGI bin Directory
586 You should decide where the BackupPC CGI script resides. This will
587 usually below Apache's cgi-bin directory.
589 On this installation, this is __CGIDIR__.
591 =item Apache image directory
593 A directory where BackupPC's images are stored so that Apache can
594 serve them. This should be somewhere under Apache's DocumentRoot
599 =head2 Step 3: Setting up config.pl
601 After running configure.pl, browse through the config file,
602 __TOPDIR__/conf/config.pl, and make sure all the default settings
603 are correct. In particular, you will need to decide whether to use
604 smb, tar or rsync transport (or whether to set it on a per-PC basis)
605 and set the relevant parameters for that transport method.
606 See the section L<Client Setup|step 5: client setup> for more details.
608 =head2 Step 4: Setting up the hosts file
610 The file __TOPDIR__/conf/hosts contains the list of clients to backup.
611 BackupPC reads this file in three cases:
621 When BackupPC is sent a HUP (-1) signal. Assuming you installed the
622 init.d script, you can also do this with "/etc/init.d/backuppc reload".
626 When the modification time of the hosts file changes. BackupPC
627 checks the modification time once during each regular wakeup.
631 Whenever you change the hosts file (to add or remove a host) you can
632 either do a kill -HUP BackupPC_pid or simply wait until the next regular
635 Each line in the hosts file contains three fields, separated
642 This is typically the host name or NetBios name of the client machine
643 and should be in lower case. The host name can contain spaces (escape
644 with a backslash), but it is not recommended.
646 Please read the section L<How BackupPC Finds Hosts|how backuppc finds hosts>.
648 In certain cases you might want several distinct clients to refer
649 to the same physical machine. For example, you might have a database
650 you want to backup, and you want to bracket the backup of the database
651 with shutdown/restart using $Conf{DumpPreUserCmd} and $Conf{DumpPostUserCmd}.
652 But you also want to backup the rest of the machine while the database
653 is still running. In the case you can specify two different clients in
654 the host file, using any mnemonic name (eg: myhost_mysql and myhost), and
655 use $Conf{ClientNameAlias} in myhost_mysql's config.pl to specify the
656 real host name of the machine.
660 Starting with v2.0.0 the way hosts are discovered has changed and now
661 in most cases you should specify 0 for the DHCP flag, even if the host
662 has a dynamically assigned IP address.
663 Please read the section L<How BackupPC Finds Hosts|how backuppc finds hosts>
664 to understand whether you need to set the DHCP flag.
666 You only need to set DHCP to 1 if your client machine doesn't
667 respond to the NetBios multicast request:
671 but does respond to a request directed to its IP address:
675 If you do set DHCP to 1 on any client you will need to specify the range of
676 DHCP addresses to search is specified in $Conf{DHCPAddressRanges}.
678 Note also that the $Conf{ClientNameAlias} feature does not work for
679 clients with DHCP set to 1.
683 This should be the unix login/email name of the user who "owns" or uses
684 this machine. This is the user who will be sent email about this
685 machine, and this user will have permission to stop/start/browse/restore
686 backups for this host. Leave this blank if no specific person should
687 receive email or be allowed to stop/start/browse/restore backups
688 for this host. Administrators will still have full permissions.
692 Additional user names, separate by commas and with no white space,
693 can be specified. These users will also have full permission in
694 the CGI interface to stop/start/browse/restore backups for this host.
695 These users will not be sent email about this host.
699 The first non-comment line of the hosts file is special: it contains
700 the names of the columns and should not be edited.
702 Here's a simple example of a hosts file:
704 host dhcp user moreUsers
705 farside 0 craig jim,dave
708 =head2 Step 5: Client Setup
710 Two methods for getting backup data from a client are supported: smb and
711 tar. Smb or rsync are the preferred methods for WinXX clients and rsync or
712 tar are the preferred methods for linux/unix clients.
714 The transfer method is set using the $Conf{XferMethod} configuration
715 setting. If you have a mixed environment (ie: you will use smb for some
716 clients and tar for others), you will need to pick the most common
717 choice for $Conf{XferMethod} for the main config.pl file, and then
718 override it in the per-PC config file for those hosts that will use
719 the other method. (Or you could run two completely separate instances
720 of BackupPC, with different data directories, one for WinXX and the
721 other for linux/unix, but then common files between the different
722 machine types will duplicated.)
724 Here are some brief client setup notes:
730 The preferred setup for WinXX clients is to set $Conf{XferMethod} to "smb".
731 (Actually, for v2.0.0, rsyncd is the better method for WinXX if you are
732 prepared to run rsync/cygwin on your WinXX client. More information
733 about this will be provided via the FAQ.)
735 If you want to use rsyncd for WinXX clients you can find a pre-packaged
736 zip file on L<http://backuppc.sourceforge.net>. The package is called
737 cygwin-rsync. It contains rsync.exe, template setup files and the
738 minimal set of cygwin libraries for everything to run. The README file
739 contains instructions for running rsync as a service, so it starts
740 automatically everytime you boot your machine.
742 If you build your own rsync, for rsync 2.6.2 it is strongly
743 recommended you apply the patch in the cygwin-rsync package on
744 L<http://backuppc.sourceforge.net>. This patch adds the --checksum-seed
745 option for checksum caching, and also sends all errors to the client,
746 which is important so BackupPC can log all file access errors.
749 Otherwise, to use SMB, you can either create shares for the data you want
750 to backup or your can use the existing C$ share. To create a new
751 share, open "My Computer", right click on the drive (eg: C), and
752 select "Sharing..." (or select "Properties" and select the "Sharing"
753 tab). In this dialog box you can enable sharing, select the share name
756 All Windows NT based OS (NT, 2000, XP Pro), are configured by default
757 to share the entire C drive as C$. This is a special share used for
758 various administration functions, one of which is to grant access to backup
759 operators. All you need to do is create a new domain user, specifically
760 for backup. Then add the new backup user to the built in "Backup
761 Operators" group. You now have backup capability for any directory on
762 any computer in the domain in one easy step. This avoids using
763 administrator accounts and only grants permission to do exactly what you
764 want for the given user, i.e.: backup.
765 Also, for additional security, you may wish to deny the ability for this
766 user to logon to computers in the default domain policy.
768 If this machine uses DHCP you will also need to make sure the
769 NetBios name is set. Go to Control Panel|System|Network Identification
770 (on Win2K) or Control Panel|System|Computer Name (on WinXP).
771 Also, you should go to Control Panel|Network Connections|Local Area
772 Connection|Properties|Internet Protocol (TCP/IP)|Properties|Advanced|WINS
773 and verify that NetBios is not disabled.
775 The relevant configuration settings are $Conf{SmbShareName},
776 $Conf{SmbShareUserName}, $Conf{SmbSharePasswd}, $Conf{SmbClientPath},
777 $Conf{SmbClientFullCmd}, $Conf{SmbClientIncrCmd} and
778 $Conf{SmbClientRestoreCmd}.
780 BackupPC needs to know the smb share user name and password for a
781 client machine that uses smb. The user name is specified in
782 $Conf{SmbShareUserName}. There are four ways to tell BackupPC the
789 As an environment variable BPC_SMB_PASSWD set before BackupPC starts.
790 If you start BackupPC manually the BPC_SMB_PASSWD variable must be set
791 manually first. For backward compatibility for v1.5.0 and prior, the
792 environment variable PASSWD can be used if BPC_SMB_PASSWD is not set.
793 Warning: on some systems it is possible to see environment variables of
798 Alternatively the BPC_SMB_PASSWD setting can be included in
799 /etc/init.d/backuppc, in which case you must make sure this file
800 is not world (other) readable.
804 As a configuration variable $Conf{SmbSharePasswd} in
805 __TOPDIR__/conf/config.pl. If you put the password
806 here you must make sure this file is not world (other) readable.
810 As a configuration variable $Conf{SmbSharePasswd} in the per-PC
811 configuration file, __TOPDIR__/pc/$host/config.pl. You will have to
812 use this option if the smb share password is different for each host.
813 If you put the password here you must make sure this file is not
814 world (other) readable.
818 Placement and protection of the smb share password is a possible
819 security risk, so please double-check the file and directory
820 permissions. In a future version there might be support for
821 encryption of this password, but a private key will still have to
822 be stored in a protected place. Suggestions are welcome.
824 As an alternative to setting $Conf{XferMethod} to "smb" (using
825 smbclient) for WinXX clients, you can use an smb network filesystem (eg:
826 ksmbfs or similar) on your linux/unix server to mount the share,
827 and then set $Conf{XferMethod} to "tar" (use tar on the network
828 mounted file system).
830 Also, to make sure that file names with 8-bit characters are correctly
831 transferred by smbclient you should add this to samba's smb.conf file
835 # Accept the windows charset
836 client code page = 850
837 character set = ISO8859-1
839 For samba 3.x this should instead be:
842 unix charset = ISO8859-1
844 This setting should work for western europe.
845 See L<http://www.oreilly.com/catalog/samba/chapter/book/ch08_03.html>
846 for more information about settings for other languages.
850 The preferred setup for linux/unix clients is to set $Conf{XferMethod}
851 to "rsync", "rsyncd" or "tar".
853 You can use either rsync, smb, or tar for linux/unix machines. Smb requires
854 that the Samba server (smbd) be run to provide the shares. Since the smb
855 protocol can't represent special files like symbolic links and fifos,
856 tar and rsync are the better transport methods for linux/unix machines.
857 (In fact, by default samba makes symbolic links look like the file or
858 directory that they point to, so you could get an infinite loop if a
859 symbolic link points to the current or parent directory. If you really
860 need to use Samba shares for linux/unix backups you should turn off the
861 "follow symlinks" samba config setting. See the smb.conf manual page.)
863 The requirements for each Xfer Method are:
869 You must have GNU tar on the client machine. Use "tar --version"
870 or "gtar --version" to verify. The version should be at least
871 1.13.7, and 1.13.20 or greater is recommended. Tar is run on
872 the client machine via rsh or ssh.
874 The relevant configuration settings are $Conf{TarClientPath},
875 $Conf{TarShareName}, $Conf{TarClientCmd}, $Conf{TarFullArgs},
876 $Conf{TarIncrArgs}, and $Conf{TarClientRestoreCmd}.
880 You should have at least rsync 2.5.5, and the latest version 2.5.6
881 is recommended. Rsync is run on the remote client via rsh or ssh.
883 The relevant configuration settings are $Conf{RsyncClientPath},
884 $Conf{RsyncClientCmd}, $Conf{RsyncClientRestoreCmd}, $Conf{RsyncShareName},
885 $Conf{RsyncArgs}, and $Conf{RsyncRestoreArgs}.
889 You should have at least rsync 2.5.5, and the latest version 2.6.2
890 is recommended. In this case the rsync daemon should be running on
891 the client machine and BackupPC connects directly to it.
893 The relevant configuration settings are $Conf{RsyncdClientPort},
894 $Conf{RsyncdUserName}, $Conf{RsyncdPasswd}, $Conf{RsyncdAuthRequired},
895 $Conf{RsyncShareName}, $Conf{RsyncArgs}, and $Conf{RsyncRestoreArgs}.
896 $Conf{RsyncShareName} is the name of an rsync module (ie: the thing
897 in square brackets in rsyncd's conf file -- see rsyncd.conf), not a
900 Be aware that rsyncd will remove the leading '/' from path names in
901 symbolic links if you specify "use chroot = no" in the rsynd.conf file.
902 See the rsyncd.conf manual page for more information.
906 For linux/unix machines you should not backup "/proc". This directory
907 contains a variety of files that look like regular files but they are
908 special files that don't need to be backed up (eg: /proc/kcore is a
909 regular file that contains physical memory). See $Conf{BackupFilesExclude}.
910 It is safe to back up /dev since it contains mostly character-special
911 and block-special files, which are correctly handed by BackupPC
912 (eg: backing up /dev/hda5 just saves the block-special file information,
913 not the contents of the disk).
915 Alternatively, rather than backup all the file systems as a single
916 share ("/"), it is easier to restore a single file system if you backup
917 each file system separately. To do this you should list each file system
918 mount point in $Conf{TarShareName} or $Conf{RsyncShareName}, and add the
919 --one-file-system option to $Conf{TarClientCmd} or add --one-file-system
920 (note the different punctuation) to $Conf{RsyncArgs}. In this case there
921 is no need to exclude /proc explicitly since it looks like a different
924 Next you should decide whether to run tar over ssh, rsh or nfs. Ssh is
925 the preferred method. Rsh is not secure and therefore not recommended.
926 Nfs will work, but you need to make sure that the BackupPC user (running
927 on the server) has sufficient permissions to read all the files below
930 Ssh allows BackupPC to run as a privileged user on the client (eg:
931 root), since it needs sufficient permissions to read all the backup
932 files. Ssh is setup so that BackupPC on the server (an otherwise low
933 privileged user) can ssh as root on the client, without being prompted
934 for a password. There are two common versions of ssh: v1 and v2. Here
935 are some instructions for one way to setup ssh. (Check which version
936 of SSH you have by typing "ssh" or "man ssh".)
940 In general this should be similar to Linux/Unix machines.
941 Mark Stosberg reports that you can also use hfstar.
942 See L<http://fink.sourceforge.net/pdb/package.php/hfstar>.
946 SSH is a secure way to run tar or rsync on a backup client to extract
947 the data. SSH provides strong authentication and encryption of
950 Note that if you run rsyncd (rsync daemon), ssh is not used.
951 In this case, rsyncd provides its own authentication, but there
952 is no encryption of network data. If you want encryption of
953 network data you can use ssh to create a tunnel, or use a
954 program like stunnel. If someone submits instructions I
956 Setup instructions for ssh are at
957 L<http://backuppc.sourceforge.net/faq/ssh.html>.
959 =item Clients that use DHCP
961 If a client machine uses DHCP BackupPC needs some way to find the
962 IP address given the host name. One alternative is to set dhcp
963 to 1 in the hosts file, and BackupPC will search a pool of IP
964 addresses looking for hosts. More efficiently, it is better to
965 set dhcp = 0 and provide a mechanism for BackupPC to find the
966 IP address given the host name.
968 For WinXX machines BackupPC uses the NetBios name server to determine
969 the IP address given the host name.
970 For unix machines you can run nmbd (the NetBios name server) from
971 the Samba distribution so that the machine responds to a NetBios
972 name request. See the manual page and Samba documentation for more
975 Alternatively, you can set $Conf{NmbLookupFindHostCmd} to any command
976 that returns the IP address given the host name.
978 Please read the section L<How BackupPC Finds Hosts|how backuppc finds hosts>
983 =head2 Step 6: Running BackupPC
985 The installation contains an init.d backuppc script that can be copied
986 to /etc/init.d so that BackupPC can auto-start on boot.
987 See init.d/README for further instructions.
989 BackupPC should be ready to start. If you installed the init.d script,
990 then you should be able to run BackupPC with:
992 /etc/init.d/backuppc start
994 (This script can also be invoked with "stop" to stop BackupPC and "reload"
995 to tell BackupPC to reload config.pl and the hosts file.)
999 __INSTALLDIR__/bin/BackupPC -d
1001 as user __BACKUPPCUSER__. The -d option tells BackupPC to run as a daemon
1002 (ie: it does an additional fork).
1004 Any immediate errors will be printed to stderr and BackupPC will quit.
1005 Otherwise, look in __TOPDIR__/log/LOG and verify that BackupPC reports
1006 it has started and all is ok.
1008 =head2 Step 7: Talking to BackupPC
1010 Note: as of version 1.5.0, BackupPC no longer supports telnet
1011 to its TCP port. First off, a unix domain socket is used
1012 instead of a TCP port. (The TCP port can still be re-enabled
1013 if your installation has apache and BackupPC running on different
1014 machines.) Secondly, even if you still use the TCP port, the
1015 messages exchanged over this interface are now protected by
1016 an MD5 digest based on a shared secret (see $Conf{ServerMesgSecret})
1017 as well as sequence numbers and per-session unique keys, preventing
1018 forgery and replay attacks.
1020 You should verify that BackupPC is running by using BackupPC_serverMesg.
1021 This sends a message to BackupPC via the unix (or TCP) socket and prints
1024 You can request status information and start and stop backups using this
1025 interface. This socket interface is mainly provided for the CGI interface
1026 (and some of the BackupPC sub-programs use it too). But right now we just
1027 want to make sure BackupPC is happy. Each of these commands should
1028 produce some status output:
1030 __INSTALLDIR__/bin/BackupPC_serverMesg status info
1031 __INSTALLDIR__/bin/BackupPC_serverMesg status jobs
1032 __INSTALLDIR__/bin/BackupPC_serverMesg status hosts
1034 The output should be some hashes printed with Data::Dumper. If it
1035 looks cryptic and confusing, and doesn't look like an error message,
1038 The jobs status should initially show just BackupPC_trashClean.
1039 The hosts status should produce a list of every host you have listed
1040 in __TOPDIR__/conf/hosts as part of a big cryptic output line.
1042 You can also request that all hosts be queued:
1044 __INSTALLDIR__/bin/BackupPC_serverMesg backup all
1046 At this point you should make sure the CGI interface works since
1047 it will be much easier to see what is going on. That's our
1050 =head2 Step 8: CGI interface
1052 The CGI interface script, BackupPC_Admin, is a powerful and flexible
1053 way to see and control what BackupPC is doing. It is written for an
1054 Apache server. If you don't have Apache, see L<http://www.apache.org>.
1056 There are two options for setting up the CGI interface: standard
1057 mode and using mod_perl. Mod_perl provides much higher performance
1058 (around 15x) and is the best choice if your Apache was built with
1059 mod_perl support. To see if your apache was built with mod_perl
1062 httpd -l | egrep mod_perl
1064 If this prints mod_perl.c then your Apache supports mod_perl.
1066 Using mod_perl with BackupPC_Admin requires a dedicated Apache
1067 to be run as the BackupPC user (__BACKUPPCUSER__). This is
1068 because BackupPC_Admin needs permission to access various files
1069 in BackupPC's data directories. In contrast, the standard
1070 installation (without mod_perl) solves this problem by having
1071 BackupPC_Admin installed as setuid to the BackupPC user, so that
1072 BackupPC_Admin runs as the BackuPC user.
1074 Here are some specifics for each setup:
1078 =item Standard Setup
1080 The CGI interface should have been installed by the configure.pl script
1081 in __CGIDIR__/BackupPC_Admin. BackupPC_Admin should have been installed
1082 as setuid to the BackupPC user (__BACKUPPCUSER__), in addition to user
1083 and group execute permission.
1085 You should be very careful about permissions on BackupPC_Admin and
1086 the directory __CGIDIR__: it is important that normal users cannot
1087 directly execute or change BackupPC_Admin, otherwise they can access
1088 backup files for any PC. You might need to change the group ownership
1089 of BackupPC_Admin to a group that Apache belongs to so that Apache
1090 can execute it (don't add "other" execute permission!).
1091 The permissions should look like this:
1093 ls -l __CGIDIR__/BackupPC_Admin
1094 -swxr-x--- 1 __BACKUPPCUSER__ web 82406 Jun 17 22:58 __CGIDIR__/BackupPC_Admin
1096 The setuid script won't work unless perl on your machine was installed
1097 with setuid emulation. This is likely the problem if you get an error
1098 saying such as "Wrong user: my userid is 25, instead of 150", meaning
1099 the script is running as the httpd user, not the BackupPC user.
1100 This is because setuid scripts are disabled by the kernel in most
1101 flavors of unix and linux.
1103 To see if your perl has setuid emulation, see if there is a program
1104 called sperl5.6.0 (or sperl5.8.2 etc, based on your perl version)
1105 in the place where perl is installed. If you can't find this program,
1106 then you have two options: rebuild and reinstall perl with the setuid
1107 emulation turned on (answer "y" to the question "Do you want to do
1108 setuid/setgid emulation?" when you run perl's configure script), or
1109 switch to the mod_perl alternative for the CGI script (which doesn't
1110 need setuid to work).
1112 =item Mod_perl Setup
1114 The advantage of the mod_perl setup is that no setuid script is needed,
1115 and there is a huge performance advantage. Not only does all the perl
1116 code need to be parsed just once, the config.pl and hosts files, plus
1117 the connection to the BackupPC server are cached between requests. The
1118 typical speedup is around 15 times.
1120 To use mod_perl you need to run Apache as user __BACKUPPCUSER__.
1121 If you need to run multiple Apache's for different services then
1122 you need to create multiple top-level Apache directories, each
1123 with their own config file. You can make copies of /etc/init.d/httpd
1124 and use the -d option to httpd to point each http to a different
1125 top-level directory. Or you can use the -f option to explicitly
1126 point to the config file. Multiple Apache's will run on different
1127 Ports (eg: 80 is standard, 8080 is a typical alternative port accessed
1128 via http://yourhost.com:8080).
1130 Inside BackupPC's Apache http.conf file you should check the
1131 settings for ServerRoot, DocumentRoot, User, Group, and Port. See
1132 L<http://httpd.apache.org/docs/server-wide.html> for more details.
1134 For mod_perl, BackupPC_Admin should not have setuid permission, so
1135 you should turn it off:
1137 chmod u-s __CGIDIR__/BackupPC_Admin
1139 To tell Apache to use mod_perl to execute BackupPC_Admin, add this
1140 to Apache's 1.x httpd.conf file:
1142 <IfModule mod_perl.c>
1143 PerlModule Apache::Registry
1145 <Location /cgi-bin/BackupPC/BackupPC_Admin> # <--- change path as needed
1146 SetHandler perl-script
1147 PerlHandler Apache::Registry
1153 Apache 2.0.44 with Perl 5.8.0 on RedHat 7.1, Don Silvia reports that
1154 this works (with tweaks from Michael Tuzi):
1156 LoadModule perl_module modules/mod_perl.so
1159 <Directory /path/to/cgi/>
1160 SetHandler perl-script
1161 PerlResponseHandler ModPerl::Registry
1162 PerlOptions +ParseHeaders
1166 Allow from 192.168.0
1167 AuthName "Backup Admin"
1169 AuthUserFile /path/to/user_file
1173 There are other optimizations and options with mod_perl. For
1174 example, you can tell mod_perl to preload various perl modules,
1175 which saves memory compared to loading separate copies in every
1176 Apache process after they are forked. See Stas's definitive
1177 mod_perl guide at L<http://perl.apache.org/guide>.
1181 BackupPC_Admin requires that users are authenticated by Apache.
1182 Specifically, it expects that Apache sets the REMOTE_USER environment
1183 variable when it runs. There are several ways to do this. One way
1184 is to create a .htaccess file in the cgi-bin directory that looks like:
1186 AuthGroupFile /etc/httpd/conf/group # <--- change path as needed
1187 AuthUserFile /etc/http/conf/passwd # <--- change path as needed
1192 You will also need "AllowOverride Indexes AuthConfig" in the Apache
1193 httpd.conf file to enable the .htaccess file. Alternatively, everything
1194 can go in the Apache httpd.conf file inside a Location directive. The
1195 list of users and password file above can be extracted from the NIS
1198 One alternative is to use LDAP. In Apache's http.conf add these lines:
1200 LoadModule auth_ldap_module modules/auth_ldap.so
1201 AddModule auth_ldap.c
1203 # cgi-bin - auth via LDAP (for BackupPC)
1204 <Location /cgi-binBackupPC/BackupPC_Admin> # <--- change path as needed
1206 AuthName "BackupPC login"
1207 # replace MYDOMAIN, PORT, ORG and CO as needed
1208 AuthLDAPURL ldap://ldap.MYDOMAIN.com:PORT/o=ORG,c=CO?uid?sub?(objectClass=*)
1212 If you want to disable the user authentication you can set
1213 $Conf{CgiAdminUsers} to '*', which allows any user to have
1214 full access to all hosts and backups. In this case the REMOTE_USER
1215 environment variable does not have to be set by Apache.
1217 Alternatively, you can force a particular user name by getting Apache
1218 to set REMOTE_USER, eg, to hardcode the user to www you could add
1219 this to Apache's httpd.conf:
1221 <Location /cgi-bin/BackupPC/BackupPC_Admin> # <--- change path as needed
1222 Setenv REMOTE_USER www
1225 Finally, you should also edit the config.pl file and adjust, as necessary,
1226 the CGI-specific settings. They're near the end of the config file. In
1227 particular, you should specify which users or groups have administrator
1228 (privileged) access: see the config settings $Conf{CgiAdminUserGroup}
1229 and $Conf{CgiAdminUsers}. Also, the configure.pl script placed various
1230 images into $Conf{CgiImageDir} that BackupPC_Admin needs to serve
1231 up. You should make sure that $Conf{CgiImageDirURL} is the correct
1232 URL for the image directory.
1234 See the section L<Fixing installation problems|fixing installation problems> for suggestions on debugging the Apache authentication setup.
1236 =head2 How BackupPC Finds Hosts
1238 Starting with v2.0.0 the way hosts are discovered has changed. In most
1239 cases you should specify 0 for the DHCP flag in the conf/hosts file,
1240 even if the host has a dynamically assigned IP address.
1242 BackupPC (starting with v2.0.0) looks up hosts with DHCP = 0 in this manner:
1248 First DNS is used to lookup the IP address given the client's name
1249 using perl's gethostbyname() function. This should succeed for machines
1250 that have fixed IP addresses that are known via DNS. You can manually
1251 see whether a given host have a DNS entry according to perls'
1252 gethostbyname function with this command:
1254 perl -e 'print(gethostbyname("myhost") ? "ok\n" : "not found\n");'
1258 If gethostbyname() fails, BackupPC then attempts a NetBios multicast to
1259 find the host. Provided your client machine is configured properly,
1260 it should respond to this NetBios multicast request. Specifically,
1261 BackupPC runs a command of this form:
1265 If this fails you will see output like:
1267 querying myhost on 10.10.255.255
1268 name_query failed to find name myhost
1270 If this success you will see output like:
1272 querying myhost on 10.10.255.255
1273 10.10.1.73 myhost<00>
1275 Depending on your netmask you might need to specify the -B option to
1276 nmblookup. For example:
1278 nmblookup -B 10.10.1.255 myhost
1280 If necessary, experiment on the nmblookup command that will return the
1281 IP address of the client given its name. Then update
1282 $Conf{NmbLookupFindHostCmd} with any necessary options to nmblookup.
1286 For hosts that have the DHCP flag set to 1, these machines are
1287 discovered as follows:
1293 A DHCP address pool ($Conf{DHCPAddressRanges}) needs to be specified.
1294 BackupPC will check the NetBIOS name of each machine in the range using
1295 a command of the form:
1297 nmblookup -A W.X.Y.Z
1299 where W.X.Y.Z is each candidate address from $Conf{DHCPAddressRanges}.
1300 Any host that has a valid NetBIOS name returned by this command (ie:
1301 matching an entry in the hosts file) will be backed up. You can
1302 modify the specific nmblookup command if necessary via $Conf{NmbLookupCmd}.
1306 You only need to use this DHCP feature if your client machine doesn't
1307 respond to the NetBios multicast request:
1311 but does respond to a request directed to its IP address:
1313 nmblookup -A W.X.Y.Z
1317 =head2 Other installation topics
1321 =item Removing a client
1323 If there is a machine that no longer needs to be backed up (eg: a retired
1324 machine) you have two choices. First, you can keep the backups accessible
1325 and browsable, but disable all new backups. Alternatively, you can
1326 completely remove the client and all its backups.
1328 To disable backups for a client there are two special values for
1329 $Conf{FullPeriod} in that client's per-PC config.pl file:
1335 Don't do any regular backups on this machine. Manually
1336 requested backups (via the CGI interface) will still occur.
1340 Don't do any backups on this machine. Manually requested
1341 backups (via the CGI interface) will be ignored.
1345 This will still allow that client's old backups to be browsable
1348 To completely remove a client and all its backups, you should remove its
1349 entry in the conf/hosts file, and then delete the __TOPDIR__/pc/$host
1350 directory. Whenever you change the hosts file, you should send
1351 BackupPC a HUP (-1) signal so that it re-reads the hosts file.
1352 If you don't do this, BackupPC will automatically re-read the
1353 hosts file at the next regular wakeup.
1355 Note that when you remove a client's backups you won't initially recover
1356 a lot of disk space. That's because the client's files are still in
1357 the pool. Overnight, when BackupPC_nightly next runs, all the unused
1358 pool files will be deleted and this will recover the disk space used
1359 by the client's backups.
1361 =item Copying the pool
1363 If the pool disk requirements grow you might need to copy the entire
1364 data directory to a new (bigger) file system. Hopefully you are lucky
1365 enough to avoid this by having the data directory on a RAID file system
1366 or LVM that allows the capacity to be grown in place by adding disks.
1368 The backup data directories contain large numbers of hardlinks. If
1369 you try to copy the pool the target directory will occupy a lot more
1370 space if the hardlinks aren't re-established.
1372 The GNU cp program with the -a option is aware of hardlinks and knows
1373 to re-establish them. So GNU cp -a is the recommended way to copy
1374 the data directory and pool. Don't forget to stop BackupPC while
1377 =item Compressing an existing pool
1379 If you are upgrading BackupPC and want to turn compression on you have
1386 Simply turn on compression. All new backups will be compressed. Both old
1387 (uncompressed) and new (compressed) backups can be browsed and viewed.
1388 Eventually, the old backups will expire and all the pool data will be
1389 compressed. However, until the old backups expire, this approach could
1390 require 60% or more additional pool storage space to store both
1391 uncompressed and compressed versions of the backup files.
1395 Convert all the uncompressed pool files and backups to compressed.
1396 The script __INSTALLDIR__/bin/BackupPC_compressPool does this.
1397 BackupPC must not be running when you run BackupPC_compressPool.
1398 Also, there must be no existing compressed backups when you
1399 run BackupPC_compressPool.
1401 BackupPC_compressPool compresses all the files in the uncompressed pool
1402 (__TOPDIR__/pool) and moves them to the compressed pool
1403 (__TOPDIR__/cpool). It rewrites the files in place, so that the
1404 existing hardlinks are not disturbed.
1408 The rest of this section discusses how to run BackupPC_compressPool.
1410 BackupPC_compressPool takes three command line options:
1416 Test mode: do everything except actually replace the pool files.
1417 Useful for estimating total run time without making any real
1422 Read check: re-read the compressed file and compare it against
1423 the original uncompressed file. Can only be used in test mode.
1427 Number of children to fork. BackupPC_compressPool can take a long time
1428 to run, so to speed things up it spawns four children, each working on a
1429 different part of the pool. You can change the number of children with
1434 Here are the recommended steps for running BackupPC_compressPool:
1440 Stop BackupPC (eg: "/etc/init.d/backuppc stop").
1444 Set $Conf{CompressLevel} to a non-zero number (eg: 3).
1448 Do a dry run of BackupPC_compressPool. Make sure you run this as
1449 the BackupPC user (__BACKUPPCUSER__):
1451 BackupPC_compressPool -t -r
1453 The -t option (test mode) makes BackupPC_compressPool do all the steps,
1454 but not actually change anything. The -r option re-reads the compressed
1455 file and compares it against the original.
1457 BackupPC_compressPool gives a status as it completes each 1% of the job.
1458 It also shows the cumulative compression ratio and estimated completion
1459 time. Once you are comfortable that things look ok, you can kill
1460 BackupPC_compressPool or wait for it to finish.
1464 Now you are ready to run BackupPC_compressPool for real. Once again,
1465 as the BackupPC user (__BACKUPPCUSER__), run:
1467 BackupPC_compressPool
1469 You should put the output into a file and tail this file. (The running
1470 time could be twice as long as the test mode since the test mode file
1471 writes are immediately followed by an unlink, so in test mode it is
1472 likely the file writes never make it to disk.)
1474 It is B<critical> that BackupPC_compressPool runs to completion before
1475 re-starting BackupPC. Before BackupPC_compressPool completes, none of
1476 the existing backups will be in a consistent state. If you must stop
1477 BackupPC_compressPool for some reason, send it an INT or TERM signal
1478 and give it several seconds (or more) to clean up gracefully.
1479 After that, you can re-run BackupPC_compressPool and it will start
1480 again where it left off. Once again, it is critical that it runs
1485 After BackupPC_compressPool completes you should have a complete set
1486 of compressed backups (and your disk usage should be lower). You
1487 can now re-start BackupPC.
1491 =head2 Fixing installation problems
1493 Please see the FAQ at L<http://backuppc.sourceforge.net/faq> for
1494 debugging suggestions.
1496 =head1 Restore functions
1498 BackupPC supports several different methods for restoring files. The
1499 most convenient restore options are provided via the CGI interface.
1500 Alternatively, backup files can be restored using manual commands.
1502 =head2 CGI restore options
1504 By selecting a host in the CGI interface, a list of all the backups
1505 for that machine will be displayed. By selecting the backup number
1506 you can navigate the shares and directory tree for that backup.
1508 BackupPC's CGI interface automatically fills incremental backups
1509 with the corresponding full backup, which means each backup has
1510 a filled appearance. Therefore, there is no need to do multiple
1511 restores from the incremental and full backups: BackupPC does all
1512 the hard work for you. You simply select the files and directories
1513 you want from the correct backup vintage in one step.
1515 You can download a single backup file at any time simply by selecting
1516 it. Your browser should prompt you with the file name and ask you
1517 whether to open the file or save it to disk.
1519 Alternatively, you can select one or more files or directories in
1520 the currently selected directory and select "Restore selected files".
1521 (If you need to restore selected files and directories from several
1522 different parent directories you will need to do that in multiple
1525 If you select all the files in a directory, BackupPC will replace
1526 the list of files with the parent directory. You will be presented
1527 with a screen that has three options:
1531 =item Option 1: Direct Restore
1533 With this option the selected files and directories are restored
1534 directly back onto the host, by default in their original location.
1535 Any old files with the same name will be overwritten, so use caution.
1536 You can optionally change the target host name, target share name,
1537 and target path prefix for the restore, allowing you to restore the
1538 files to a different location.
1540 Once you select "Start Restore" you will be prompted one last time
1541 with a summary of the exact source and target files and directories
1542 before you commit. When you give the final go ahead the restore
1543 operation will be queued like a normal backup job, meaning that it
1544 will be deferred if there is a backup currently running for that host.
1545 When the restore job is run, smbclient, tar, rsync or rsyncd is used
1546 (depending upon $Conf{XferMethod}) to actually restore the files.
1547 Sorry, there is currently no option to cancel a restore that has been
1550 A record of the restore request, including the result and list of
1551 files and directories, is kept. It can be browsed from the host's
1552 home page. $Conf{RestoreInfoKeepCnt} specifies how many old restore
1553 status files to keep.
1555 Note that for direct restore to work, the $Conf{XferMethod} must
1556 be able to write to the client. For example, that means an SMB
1557 share for smbclient needs to be writable, and the rsyncd module
1558 needs "read only" set to "false". This creates additional security
1559 risks. If you only create read-only SMB shares (which is a good
1560 idea), then the direct restore will fail. You can disable the
1561 direct restore option by setting $Conf{SmbClientRestoreCmd},
1562 $Conf{TarClientRestoreCmd} and $Conf{RsyncRestoreArgs} to undef.
1564 =item Option 2: Download Zip archive
1566 With this option a zip file containing the selected files and directories
1567 is downloaded. The zip file can then be unpacked or individual files
1568 extracted as necessary on the host machine. The compression level can be
1569 specified. A value of 0 turns off compression.
1571 When you select "Download Zip File" you should be prompted where to
1572 save the restore.zip file.
1574 BackupPC does not consider downloading a zip file as an actual
1575 restore operation, so the details are not saved for later browsing
1576 as in the first case. However, a mention that a zip file was
1577 downloaded by a particular user, and a list of the files, does
1578 appear in BackupPC's log file.
1580 =item Option 3: Download Tar archive
1582 This is identical to the previous option, except a tar file is downloaded
1583 rather than a zip file (and there is currently no compression option).
1587 =head2 Command-line restore options
1589 Apart from the CGI interface, BackupPC allows you to restore files
1590 and directories from the command line. The following programs can
1597 For each file name argument it inflates (uncompresses) the file and
1598 writes it to stdout. To use BackupPC_zcat you could give it the
1601 __INSTALLDIR__/bin/BackupPC_zcat __TOPDIR__/pc/host/5/fc/fcraig/fexample.txt > example.txt
1603 It's your responsibility to make sure the file is really compressed:
1604 BackupPC_zcat doesn't check which backup the requested file is from.
1605 BackupPC_zcat returns a non-zero status if it fails to uncompress
1608 =item BackupPC_tarCreate
1610 BackupPC_tarCreate creates a tar file for any files or directories in
1611 a particular backup. Merging of incrementals is done automatically,
1612 so you don't need to worry about whether certain files appear in the
1613 incremental or full backup.
1617 BackupPC_tarCreate [-t] [-h host] [-n dumpNum] [-s shareName]
1618 [-r pathRemove] [-p pathAdd] [-b BLOCKS] [-w writeBufSz]
1619 files/directories...
1621 The command-line files and directories are relative to the specified
1622 shareName. The tar file is written to stdout.
1624 The required options are:
1630 host from which the tar archive is created
1634 dump number from which the tar archive is created
1638 share name from which the tar archive is created
1648 print summary totals
1652 path prefix that will be replaced with pathAdd
1660 the tar block size, default is 20, meaning tar writes data in 20 * 512
1665 write buffer size, default 1048576 (1MB). You can increase this if
1666 you are trying to stream to a fast tape device.
1670 The -h, -n and -s options specify which dump is used to generate
1671 the tar archive. The -r and -p options can be used to relocate
1672 the paths in the tar archive so extracted files can be placed
1673 in a location different from their original location.
1675 =item BackupPC_zipCreate
1677 BackupPC_zipCreate creates a zip file for any files or directories in
1678 a particular backup. Merging of incrementals is done automatically,
1679 so you don't need to worry about whether certain files appear in the
1680 incremental or full backup.
1684 BackupPC_zipCreate [-t] [-h host] [-n dumpNum] [-s shareName]
1685 [-r pathRemove] [-p pathAdd] [-c compressionLevel]
1686 files/directories...
1688 The command-line files and directories are relative to the specified
1689 shareName. The zip file is written to stdout.
1691 The required options are:
1697 host from which the zip archive is created
1701 dump number from which the zip archive is created
1705 share name from which the zip archive is created
1715 print summary totals
1719 path prefix that will be replaced with pathAdd
1727 compression level (default is 0, no compression)
1731 The -h, -n and -s options specify which dump is used to generate
1732 the zip archive. The -r and -p options can be used to relocate
1733 the paths in the zip archive so extracted files can be placed
1734 in a location different from their original location.
1738 Each of these programs reside in __INSTALLDIR__/bin.
1740 =head1 Archive functions
1742 BackupPC supports archiving to removable media. For users that require
1743 offsite backups, BackupPC can create archives that stream to tape
1744 devices, or create files of specified sizes to fit onto cd or dvd media.
1746 Each archive type is specified by a BackupPC host with its XferMethod
1747 set to 'archive'. This allows for multiple configurations at sites where
1748 there might be a combination of tape and cd/dvd backups being made.
1750 BackupPC provides a menu that allows one or more hosts to be archived.
1751 The most recent backup of each host is archived using BackupPC_tarCreate,
1752 and the output is optionally compressed and split into fixed-sized
1755 The archive for each host is done by default using
1756 __INSTALLDIR__/BackupPC_archiveHost. This script can be copied
1757 and customized as needed.
1759 =head2 Configuring an Archive Host
1761 To create an Archive Host, add it to the hosts file just as any other host
1762 and call it a name that best describes the type of archive, e.g. ArchiveDLT
1764 To tell BackupPC that the Host is for Archives, create a config.pl file in
1765 the Archive Hosts's pc directory, adding the following line:
1767 $Conf{XferMethod} = 'archive';
1769 To further customise the archive's parameters you can adding the changed
1770 parameters in the host's config.pl file. The parameters are explained in
1771 the config.pl file. Parameters may be fixed or the user can be allowed
1772 to change them (eg: output device).
1774 The per-host archive command is $Conf{ArchiveClientCmd}. By default
1777 __INSTALLDIR__/BackupPC_archiveHost
1779 which you can copy and customize as necessary.
1781 =head2 Starting an Archive
1783 In the web interface, click on the Archive Host you wish to use. You will see a
1784 list of previous archives and a summary on each. By clicking the "Start Archive"
1785 button you are presented with the list of hosts and the approximate backup size
1786 (note this is raw size, not projected compressed size) Select the hosts you wish
1787 to archive and press the "Archive Selected Hosts" button.
1789 The next screen allows you to adjust the parameters for this archive run.
1790 Press the "Start the Archive" to start archiving the selected hosts with the
1791 parameters displayed.
1793 =head1 BackupPC Design
1795 =head2 Some design issues
1799 =item Pooling common files
1801 To quickly see if a file is already in the pool, an MD5 digest of the
1802 file length and contents is used as the file name in the pool. This
1803 can't guarantee a file is identical: it just reduces the search to
1804 often a single file or handful of files. A complete file comparison
1805 is always done to verify if two files are really the same.
1807 Identical files on multiples backups are represented by hard links.
1808 Hardlinks are used so that identical files all refer to the same
1809 physical file on the server's disk. Also, hard links maintain
1810 reference counts so that BackupPC knows when to delete unused files
1813 For the computer-science majors among you, you can think of the pooling
1814 system used by BackupPC as just a chained hash table stored on a (big)
1817 =item The hashing function
1819 There is a tradeoff between how much of file is used for the MD5 digest
1820 and the time taken comparing all the files that have the same hash.
1822 Using the file length and just the first 4096 bytes of the file for the
1823 MD5 digest produces some repetitions. One example: with 900,000 unique
1824 files in the pool, this hash gives about 7,000 repeated files, and in
1825 the worst case 500 files have the same hash. That's not bad: we only
1826 have to do a single file compare 99.2% of the time. But in the worst
1827 case we have to compare as many as 500 files checking for a match.
1829 With a modest increase in CPU time, if we use the file length and the
1830 first 256K of the file we now only have 500 repeated files and in the
1831 worst case around 20 files have the same hash. Furthermore, if we
1832 instead use the first and last 128K of the file (more specifically, the
1833 first and eighth 128K chunks for files larger than 1MB) we get only 300
1834 repeated files and in the worst case around 20 files have the same hash.
1836 Based on this experimentation, this is the hash function used by BackupPC.
1837 It is important that you don't change the hash function after files
1838 are already in the pool. Otherwise your pool will grow to twice the
1839 size until all the old backups (and all the old files with old hashes)
1844 BackupPC supports compression. It uses the deflate and inflate methods
1845 in the Compress::Zlib module, which is based on the zlib compression
1846 library (see L<http://www.gzip.org/zlib/>).
1848 The $Conf{CompressLevel} setting specifies the compression level to use.
1849 Zero (0) means no compression. Compression levels can be from 1 (least
1850 cpu time, slightly worse compression) to 9 (most cpu time, slightly
1851 better compression). The recommended value is 3. Changing it to 5, for
1852 example, will take maybe 20% more cpu time and will get another 2-3%
1853 additional compression. Diminishing returns set in above 5. See the zlib
1854 documentation for more information about compression levels.
1856 BackupPC implements compression with minimal CPU load. Rather than
1857 compressing every incoming backup file and then trying to match it
1858 against the pool, BackupPC computes the MD5 digest based on the
1859 uncompressed file, and matches against the candidate pool files by
1860 comparing each uncompressed pool file against the incoming backup file.
1861 Since inflating a file takes roughly a factor of 10 less CPU time than
1862 deflating there is a big saving in CPU time.
1864 The combination of pooling common files and compression can yield
1865 a factor of 8 or more overall saving in backup storage.
1869 =head2 BackupPC operation
1871 BackupPC reads the configuration information from
1872 __TOPDIR__/conf/config.pl. It then runs and manages all the backup
1873 activity. It maintains queues of pending backup requests, user backup
1874 requests and administrative commands. Based on the configuration various
1875 requests will be executed simultaneously.
1877 As specified by $Conf{WakeupSchedule}, BackupPC wakes up periodically
1878 to queue backups on all the PCs. This is a four step process:
1884 For each host and DHCP address backup requests are queued on the
1885 background command queue.
1889 For each PC, BackupPC_dump is forked. Several of these may be run in
1890 parallel, based on the configuration. First a ping is done to see if
1891 the machine is alive. If this is a DHCP address, nmblookup is run to
1892 get the netbios name, which is used as the host name. If DNS lookup
1893 fails, $Conf{NmbLookupFindHostCmd} is run to find the IP address from
1894 the host name. The file __TOPDIR__/pc/$host/backups is read to decide
1895 whether a full or incremental backup needs to be run. If no backup is
1896 scheduled, or the ping to $host fails, then BackupPC_dump exits.
1898 The backup is done using the specified XferMethod. Either samba's smbclient
1899 or tar over ssh/rsh/nfs piped into BackupPC_tarExtract, or rsync over ssh/rsh
1900 is run, or rsyncd is connected to, with the incoming data
1901 extracted to __TOPDIR__/pc/$host/new. The XferMethod output is put
1902 into __TOPDIR__/pc/$host/XferLOG.
1904 The letter in the XferLOG file shows the type of object, similar to the
1905 first letter of the modes displayed by ls -l:
1909 b -> block special file
1910 c -> character special file
1911 p -> pipe file (fifo)
1912 nothing -> regular file
1920 new for this backup (ie: directory or file not in pool)
1924 found a match in the pool
1928 file is identical to previous backup (contents were
1929 checksummed and verified during full dump).
1933 file skipped in incremental because attributes are the
1934 same (only displayed if $Conf{XferLogLevel} >= 2).
1938 As BackupPC_tarExtract extracts the files from smbclient or tar, or as
1939 rsync runs, it checks each file in the backup to see if it is identical
1940 to an existing file from any previous backup of any PC. It does this
1941 without needed to write the file to disk. If the file matches an
1942 existing file, a hardlink is created to the existing file in the pool.
1943 If the file does not match any existing files, the file is written to
1944 disk and the file name is saved in __TOPDIR__/pc/$host/NewFileList for
1945 later processing by BackupPC_link. BackupPC_tarExtract and rsync can handle
1946 arbitrarily large files and multiple candidate matching files without
1947 needing to write the file to disk in the case of a match. This
1948 significantly reduces disk writes (and also reads, since the pool file
1949 comparison is done disk to memory, rather than disk to disk).
1951 Based on the configuration settings, BackupPC_dump checks each
1952 old backup to see if any should be removed. Any expired backups
1953 are moved to __TOPDIR__/trash for later removal by BackupPC_trashClean.
1957 For each complete, good, backup, BackupPC_link is run.
1958 To avoid race conditions as new files are linked into the
1959 pool area, only a single BackupPC_link program runs
1960 at a time and the rest are queued.
1962 BackupPC_link reads the NewFileList written by BackupPC_dump and
1963 inspects each new file in the backup. It re-checks if there is a
1964 matching file in the pool (another BackupPC_link
1965 could have added the file since BackupPC_dump checked). If so, the file
1966 is removed and replaced by a hard link to the existing file. If the file
1967 is new, a hard link to the file is made in the pool area, so that this
1968 file is available for checking against each new file and new backup.
1970 Then, if $Conf{IncrFill} is set (note that the default setting is
1971 off), for each incremental backup, hard links are made in the new
1972 backup to all files that were not extracted during the incremental
1973 backups. The means the incremental backup looks like a complete
1974 image of the PC (with the exception that files that were removed on
1975 the PC since the last full backup will still appear in the backup
1978 The CGI interface knows how to merge unfilled incremental backups will
1979 the most recent prior filled (full) backup, giving the incremental
1980 backups a filled appearance. The default for $Conf{IncrFill} is off,
1981 since there is no need to fill incremental backups. This saves
1982 some level of disk activity, since lots of extra hardlinks are no
1983 longer needed (and don't have to be deleted when the backup expires).
1987 BackupPC_trashClean is always run in the background to remove any
1988 expired backups. Every 5 minutes it wakes up and removes all the files
1989 in __TOPDIR__/trash.
1991 Also, once each night, BackupPC_nightly is run to complete some additional
1992 administrative tasks, such as cleaning the pool. This involves removing
1993 any files in the pool that only have a single hard link (meaning no backups
1994 are using that file). Again, to avoid race conditions, BackupPC_nightly
1995 is only run when there are no BackupPC_dump or BackupPC_link processes
1996 running. Therefore, when it is time to run BackupPC_nightly, no new
1997 backups are started and BackupPC waits until all backups have finished.
1998 Then BackupPC_nightly is run, and until it finishes no new backups are
1999 started. If BackupPC_nightly takes too long to run, the settings
2000 $Conf{MaxBackupPCNightlyJobs} and $Conf{BackupPCNightlyPeriod} can
2001 be used to run several BackupPC_nightly processes in parallel, and
2002 to split its job over several nights.
2006 BackupPC also listens for TCP connections on $Conf{ServerPort}, which
2007 is used by the CGI script BackupPC_Admin for status reporting and
2008 user-initiated backup or backup cancel requests.
2010 =head2 Storage layout
2012 BackupPC resides in three directories:
2016 =item __INSTALLDIR__
2018 Perl scripts comprising BackupPC reside in __INSTALLDIR__/bin,
2019 libraries are in __INSTALLDIR__/lib and documentation
2020 is in __INSTALLDIR__/doc.
2024 The CGI script BackupPC_Admin resides in this cgi binary directory.
2028 All of BackupPC's data (PC backup images, logs, configuration information)
2029 is stored below this directory.
2033 Below __TOPDIR__ are several directories:
2037 =item __TOPDIR__/conf
2039 The directory __TOPDIR__/conf contains:
2045 Configuration file. See L<Configuration file|configuration file>
2046 below for more details.
2050 Hosts file, which lists all the PCs to backup.
2054 =item __TOPDIR__/log
2056 The directory __TOPDIR__/log contains:
2062 Current (today's) log file output from BackupPC.
2064 =item LOG.0 or LOG.0.z
2066 Yesterday's log file output. Log files are aged daily and compressed
2067 (if compression is enabled), and old LOG files are deleted.
2071 Contains BackupPC's process id.
2075 A summary of BackupPC's status written periodically by BackupPC so
2076 that certain state information can be maintained if BackupPC is
2077 restarted. Should not be edited.
2079 =item UserEmailInfo.pl
2081 A summary of what email was last sent to each user, and when the
2082 last email was sent. Should not be edited.
2086 =item __TOPDIR__/trash
2088 Any directories and files below this directory are periodically deleted
2089 whenever BackupPC_trashClean checks. When a backup is aborted or when an
2090 old backup expires, BackupPC_dump simply moves the directory to
2091 __TOPDIR__/trash for later removal by BackupPC_trashClean.
2093 =item __TOPDIR__/pool
2095 All uncompressed files from PC backups are stored below __TOPDIR__/pool.
2096 Each file's name is based on the MD5 hex digest of the file contents.
2097 Specifically, for files less than 256K, the file length and the entire
2098 file is used. For files up to 1MB, the file length and the first and
2099 last 128K are used. Finally, for files longer than 1MB, the file length,
2100 and the first and eighth 128K chunks for the file are used.
2102 Each file is stored in a subdirectory X/Y/Z, where X, Y, Z are the
2103 first 3 hex digits of the MD5 digest.
2105 For example, if a file has an MD5 digest of 123456789abcdef0,
2106 the file is stored in __TOPDIR__/pool/1/2/3/123456789abcdef0.
2108 The MD5 digest might not be unique (especially since not all the file's
2109 contents are used for files bigger than 256K). Different files that have
2110 the same MD5 digest are stored with a trailing suffix "_n" where n is
2111 an incrementing number starting at 0. So, for example, if two additional
2112 files were identical to the first, except the last byte was different,
2113 and assuming the file was larger than 1MB (so the MD5 digests are the
2114 same but the files are actually different), the three files would be
2117 __TOPDIR__/pool/1/2/3/123456789abcdef0
2118 __TOPDIR__/pool/1/2/3/123456789abcdef0_0
2119 __TOPDIR__/pool/1/2/3/123456789abcdef0_1
2121 Both BackupPC_dump (actually, BackupPC_tarExtract) and BackupPC_link are
2122 responsible for checking newly backed up files against the pool. For
2123 each file, the MD5 digest is used to generate a file name in the pool
2124 directory. If the file exists in the pool, the contents are compared.
2125 If there is no match, additional files ending in "_n" are checked.
2126 (Actually, BackupPC_tarExtract compares multiple candidate files in
2127 parallel.) If the file contents exactly match, the file is created by
2128 simply making a hard link to the pool file (this is done by
2129 BackupPC_tarExtract as the backup proceeds). Otherwise,
2130 BackupPC_tarExtract writes the new file to disk and a new hard link is
2131 made in the pool to the file (this is done later by BackupPC_link).
2133 Therefore, every file in the pool will have at least 2 hard links
2134 (one for the pool file and one for the backup file below __TOPDIR__/pc).
2135 Identical files from different backups or PCs will all be linked to
2136 the same file. When old backups are deleted, some files in the pool
2137 might only have one link. BackupPC_nightly checks the entire pool
2138 and removes all files that have only a single link, thereby recovering
2139 the storage for that file.
2141 One other issue: zero length files are not pooled, since there are a lot
2142 of these files and on most file systems it doesn't save any disk space
2143 to turn these files into hard links.
2145 =item __TOPDIR__/cpool
2147 All compressed files from PC backups are stored below __TOPDIR__/cpool.
2148 Its layout is the same as __TOPDIR__/pool, and the hashing function
2149 is the same (and, importantly, based on the uncompressed file, not
2150 the compressed file).
2152 =item __TOPDIR__/pc/$host
2154 For each PC $host, all the backups for that PC are stored below
2155 the directory __TOPDIR__/pc/$host. This directory contains the
2162 Current log file for this PC from BackupPC_dump.
2164 =item LOG.0 or LOG.0.z
2166 Last month's log file. Log files are aged monthly and compressed
2167 (if compression is enabled), and old LOG files are deleted.
2169 =item XferERR or XferERR.z
2171 Output from the transport program (ie: smbclient, tar or rsync)
2172 for the most recent failed backup.
2176 Subdirectory in which the current backup is stored. This
2177 directory is renamed if the backup succeeds.
2179 =item XferLOG or XferLOG.z
2181 Output from the transport program (ie: smbclient, tar or rsync)
2182 for the current backup.
2184 =item nnn (an integer)
2186 Successful backups are in directories numbered sequentially starting at 0.
2188 =item XferLOG.nnn or XferLOG.nnn.z
2190 Output from the transport program (ie: smbclient, tar or rsync)
2191 corresponding to backup number nnn.
2193 =item RestoreInfo.nnn
2195 Information about restore request #nnn including who, what, when, and
2196 why. This file is in Data::Dumper format. (Note that the restore
2197 numbers are not related to the backup number.)
2199 =item RestoreLOG.nnn.z
2201 Output from smbclient, tar or rsync during restore #nnn. (Note that the restore
2202 numbers are not related to the backup number.)
2204 =item ArchiveInfo.nnn
2206 Information about archive request #nnn including who, what, when, and
2207 why. This file is in Data::Dumper format. (Note that the archive
2208 numbers are not related to the restore or backup number.)
2210 =item ArchiveLOG.nnn.z
2212 Output from archive #nnn. (Note that the archive numbers are not related
2213 to the backup or restore number.)
2217 Optional configuration settings specific to this host. Settings in this
2218 file override the main configuration file.
2222 A tab-delimited ascii table listing information about each successful
2223 backup, one per row. The columns are:
2229 The backup number, an integer that starts at 0 and increments
2230 for each successive backup. The corresponding backup is stored
2231 in the directory num (eg: if this field is 5, then the backup is
2232 stored in __TOPDIR__/pc/$host/5).
2236 Set to "full" or "incr" for full or incremental backup.
2240 Start time of the backup in unix seconds.
2244 Stop time of the backup in unix seconds.
2248 Number of files backed up (as reported by smbclient, tar or rsync).
2252 Total file size backed up (as reported by smbclient, tar or rsync).
2256 Number of files that were already in the pool
2257 (as determined by BackupPC_dump and BackupPC_link).
2261 Total size of files that were already in the pool
2262 (as determined by BackupPC_dump and BackupPC_link).
2266 Number of files that were not in the pool
2267 (as determined by BackupPC_link).
2271 Total size of files that were not in the pool
2272 (as determined by BackupPC_link).
2276 Number of errors or warnings from smbclient, tar or rsync.
2280 Number of errors from smbclient that were bad file errors (zero otherwise).
2284 Number of errors from smbclient that were bad share errors (zero otherwise).
2288 Number of errors from BackupPC_tarExtract.
2292 The compression level used on this backup. Zero or empty means no
2297 Total compressed size of files that were already in the pool
2298 (as determined by BackupPC_dump and BackupPC_link).
2302 Total compressed size of files that were not in the pool
2303 (as determined by BackupPC_link).
2307 Set if this backup has not been filled in with the most recent
2308 previous filled or full backup. See $Conf{IncrFill}.
2312 If this backup was filled (ie: noFill is 0) then this is the
2313 number of the backup that it was filled from
2317 Set if this backup has mangled file names and attributes. Always
2318 true for backups in v1.4.0 and above. False for all backups prior
2323 Set to the value of $Conf{XferMethod} when this dump was done.
2327 The level of this dump. A full dump is level 0. Currently incrementals
2328 are 1. But when multi-level incrementals are supported this will reflect
2329 each dump's incremental level.
2335 A tab-delimited ascii table listing information about each requested
2336 restore, one per row. The columns are:
2342 Restore number (matches the suffix of the RestoreInfo.nnn and
2343 RestoreLOG.nnn.z file), unrelated to the backup number.
2347 Start time of the restore in unix seconds.
2351 End time of the restore in unix seconds.
2355 Result (ok or failed).
2359 Error message if restore failed.
2363 Number of files restored.
2367 Size in bytes of the restored files.
2371 Number of errors from BackupPC_tarCreate during restore.
2375 Number of errors from smbclient, tar or rsync during restore.
2381 A tab-delimited ascii table listing information about each requested
2382 archive, one per row. The columns are:
2388 Archive number (matches the suffix of the ArchiveInfo.nnn and
2389 ArchiveLOG.nnn.z file), unrelated to the backup or restore number.
2393 Start time of the restore in unix seconds.
2397 End time of the restore in unix seconds.
2401 Result (ok or failed).
2405 Error message if archive failed.
2413 =head2 Compressed file format
2415 The compressed file format is as generated by Compress::Zlib::deflate
2416 with one minor, but important, tweak. Since Compress::Zlib::inflate
2417 fully inflates its argument in memory, it could take large amounts of
2418 memory if it was inflating a highly compressed file. For example, a
2419 200MB file of 0x0 bytes compresses to around 200K bytes. If
2420 Compress::Zlib::inflate was called with this single 200K buffer, it
2421 would need to allocate 200MB of memory to return the result.
2423 BackupPC watches how efficiently a file is compressing. If a big file
2424 has very high compression (meaning it will use too much memory when it
2425 is inflated), BackupPC calls the flush() method, which gracefully
2426 completes the current compression. BackupPC then starts another
2427 deflate and simply appends the output file. So the BackupPC compressed
2428 file format is one or more concatenated deflations/flushes. The specific
2429 ratios that BackupPC uses is that if a 6MB chunk compresses to less
2430 than 64K then a flush will be done.
2432 Back to the example of the 200MB file of 0x0 bytes. Adding flushes
2433 every 6MB adds only 200 or so bytes to the 200K output. So the
2434 storage cost of flushing is negligible.
2436 To easily decompress a BackupPC compressed file, the script
2437 BackupPC_zcat can be found in __INSTALLDIR__/bin. For each
2438 file name argument it inflates the file and writes it to stdout.
2440 =head2 Rsync checksum caching
2442 An incremental backup with rsync compares attributes on the client
2443 with the last full backup. Any files with identical attributes
2444 are skipped. A full backup with rsync sets the --ignore-times
2445 option, which causes every file to be examined independent of
2448 Each file is examined by generating block checksums (default 2K
2449 blocks) on the receiving side (that's the BackupPC side), sending
2450 those checksums to the client, where the remote rsync matches those
2451 checksums with the corresponding file. The matching blocks and new
2452 data is sent back, allowing the client file to be reassembled.
2453 A checksum for the entire file is sent to as an extra check the
2454 the reconstructed file is correct.
2456 This results in significant disk IO and computation for BackupPC:
2457 every file in a full backup, or any file with non-matching attributes
2458 in an incremental backup, needs to be uncompressed, block checksums
2459 computed and sent. Then the receiving side reassembles the file and
2460 has to verify the whole-file checksum. Even if the file is identical,
2461 prior to 2.1.0, BackupPC had to read and uncompress the file twice,
2462 once to compute the block checksums and later to verify the whole-file
2465 Starting in 2.1.0, BackupPC supports optional checksum caching,
2466 which means the block and file checksums only need to be computed
2467 once for each file. This results in a significant performance
2468 improvement. This only works for compressed pool files.
2469 It is enabled by adding
2471 '--checksum-seed=32761',
2473 to $Conf{RsyncArgs} and $Conf{RsyncRestoreArgs}.
2475 Rsync versions prior to and including rsync-2.6.2 need a small patch to
2476 add support for the --checksum-seed option. This patch is available in
2477 the cygwin-rsyncd package at L<http://backuppc.sourceforge.net>.
2478 This patch is already included in rsync CVS, so it will be standard
2479 in future versions of rsync.
2481 When this option is present, BackupPC will add block and file checksums
2482 to the compressed pool file the next time a pool file is used and it
2483 doesn't already have cached checksums. The first time a new file is
2484 written to the pool, the checksums are not appended. The next time
2485 checksums are needed for a file, they are computed and added. So the
2486 full performance benefit of checksum caching won't be noticed until the
2487 third time a pool file is used (eg: the third full backup).
2489 With checksum caching enabled, there is a risk that should a file's contents
2490 in the pool be corrupted due to a disk problem, but the cached checksums
2491 are still correct, the corruption will not be detected by a full backup,
2492 since the file contents are no longer read and compared. To reduce the
2493 chance that this remains undetected, BackupPC can recheck cached checksums
2494 for a fraction of the files. This fraction is set with the
2495 $Conf{RsyncCsumCacheVerifyProb} setting. The default value of 0.01 means
2496 that 1% of the time a file's checksums are read, the checksums are verified.
2497 This reduces performance slightly, but, over time, ensures that files
2498 contents are in sync with the cached checksums.
2500 The format of the cached checksum data can be discovered by looking at
2501 the code. Basically, the first byte of the compressed file is changed
2502 to denote that checksums are appended. The block and file checksum
2503 data, plus some other information and magic word, are appended to the
2504 compressed file. This allows the cache update to be done in-place.
2506 =head2 File name mangling
2508 Backup file names are stored in "mangled" form. Each node of
2509 a path is preceded by "f" (mnemonic: file), and special characters
2510 (\n, \r, % and /) are URI-encoded as "%xx", where xx is the ascii
2511 character's hex value. So c:/craig/example.txt is now stored as
2512 fc/fcraig/fexample.txt.
2514 This was done mainly so meta-data could be stored alongside the backup
2515 files without name collisions. In particular, the attributes for the
2516 files in a directory are stored in a file called "attrib", and mangling
2517 avoids file name collisions (I discarded the idea of having a duplicate
2518 directory tree for every backup just to store the attributes). Other
2519 meta-data (eg: rsync checksums) could be stored in file names preceded
2520 by, eg, "c". There are two other benefits to mangling: the share name
2521 might contain "/" (eg: "/home/craig" for tar transport), and I wanted
2522 that represented as a single level in the storage tree. Secondly, as
2523 files are written to NewFileList for later processing by BackupPC_link,
2524 embedded newlines in the file's path will cause problems which are
2525 avoided by mangling.
2527 The CGI script undoes the mangling, so it is invisible to the user.
2528 Old (unmangled) backups are still supported by the CGI
2531 =head2 Special files
2533 Linux/unix file systems support several special file types: symbolic
2534 links, character and block device files, fifos (pipes) and unix-domain
2535 sockets. All except unix-domain sockets are supported by BackupPC
2536 (there's no point in backing up or restoring unix-domain sockets since
2537 they only have meaning after a process creates them). Symbolic links are
2538 stored as a plain file whose contents are the contents of the link (not
2539 the file it points to). This file is compressed and pooled like any
2540 normal file. Character and block device files are also stored as plain
2541 files, whose contents are two integers separated by a comma; the numbers
2542 are the major and minor device number. These files are compressed and
2543 pooled like any normal file. Fifo files are stored as empty plain files
2544 (which are not pooled since they have zero size). In all cases, the
2545 original file type is stored in the attrib file so it can be correctly
2548 Hardlinks are also supported. When GNU tar first encounters a file with
2549 more than one link (ie: hardlinks) it dumps it as a regular file. When
2550 it sees the second and subsequent hardlinks to the same file, it dumps
2551 just the hardlink information. BackupPC correctly recognizes these
2552 hardlinks and stores them just like symlinks: a regular text file
2553 whose contents is the path of the file linked to. The CGI script
2554 will download the original file when you click on a hardlink.
2556 Also, BackupPC_tarCreate has enough magic to re-create the hardlinks
2557 dynamically based on whether or not the original file and hardlinks
2558 are both included in the tar file. For example, imagine a/b/x is a
2559 hardlink to a/c/y. If you use BackupPC_tarCreate to restore directory
2560 a, then the tar file will include a/b/x as the original file and a/c/y
2561 will be a hardlink to a/b/x. If, instead you restore a/c, then the
2562 tar file will include a/c/y as the original file, not a hardlink.
2564 =head2 Attribute file format
2566 The unix attributes for the contents of a directory (all the files and
2567 directories in that directory) are stored in a file called attrib.
2568 There is a single attrib file for each directory in a backup.
2569 For example, if c:/craig contains a single file c:/craig/example.txt,
2570 that file would be stored as fc/fcraig/fexample.txt and there would be an
2571 attribute file in fc/fcraig/attrib (and also fc/attrib and ./attrib).
2572 The file fc/fcraig/attrib would contain a single entry containing the
2573 attributes for fc/fcraig/fexample.txt.
2575 The attrib file starts with a magic number, followed by the
2576 concatenation of the following information for each file:
2582 File name length in perl's pack "w" format (variable length base 128).
2590 The unix file type, mode, uid, gid and file size divided by 4GB and
2591 file size modulo 4GB (type mode uid gid sizeDiv4GB sizeMod4GB),
2592 in perl's pack "w" format (variable length base 128).
2596 The unix mtime (unix seconds) in perl's pack "N" format (32 bit integer).
2600 The attrib file is also compressed if compression is enabled.
2601 See the lib/BackupPC/Attrib.pm module for full details.
2603 Attribute files are pooled just like normal backup files. This saves
2604 space if all the files in a directory have the same attributes across
2605 multiple backups, which is common.
2607 =head2 Optimizations
2609 BackupPC doesn't care about the access time of files in the pool
2610 since it saves attribute meta-data separate from the files. Since
2611 BackupPC mostly does reads from disk, maintaining the access time of
2612 files generates a lot of unnecessary disk writes. So, provided
2613 BackupPC has a dedicated data disk, you should consider mounting
2614 BackupPC's data directory with the noatime attribute (see mount(1)).
2618 BackupPC isn't perfect (but it is getting better). Please see
2619 L<http://backuppc.sourceforge.net/faq/limitations.html> for a
2620 discussion of some of BackupPC's limitations.
2622 =head2 Security issues
2624 Please see L<http://backuppc.sourceforge.net/faq/security.html> for a
2625 discussion of some of various security issues.
2627 =head1 Configuration File
2629 The BackupPC configuration file resides in __TOPDIR__/conf/config.pl.
2630 Optional per-PC configuration files reside in __TOPDIR__/pc/$host/config.pl.
2631 This file can be used to override settings just for a particular PC.
2633 =head2 Modifying the main configuration file
2635 The configuration file is a perl script that is executed by BackupPC, so
2636 you should be careful to preserve the file syntax (punctuation, quotes
2637 etc) when you edit it. It is recommended that you use CVS, RCS or some
2638 other method of source control for changing config.pl.
2640 BackupPC reads or re-reads the main configuration file and
2641 the hosts file in three cases:
2651 When BackupPC is sent a HUP (-1) signal. Assuming you installed the
2652 init.d script, you can also do this with "/etc/init.d/backuppc reload".
2656 When the modification time of config.pl file changes. BackupPC
2657 checks the modification time once during each regular wakeup.
2661 Whenever you change the configuration file you can either do
2662 a kill -HUP BackupPC_pid or simply wait until the next regular
2665 Each time the configuration file is re-read a message is reported in the
2666 LOG file, so you can tail it (or view it via the CGI interface) to make
2667 sure your kill -HUP worked. Errors in parsing the configuration file are
2668 also reported in the LOG file.
2670 The optional per-PC configuration file (__TOPDIR__/pc/$host/config.pl)
2671 is read whenever it is needed by BackupPC_dump, BackupPC_link and others.
2673 =head2 Configuration file includes
2675 If you have a heterogeneous set of clients (eg: a variety of WinXX and
2676 linux/unix machines) you will need to create host-specific config.pl files
2677 for some or all of these machines to customize the default settings from
2678 the master config.pl file (at a minimum to set $Conf{XferMethod}).
2680 Since the config.pl file is just regular perl code, you can include
2681 one config file from another. For example, imagine you had three general
2682 classes of machines: WinXX desktops, linux machines in the DMZ and
2683 linux desktops. You could create three config files in __TOPDIR__/conf:
2685 __TOPDIR__/conf/ConfigWinDesktop.pl
2686 __TOPDIR__/conf/ConfigLinuxDMZ.pl
2687 __TOPDIR__/conf/ConfigLinuxDesktop.pl
2689 From each client's directory you can either add a symbolic link to
2690 the appropriate config file:
2692 cd __TOPDIR__/pc/$host
2693 ln -s ../../conf/ConfigWinDesktop.pl config.pl
2695 or, better yet, create a config.pl file in __TOPDIR__/pc/$host
2696 that includes the default config.pl file using perl's "do"
2699 do "__TOPDIR__/conf/ConfigWinDesktop.pl";
2701 This alternative allows you to set other configuration options
2702 specific to each host after the "do" command (perhaps even
2703 overriding the settings in the included file).
2705 Note that you could also include snippets of configuration settings
2706 from the main configuration file. However, be aware that the
2707 modification-time checking that BackupPC does only applies to the
2708 main configuration file: if you change one of the included files,
2709 BackupPC won't notice. You will need to either touch the main
2710 configuration file too, or send BackupPC a HUP (-1) signal.
2712 =head1 Configuration Parameters
2714 The configuration parameters are divided into five general groups.
2715 The first group (general server configuration) provides general
2716 configuration for BackupPC. The next two groups describe what to
2717 backup, when to do it, and how long to keep it. The fourth group
2718 are settings for email reminders, and the final group contains
2719 settings for the CGI interface.
2721 All configuration settings in the second through fifth groups can
2722 be overridden by the per-PC config.pl file.
2726 =head1 Version Numbers
2728 Starting with v1.4.0 BackupPC uses a X.Y.Z version numbering system,
2729 instead of X.0Y. The first digit is for major new releases, the middle
2730 digit is for significant feature releases and improvements (most of
2731 the releases have been in this category), and the last digit is for
2732 bug fixes. You should think of the old 1.00, 1.01, 1.02 and 1.03 as
2733 1..0, 1.1.0, 1.2.0 and 1.3.0.
2735 Additionally, patches might be made available. A patched version
2736 number is of the form X.Y.ZplN (eg: 2.1.0pl2), where N is the
2741 Craig Barratt <cbarratt@users.sourceforge.net>
2743 See L<http://backuppc.sourceforge.net>.
2747 Copyright (C) 2001-2005 Craig Barratt
2751 Ryan Kucera contributed the directory navigation code and images
2752 for v1.5.0. He contributed the first skeleton of BackupPC_restore.
2753 He also added a significant revision to the CGI interface, including
2754 CSS tags, in v2.1.0, and designed the BackupPC logo.
2756 Xavier Nicollet, with additions from Guillaume Filion, added the
2757 internationalization (i18n) support to the CGI interface for v2.0.0.
2758 Xavier provided the French translation fr.pm, with additions from
2761 Guillaume Filion wrote BackupPC_zipCreate and added the CGI support
2762 for zip download, in addition to some CGI cleanup, for v1.5.0.
2763 Guillaume continues to support fr.pm updates for each new version.
2765 Josh Marshall implemented the Archive feature in v2.1.0.
2767 Ludovic Drolez supports the BackupPC Debian package.
2769 Javier Gonzalez provided the Spanish translation, es.pm for v2.0.0.
2771 Manfred Herrmann provided the German translation, de.pm for v2.0.0.
2772 Manfred continues to support de.pm updates for each new version,
2773 together with some help frmo Ralph Paßgang.
2775 Lorenzo Cappelletti provided the Italian translation, it.pm for v2.1.0.
2777 Lieven Bridts provided the Dutch translation, nl.pm, for v2.1.0,
2778 with some tweaks from Guus Houtzager.
2780 Reginaldo Ferreira provided the Portuguese Brazillian translation
2781 pt_br.pm for v2.2.0.
2783 Many people have reported bugs, made useful suggestions and helped
2784 with testing; see the ChangeLog and the mail lists.
2786 Your name could appear here in the next version!
2790 This program is free software; you can redistribute it and/or modify it
2791 under the terms of the GNU General Public License as published by the
2792 Free Software Foundation; either version 2 of the License, or (at your
2793 option) any later version.
2795 This program is distributed in the hope that it will be useful,
2796 but WITHOUT ANY WARRANTY; without even the implied warranty of
2797 MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
2798 General Public License for more details.
2800 You should have received a copy of the GNU General Public License in the
2801 LICENSE file along with this program; if not, write to the Free Software
2802 Foundation, Inc., 59 Temple Place, Suite 330, Boston, MA 02111-1307 USA.