1 bup: It backs things up
2 =======================
4 bup is a program that backs things up. It's short for "backup." Can you
5 believe that nobody else has named an open source program "bup" after all
8 Despite its unassuming name, bup is pretty cool. To give you an idea of
9 just how cool it is, I wrote you this poem:
12 What rhymes with awesome?
14 But that's irrelevant.
16 Hmm. Did that help? Maybe prose is more useful after all.
19 Reasons bup is awesome
20 ----------------------
22 bup has a few advantages over other backup software:
24 - It uses a rolling checksum algorithm (similar to rsync) to split large
25 files into chunks. The most useful result of this is you can backup huge
26 virtual machine (VM) disk images, databases, and XML files incrementally,
27 even though they're typically all in one huge file, and not use tons of
28 disk space for multiple versions.
30 - It uses the packfile format from git (the open source version control
31 system), so you can access the stored data even if you don't like bup's
34 - Unlike git, it writes packfiles *directly* (instead of having a separate
35 garbage collection / repacking stage) so it's fast even with gratuitously
36 huge amounts of data. bup's improved index formats also allow you to
37 track far more filenames than git (millions) and keep track of far more
38 objects (hundreds or thousands of gigabytes).
40 - Data is "automagically" shared between incremental backups without having
41 to know which backup is based on which other one - even if the backups
42 are made from two different computers that don't even know about each
43 other. You just tell bup to back stuff up, and it saves only the minimum
44 amount of data needed.
46 - You can back up directly to a remote bup server, without needing tons of
47 temporary disk space on the computer being backed up. And if your backup
48 is interrupted halfway through, the next run will pick up where you left
49 off. And it's easy to set up a bup server: just install bup on any
50 machine where you have ssh access.
52 - Bup can use "par2" redundancy to recover corrupted backups even if your
53 disk has undetected bad sectors.
55 - Even when a backup is incremental, you don't have to worry about
56 restoring the full backup, then each of the incrementals in turn; an
57 incremental backup *acts* as if it's a full backup, it just takes less
60 - You can mount your bup repository as a FUSE filesystem and access the
61 content that way, and even export it over Samba.
63 - It's written in python (with some C parts to make it faster) so it's easy
64 for you to extend and maintain.
67 Reasons you might want to avoid bup
68 -----------------------------------
70 - It's not remotely as well tested as something like tar, so it's
71 more likely to eat your data. It's also missing some
72 probably-critical features, though fewer than it used to be.
74 - It requires python >= 2.6, a C compiler, and an installed git
75 version >= 1.5.6. It also requires par2 if you want fsck to be
76 able to generate the information needed to recover from some types
79 - It currently only works on Linux, FreeBSD, NetBSD, OS X >= 10.4,
80 Solaris, or Windows (with Cygwin, and maybe with WSL). Patches to
81 support other platforms are welcome.
83 - Any items in "Things that are stupid" below.
86 Notable changes introduced by a release
87 =======================================
89 - <a href="note/0.30-from-0.29.3.md">Changes in 0.30 as compared to 0.29.3</a>
90 - <a href="note/0.29.3-from-0.29.2.md">Changes in 0.29.3 as compared to 0.29.2</a>
91 - <a href="note/0.29.2-from-0.29.1.md">Changes in 0.29.2 as compared to 0.29.1</a>
92 - <a href="note/0.29.1-from-0.29.md">Changes in 0.29.1 as compared to 0.29</a>
93 - <a href="note/0.29-from-0.28.1.md">Changes in 0.29 as compared to 0.28.1</a>
94 - <a href="note/0.28.1-from-0.28.md">Changes in 0.28.1 as compared to 0.28</a>
95 - <a href="note/0.28-from-0.27.1.md">Changes in 0.28 as compared to 0.27.1</a>
96 - <a href="note/0.27.1-from-0.27.md">Changes in 0.27.1 as compared to 0.27</a>
102 | branch | Debian | FreeBSD | macOS |
103 |--------|------------------------------------------------------------------------------------------------------------------------------------------------|--------------------------------------------------------------------------------------------------------------------------------------------------|----------------------------------------------------------------------------------------------------------------------------------------------|
104 | master | [![Debian test status](https://api.cirrus-ci.com/github/bup/bup.svg?branch=master&task=debian)](https://cirrus-ci.com/github/bup/bup) | [![FreeBSD test status](https://api.cirrus-ci.com/github/bup/bup.svg?branch=master&task=freebsd)](https://cirrus-ci.com/github/bup/bup) | [![macOS test status](https://api.cirrus-ci.com/github/bup/bup.svg?branch=master&task=macos)](https://cirrus-ci.com/github/bup/bup) |
105 | 0.29.x | [![Debian test status](https://api.cirrus-ci.com/github/bup/bup.svg?branch=0.29.x&task=debian)](https://cirrus-ci.com/github/bup/bup) | [![FreeBSD test status](https://api.cirrus-ci.com/github/bup/bup.svg?branch=0.29.x&task=freebsd)](https://cirrus-ci.com/github/bup/bup) | [![macOS test status](https://api.cirrus-ci.com/github/bup/bup.svg?branch=0.29.x&task=macos)](https://cirrus-ci.com/github/bup/bup) |
113 - Check out the bup source code using git:
116 git clone https://github.com/bup/bup
119 - This will leave you on the master branch, which is perfect if you
120 would like to help with development, but if you'd just like to use
121 bup, please check out the latest stable release like this:
127 You can see the latest stable release here:
128 https://github.com/bup/bup/releases.
130 - Install the required python libraries (including the development
133 On very recent Debian/Ubuntu versions, this may be sufficient (run
137 apt-get build-dep bup
140 Otherwise try this (substitute python2.6-dev if you have an older
144 apt-get install python2.7-dev python-fuse
145 apt-get install python-pyxattr python-pylibacl
146 apt-get install linux-libc-dev
147 apt-get install acl attr
148 apt-get install python-tornado # optional
151 On CentOS (for CentOS 6, at least), this should be sufficient (run
155 yum groupinstall "Development Tools"
156 yum install python python-devel
157 yum install fuse-python pyxattr pylibacl
158 yum install perl-Time-HiRes
161 In addition to the default CentOS repositories, you may need to add
162 RPMForge (for fuse-python) and EPEL (for pyxattr and pylibacl).
164 On Cygwin, install python, make, rsync, and gcc4.
166 If you would like to use the optional bup web server on systems
167 without a tornado package, you may want to try this:
173 - Build the python module and symlinks:
185 or if you're in a bit more of a hurry:
191 The tests should pass. If they don't pass for you, stop here and
192 send an email to bup-list@googlegroups.com. Though if there are
193 symbolic links along the current working directory path, the tests
194 may fail. Running something like this before "make test" should
195 sidestep the problem:
201 - You can install bup via "make install", and override the default
202 destination with DESTDIR and PREFIX.
204 Files are normally installed to "$DESTDIR/$PREFIX" where DESTDIR is
205 empty by default, and PREFIX is set to /usr/local. So if you wanted to
206 install bup to /opt/bup, you might do something like this:
209 make install DESTDIR=/opt/bup PREFIX=''
212 - The Python executable that bup will use is chosen by ./configure,
213 which will search for a reasonable version unless PYTHON is set in
214 the environment, in which case, bup will use that path. You can
215 see which Python executable was chosen by looking at the
216 configure output, or examining cmd/python-cmd.sh, and you can
217 change the selection by re-running ./configure.
222 Binary packages of bup are known to be built for the following OSes:
225 http://packages.debian.org/search?searchon=names&keywords=bup
227 http://packages.ubuntu.com/search?searchon=names&keywords=bup
228 - pkgsrc (NetBSD, Dragonfly, and others)
229 http://pkgsrc.se/sysutils/bup
230 http://cvsweb.netbsd.org/bsdweb.cgi/pkgsrc/sysutils/bup/
232 https://www.archlinux.org/packages/?sort=&q=bup
234 https://apps.fedoraproject.org/packages/bup
240 - Get help for any bup command:
251 - Initialize the default BUP_DIR (~/.bup -- you can choose another by
252 either specifying `bup -d DIR ...` or setting the `BUP_DIR`
253 environment variable for a command):
259 - Make a local backup (-v or -vv will increase the verbosity):
263 bup save -n local-etc /etc
266 - Restore a local backup to ./dest:
269 bup restore -C ./dest local-etc/latest/etc
273 - Look at how much disk space your backup took:
279 - Make another backup (which should be mostly identical to the last one;
280 notice that you don't have to *specify* that this backup is incremental,
281 it just saves space automatically):
285 bup save -n local-etc /etc
288 - Look how little extra space your second backup used (on top of the first):
294 - Get a list of your previous backups:
300 - Restore your first backup again:
303 bup restore -C ./dest-2 local-etc/2013-11-23-11195/etc
306 - Make a backup to a remote server which must already have the 'bup' command
307 somewhere in its PATH (see /etc/profile, etc/environment, ~/.profile, or
308 ~/.bashrc), and be accessible via ssh.
309 Make sure to replace SERVERNAME with the actual hostname of your server:
312 bup init -r SERVERNAME:path/to/remote-bup-dir
314 bup save -r SERVERNAME:path/to/remote-bup-dir -n local-etc /etc
317 - Make a remote backup to ~/.bup on SERVER:
321 bup save -r SERVER: -n local-etc /etc
324 - See what saves are available in ~/.bup on SERVER:
330 - Restore the remote backup to ./dest:
333 bup restore -r SERVER: -C ./dest local-etc/latest/etc
337 - Defend your backups from death rays (OK fine, more likely from the
338 occasional bad disk block). This writes parity information
339 (currently via par2) for all of the existing data so that bup may
340 be able to recover from some amount of repository corruption:
346 - Use split/join instead of index/save/restore. Try making a local
350 tar -cvf - /etc | bup split -n local-etc -vv
353 - Try restoring the tarball:
356 bup join local-etc | tar -tf -
359 - Look at how much disk space your backup took:
365 - Make another tar backup:
368 tar -cvf - /etc | bup split -n local-etc -vv
371 - Look at how little extra space your second backup used on top of
378 - Restore the first tar backup again (the ~1 is git notation for "one
379 older than the most recent"):
382 bup join local-etc~1 | tar -tf -
385 - Get a list of your previous split-based backups:
388 GIT_DIR=~/.bup git log local-etc
391 - Save a tar archive to a remote server (without tar -z to facilitate
395 tar -cvf - /etc | bup split -r SERVERNAME: -n local-etc -vv
398 - Restore the archive:
401 bup join -r SERVERNAME: local-etc | tar -tf -
404 That's all there is to it!
410 - FreeBSD's default 'make' command doesn't like bup's Makefile. In order to
411 compile the code, run tests and install bup, you need to install GNU Make
412 from the port named 'gmake' and use its executable instead in the commands
413 seen above. (i.e. 'gmake test' runs bup's test suite)
415 - Python's development headers are automatically installed with the 'python'
416 port so there's no need to install them separately.
418 - To use the 'bup fuse' command, you need to install the fuse kernel module
419 from the 'fusefs-kmod' port in the 'sysutils' section and the libraries from
420 the port named 'py-fusefs' in the 'devel' section.
422 - The 'par2' command can be found in the port named 'par2cmdline'.
424 - In order to compile the documentation, you need pandoc which can be found in
425 the port named 'hs-pandoc' in the 'textproc' section.
428 Notes on NetBSD/pkgsrc
429 ----------------------
431 - See pkgsrc/sysutils/bup, which should be the most recent stable
432 release and includes man pages. It also has a reasonable set of
433 dependencies (git, par2, py-fuse-bindings).
435 - The "fuse-python" package referred to is hard to locate, and is a
436 separate tarball for the python language binding distributed by the
437 fuse project on sourceforge. It is available as
438 pkgsrc/filesystems/py-fuse-bindings and on NetBSD 5, "bup fuse"
441 - "bup fuse" presents every directory/file as inode 0. The directory
442 traversal code ("fts") in NetBSD's libc will interpret this as a
443 cycle and error out, so "ls -R" and "find" will not work.
445 - There is no support for ACLs. If/when some enterprising person
446 fixes this, adjust t/compare-trees.
452 - There is no support for ACLs. If/when some enterprising person
453 fixes this, adjust t/compare-trees.
455 - In t/test.sh, two tests have been disabled. These tests check to
456 see that repeated saves produce identical trees and that an
457 intervening index doesn't change the SHA1. Apparently Cygwin has
458 some unusual behaviors with respect to access times (that probably
459 warrant further investigation). Possibly related:
460 http://cygwin.com/ml/cygwin/2007-06/msg00436.html
466 - There is no support for ACLs. If/when some enterprising person
467 fixes this, adjust t/compare-trees.
476 bup stores its data in a git-formatted repository. Unfortunately, git
477 itself doesn't actually behave very well for bup's use case (huge numbers of
478 files, files with huge sizes, retaining file permissions/ownership are
479 important), so we mostly don't use git's *code* except for a few helper
480 programs. For example, bup has its own git packfile writer written in
483 Basically, 'bup split' reads the data on stdin (or from files specified on
484 the command line), breaks it into chunks using a rolling checksum (similar to
485 rsync), and saves those chunks into a new git packfile. There is at least one
486 git packfile per backup.
488 When deciding whether to write a particular chunk into the new packfile, bup
489 first checks all the other packfiles that exist to see if they already have that
490 chunk. If they do, the chunk is skipped.
492 git packs come in two parts: the pack itself (*.pack) and the index (*.idx).
493 The index is pretty small, and contains a list of all the objects in the
494 pack. Thus, when generating a remote backup, we don't have to have a copy
495 of the packfiles from the remote server: the local end just downloads a copy
496 of the server's *index* files, and compares objects against those when
497 generating the new pack, which it sends directly to the server.
499 The "-n" option to 'bup split' and 'bup save' is the name of the backup you
500 want to create, but it's actually implemented as a git branch. So you can
501 do cute things like checkout a particular branch using git, and receive a
502 bunch of chunk files corresponding to the file you split.
504 If you use '-b' or '-t' or '-c' instead of '-n', bup split will output a
505 list of blobs, a tree containing that list of blobs, or a commit containing
506 that tree, respectively, to stdout. You can use this to construct your own
507 scripts that do something with those values.
512 'bup index' walks through your filesystem and updates a file (whose name is,
513 by default, ~/.bup/bupindex) to contain the name, attributes, and an
514 optional git SHA1 (blob id) of each file and directory.
516 'bup save' basically just runs the equivalent of 'bup split' a whole bunch
517 of times, once per file in the index, and assembles a git tree
518 that contains all the resulting objects. Among other things, that makes
519 'git diff' much more useful (compared to splitting a tarball, which is
520 essentially a big binary blob). However, since bup splits large files into
521 smaller chunks, the resulting tree structure doesn't *exactly* correspond to
522 what git itself would have stored. Also, the tree format used by 'bup save'
523 will probably change in the future to support storing file ownership, more
524 complex file permissions, and so on.
526 If a file has previously been written by 'bup save', then its git blob/tree
527 id is stored in the index. This lets 'bup save' avoid reading that file to
528 produce future incremental backups, which means it can go *very* fast unless
529 a lot of files have changed.
532 Things that are stupid for now but which we'll fix later
533 ========================================================
535 Help with any of these problems, or others, is very welcome. Join the
536 mailing list (see below) if you'd like to help.
538 - 'bup save' and 'bup restore' have immature metadata support.
540 On the plus side, they actually do have support now, but it's new,
541 and not remotely as well tested as tar/rsync/whatever's. However,
542 you have to start somewhere, and as of 0.25, we think it's ready
543 for more general use. Please let us know if you have any trouble.
545 Also, if any strip or graft-style options are specified to 'bup
546 save', then no metadata will be written for the root directory.
547 That's obviously less than ideal.
549 - bup is overly optimistic about mmap. Right now bup just assumes
550 that it can mmap as large a block as it likes, and that mmap will
551 never fail. Yeah, right... If nothing else, this has failed on
552 32-bit architectures (and 31-bit is even worse -- looking at you,
555 To fix this, we might just implement a FakeMmap[1] class that uses
556 normal file IO and handles all of the mmap methods[2] that bup
557 actually calls. Then we'd swap in one of those whenever mmap
560 This would also require implementing some of the methods needed to
561 support "[]" array access, probably at a minimum __getitem__,
562 __setitem__, and __setslice__ [3].
564 [1] http://comments.gmane.org/gmane.comp.sysutils.backup.bup/613
565 [2] http://docs.python.org/2/library/mmap.html
566 [3] http://docs.python.org/2/reference/datamodel.html#emulating-container-types
568 - 'bup index' is slower than it should be.
570 It's still rather fast: it can iterate through all the filenames on my
571 600,000 file filesystem in a few seconds. But it still needs to rewrite
572 the entire index file just to add a single filename, which is pretty
573 nasty; it should just leave the new files in a second "extra index" file
576 - bup could use inotify for *really* efficient incremental backups.
578 You could even have your system doing "continuous" backups: whenever a
579 file changes, we immediately send an image of it to the server. We could
580 give the continuous-backup process a really low CPU and I/O priority so
581 you wouldn't even know it was running.
583 - bup only has experimental support for pruning old backups.
585 While you should now be able to drop old saves and branches with
586 `bup rm`, and reclaim the space occupied by data that's no longer
587 needed by other backups with `bup gc`, these commands are
588 experimental, and should be handled with great care. See the
589 man pages for more information.
591 Unless you want to help test the new commands, one possible
592 workaround is to just start a new BUP_DIR occasionally,
593 i.e. bup-2013, bup-2014...
595 - bup has never been tested on anything but Linux, FreeBSD, NetBSD,
596 OS X, and Windows+Cygwin.
598 There's nothing that makes it *inherently* non-portable, though, so
599 that's mostly a matter of someone putting in some effort. (For a
600 "native" Windows port, the most annoying thing is the absence of ssh in
601 a default Windows installation.)
603 - bup needs better documentation.
605 According to an article about bup in Linux Weekly News
606 (https://lwn.net/Articles/380983/), "it's a bit short on examples and
607 a user guide would be nice." Documentation is the sort of thing that
608 will never be great unless someone from outside contributes it (since
609 the developers can never remember which parts are hard to understand).
611 - bup is "relatively speedy" and has "pretty good" compression.
613 ...according to the same LWN article. Clearly neither of those is good
614 enough. We should have awe-inspiring speed and crazy-good compression.
615 Must work on that. Writing more parts in C might help with the speed.
619 Actually, that's not stupid, but you might consider it a
620 limitation. See the ["Related Projects"](https://bup.github.io/)
621 list for some possible options.
626 bup has an extensive set of man pages. Try using 'bup help' to get
627 started, or use 'bup help SUBCOMMAND' for any bup subcommand (like split,
628 join, index, save, etc.) to get details on that command.
630 For further technical details, please see ./DESIGN.
636 bup is a work in progress and there are many ways it can still be improved.
637 If you'd like to contribute patches, ideas, or bug reports, please join the
640 You can find the mailing list archives here:
642 http://groups.google.com/group/bup-list
644 and you can subscribe by sending a message to:
646 bup-list+subscribe@googlegroups.com
648 Please see <a href="HACKING">./HACKING</a> for
649 additional information, i.e. how to submit patches (hint - no pull
650 requests), how we handle branches, etc.