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 3.7 or newer (or 2.7 for a bit longer), a C
75 compiler, and an installed git version >= 1.5.6. It also requires
76 par2 if you want fsck to be able to generate the information needed
77 to recover from some types of corruption. While python 2.7 is
78 still supported, please make plans to upgrade. Python 2 upstream
79 support ended on 2020-01-01, and we plan to drop support soon too.
81 - It currently only works on Linux, FreeBSD, NetBSD, OS X >= 10.4,
82 Solaris, or Windows (with Cygwin, and WSL). Patches to support
83 other platforms are welcome.
85 - Until resolved, a [glibc bug](https://sourceware.org/bugzilla/show_bug.cgi?id=26034)
86 might cause bup to crash on startup for some (unusual) command line
87 argument values, when bup is configured to use Python 3.
89 - Any items in "Things that are stupid" below.
91 Notable changes introduced by a release
92 =======================================
94 - <a href="note/0.31-from-0.30.1.md">Changes in 0.31 as compared to 0.30.1</a>
95 - <a href="note/0.30.1-from-0.30.md">Changes in 0.30.1 as compared to 0.30</a>
96 - <a href="note/0.30-from-0.29.3.md">Changes in 0.30 as compared to 0.29.3</a>
97 - <a href="note/0.29.3-from-0.29.2.md">Changes in 0.29.3 as compared to 0.29.2</a>
98 - <a href="note/0.29.2-from-0.29.1.md">Changes in 0.29.2 as compared to 0.29.1</a>
99 - <a href="note/0.29.1-from-0.29.md">Changes in 0.29.1 as compared to 0.29</a>
100 - <a href="note/0.29-from-0.28.1.md">Changes in 0.29 as compared to 0.28.1</a>
101 - <a href="note/0.28.1-from-0.28.md">Changes in 0.28.1 as compared to 0.28</a>
102 - <a href="note/0.28-from-0.27.1.md">Changes in 0.28 as compared to 0.27.1</a>
103 - <a href="note/0.27.1-from-0.27.md">Changes in 0.27.1 as compared to 0.27</a>
109 | branch | Debian | FreeBSD | macOS |
110 |--------|------------------------------------------------------------------------------------------------------------------------------------------------|--------------------------------------------------------------------------------------------------------------------------------------------------|----------------------------------------------------------------------------------------------------------------------------------------------|
111 | master | [](https://cirrus-ci.com/github/bup/bup) | [](https://cirrus-ci.com/github/bup/bup) | [](https://cirrus-ci.com/github/bup/bup) |
112 | 0.30.x | [](https://cirrus-ci.com/github/bup/bup) | [](https://cirrus-ci.com/github/bup/bup) | [](https://cirrus-ci.com/github/bup/bup) |
113 | 0.29.x | [](https://cirrus-ci.com/github/bup/bup) | [](https://cirrus-ci.com/github/bup/bup) | [](https://cirrus-ci.com/github/bup/bup) |
121 - Check out the bup source code using git:
124 git clone https://github.com/bup/bup
127 - This will leave you on the master branch, which is perfect if you
128 would like to help with development, but if you'd just like to use
129 bup, please check out the latest stable release like this:
135 You can see the latest stable release here:
136 https://github.com/bup/bup/releases.
138 - Install the required python libraries (including the development
141 On very recent Debian/Ubuntu versions, this may be sufficient (run
145 apt-get build-dep bup
151 apt-get install python3.7-dev python3-fuse
152 apt-get install python3-pyxattr python3-pytest
153 apt-get install python3-distutils
154 apt-get install pkg-config linux-libc-dev libacl1-dev
155 apt-get install gcc make acl attr rsync
156 apt-get isntall python3-pytest-xdist # optional (parallel tests)
157 apt-get install par2 # optional (error correction)
158 apt-get install libreadline-dev # optional (bup ftp)
159 apt-get install python3-tornado # optional (bup web)
162 Or, if you can't yet migrate to Python 3 (please try to soon):
165 apt-get install python2.7-dev python-fuse
166 apt-get install python-pyxattr python-pytest
167 apt-get install pkg-config linux-libc-dev libacl1-dev
168 apt-get install gcc make acl attr rsync
169 apt-get isntall python-pytest-xdist # optional (parallel tests)
170 apt-get install par2 # optional (error correction)
171 apt-get install libreadline-dev # optional (bup ftp)
172 apt-get install python-tornado # optional (bup web)
175 On CentOS (for CentOS 6, at least), this should be sufficient (run
179 yum groupinstall "Development Tools"
180 yum install python2 python2-devel libacl-devel pylibacl
181 yum install fuse-python pyxattr
182 yum install perl-Time-HiRes
183 yum install readline-devel # optional (bup ftp)
184 yum install python-tornado # optional (bup web)
187 In addition to the default CentOS repositories, you may need to add
188 RPMForge (for fuse-python) and EPEL (for pyxattr).
190 On Cygwin, install python, make, rsync, and gcc4.
192 If you would like to use the optional bup web server on systems
193 without a tornado package, you may want to try this:
199 - Build the python module and symlinks:
211 or if you're in a bit more of a hurry:
217 If you have the Python xdist module installed, then you can
218 probably run the tests faster by adding the make -j option (see <a
219 href="HACKING">./HACKING</a> for additional information):
225 The tests should pass. If they don't pass for you, stop here and
226 send an email to bup-list@googlegroups.com. Though if there are
227 symbolic links along the current working directory path, the tests
228 may fail. Running something like this before "make test" should
229 sidestep the problem:
235 - You can install bup via "make install", and override the default
236 destination with DESTDIR and PREFIX.
238 Files are normally installed to "$DESTDIR/$PREFIX" where DESTDIR is
239 empty by default, and PREFIX is set to /usr/local. So if you wanted to
240 install bup to /opt/bup, you might do something like this:
243 make install DESTDIR=/opt/bup PREFIX=''
246 - The Python executable that bup will use is chosen by ./configure,
247 which will search for a reasonable version unless PYTHON is set in
248 the environment, in which case, bup will use that path. You can
249 see which Python executable was chosen by looking at the
250 configure output, or examining cmd/python-cmd.sh, and you can
251 change the selection by re-running ./configure.
256 Binary packages of bup are known to be built for the following OSes:
259 http://packages.debian.org/search?searchon=names&keywords=bup
261 http://packages.ubuntu.com/search?searchon=names&keywords=bup
262 - pkgsrc (NetBSD, Dragonfly, and others)
263 http://pkgsrc.se/sysutils/bup
264 http://cvsweb.netbsd.org/bsdweb.cgi/pkgsrc/sysutils/bup/
266 https://www.archlinux.org/packages/?sort=&q=bup
268 https://apps.fedoraproject.org/packages/bup
270 https://formulae.brew.sh/formula/bup
276 - Get help for any bup command:
287 - Initialize the default BUP_DIR (~/.bup -- you can choose another by
288 either specifying `bup -d DIR ...` or setting the `BUP_DIR`
289 environment variable for a command):
295 - Make a local backup (-v or -vv will increase the verbosity):
299 bup save -n local-etc /etc
302 - Restore a local backup to ./dest:
305 bup restore -C ./dest local-etc/latest/etc
309 - Look at how much disk space your backup took:
315 - Make another backup (which should be mostly identical to the last one;
316 notice that you don't have to *specify* that this backup is incremental,
317 it just saves space automatically):
321 bup save -n local-etc /etc
324 - Look how little extra space your second backup used (on top of the first):
330 - Get a list of your previous backups:
336 - Restore your first backup again:
339 bup restore -C ./dest-2 local-etc/2013-11-23-11195/etc
342 - Make a backup to a remote server which must already have the 'bup' command
343 somewhere in its PATH (see /etc/profile, etc/environment, ~/.profile, or
344 ~/.bashrc), and be accessible via ssh.
345 Make sure to replace SERVERNAME with the actual hostname of your server:
348 bup init -r SERVERNAME:path/to/remote-bup-dir
350 bup save -r SERVERNAME:path/to/remote-bup-dir -n local-etc /etc
353 - Make a remote backup to ~/.bup on SERVER:
357 bup save -r SERVER: -n local-etc /etc
360 - See what saves are available in ~/.bup on SERVER:
366 - Restore the remote backup to ./dest:
369 bup restore -r SERVER: -C ./dest local-etc/latest/etc
373 - Defend your backups from death rays (OK fine, more likely from the
374 occasional bad disk block). This writes parity information
375 (currently via par2) for all of the existing data so that bup may
376 be able to recover from some amount of repository corruption:
382 - Use split/join instead of index/save/restore. Try making a local
386 tar -cvf - /etc | bup split -n local-etc -vv
389 - Try restoring the tarball:
392 bup join local-etc | tar -tf -
395 - Look at how much disk space your backup took:
401 - Make another tar backup:
404 tar -cvf - /etc | bup split -n local-etc -vv
407 - Look at how little extra space your second backup used on top of
414 - Restore the first tar backup again (the ~1 is git notation for "one
415 older than the most recent"):
418 bup join local-etc~1 | tar -tf -
421 - Get a list of your previous split-based backups:
424 GIT_DIR=~/.bup git log local-etc
427 - Save a tar archive to a remote server (without tar -z to facilitate
431 tar -cvf - /etc | bup split -r SERVERNAME: -n local-etc -vv
434 - Restore the archive:
437 bup join -r SERVERNAME: local-etc | tar -tf -
440 That's all there is to it!
446 - FreeBSD's default 'make' command doesn't like bup's Makefile. In order to
447 compile the code, run tests and install bup, you need to install GNU Make
448 from the port named 'gmake' and use its executable instead in the commands
449 seen above. (i.e. 'gmake test' runs bup's test suite)
451 - Python's development headers are automatically installed with the 'python'
452 port so there's no need to install them separately.
454 - To use the 'bup fuse' command, you need to install the fuse kernel module
455 from the 'fusefs-kmod' port in the 'sysutils' section and the libraries from
456 the port named 'py-fusefs' in the 'devel' section.
458 - The 'par2' command can be found in the port named 'par2cmdline'.
460 - In order to compile the documentation, you need pandoc which can be found in
461 the port named 'hs-pandoc' in the 'textproc' section.
464 Notes on NetBSD/pkgsrc
465 ----------------------
467 - See pkgsrc/sysutils/bup, which should be the most recent stable
468 release and includes man pages. It also has a reasonable set of
469 dependencies (git, par2, py-fuse-bindings).
471 - The "fuse-python" package referred to is hard to locate, and is a
472 separate tarball for the python language binding distributed by the
473 fuse project on sourceforge. It is available as
474 pkgsrc/filesystems/py-fuse-bindings and on NetBSD 5, "bup fuse"
477 - "bup fuse" presents every directory/file as inode 0. The directory
478 traversal code ("fts") in NetBSD's libc will interpret this as a
479 cycle and error out, so "ls -R" and "find" will not work.
481 - There is no support for ACLs. If/when some enterprising person
482 fixes this, adjust dev/compare-trees.
488 - There is no support for ACLs. If/when some enterprising person
489 fixes this, adjust dev/compare-trees.
491 - In test/ext/test-misc, two tests have been disabled. These tests
492 check to see that repeated saves produce identical trees and that
493 an intervening index doesn't change the SHA1. Apparently Cygwin
494 has some unusual behaviors with respect to access times (that
495 probably warrant further investigation). Possibly related:
496 http://cygwin.com/ml/cygwin/2007-06/msg00436.html
502 - There is no support for ACLs. If/when some enterprising person
503 fixes this, adjust dev/compare-trees.
512 bup stores its data in a git-formatted repository. Unfortunately, git
513 itself doesn't actually behave very well for bup's use case (huge numbers of
514 files, files with huge sizes, retaining file permissions/ownership are
515 important), so we mostly don't use git's *code* except for a few helper
516 programs. For example, bup has its own git packfile writer written in
519 Basically, 'bup split' reads the data on stdin (or from files specified on
520 the command line), breaks it into chunks using a rolling checksum (similar to
521 rsync), and saves those chunks into a new git packfile. There is at least one
522 git packfile per backup.
524 When deciding whether to write a particular chunk into the new packfile, bup
525 first checks all the other packfiles that exist to see if they already have that
526 chunk. If they do, the chunk is skipped.
528 git packs come in two parts: the pack itself (*.pack) and the index (*.idx).
529 The index is pretty small, and contains a list of all the objects in the
530 pack. Thus, when generating a remote backup, we don't have to have a copy
531 of the packfiles from the remote server: the local end just downloads a copy
532 of the server's *index* files, and compares objects against those when
533 generating the new pack, which it sends directly to the server.
535 The "-n" option to 'bup split' and 'bup save' is the name of the backup you
536 want to create, but it's actually implemented as a git branch. So you can
537 do cute things like checkout a particular branch using git, and receive a
538 bunch of chunk files corresponding to the file you split.
540 If you use '-b' or '-t' or '-c' instead of '-n', bup split will output a
541 list of blobs, a tree containing that list of blobs, or a commit containing
542 that tree, respectively, to stdout. You can use this to construct your own
543 scripts that do something with those values.
548 'bup index' walks through your filesystem and updates a file (whose name is,
549 by default, ~/.bup/bupindex) to contain the name, attributes, and an
550 optional git SHA1 (blob id) of each file and directory.
552 'bup save' basically just runs the equivalent of 'bup split' a whole bunch
553 of times, once per file in the index, and assembles a git tree
554 that contains all the resulting objects. Among other things, that makes
555 'git diff' much more useful (compared to splitting a tarball, which is
556 essentially a big binary blob). However, since bup splits large files into
557 smaller chunks, the resulting tree structure doesn't *exactly* correspond to
558 what git itself would have stored. Also, the tree format used by 'bup save'
559 will probably change in the future to support storing file ownership, more
560 complex file permissions, and so on.
562 If a file has previously been written by 'bup save', then its git blob/tree
563 id is stored in the index. This lets 'bup save' avoid reading that file to
564 produce future incremental backups, which means it can go *very* fast unless
565 a lot of files have changed.
568 Things that are stupid for now but which we'll fix later
569 ========================================================
571 Help with any of these problems, or others, is very welcome. Join the
572 mailing list (see below) if you'd like to help.
574 - 'bup save' and 'bup restore' have immature metadata support.
576 On the plus side, they actually do have support now, but it's new,
577 and not remotely as well tested as tar/rsync/whatever's. However,
578 you have to start somewhere, and as of 0.25, we think it's ready
579 for more general use. Please let us know if you have any trouble.
581 Also, if any strip or graft-style options are specified to 'bup
582 save', then no metadata will be written for the root directory.
583 That's obviously less than ideal.
585 - bup is overly optimistic about mmap. Right now bup just assumes
586 that it can mmap as large a block as it likes, and that mmap will
587 never fail. Yeah, right... If nothing else, this has failed on
588 32-bit architectures (and 31-bit is even worse -- looking at you,
591 To fix this, we might just implement a FakeMmap[1] class that uses
592 normal file IO and handles all of the mmap methods[2] that bup
593 actually calls. Then we'd swap in one of those whenever mmap
596 This would also require implementing some of the methods needed to
597 support "[]" array access, probably at a minimum __getitem__,
598 __setitem__, and __setslice__ [3].
600 [1] http://comments.gmane.org/gmane.comp.sysutils.backup.bup/613
601 [2] http://docs.python.org/2/library/mmap.html
602 [3] http://docs.python.org/2/reference/datamodel.html#emulating-container-types
604 - 'bup index' is slower than it should be.
606 It's still rather fast: it can iterate through all the filenames on my
607 600,000 file filesystem in a few seconds. But it still needs to rewrite
608 the entire index file just to add a single filename, which is pretty
609 nasty; it should just leave the new files in a second "extra index" file
612 - bup could use inotify for *really* efficient incremental backups.
614 You could even have your system doing "continuous" backups: whenever a
615 file changes, we immediately send an image of it to the server. We could
616 give the continuous-backup process a really low CPU and I/O priority so
617 you wouldn't even know it was running.
619 - bup only has experimental support for pruning old backups.
621 While you should now be able to drop old saves and branches with
622 `bup rm`, and reclaim the space occupied by data that's no longer
623 needed by other backups with `bup gc`, these commands are
624 experimental, and should be handled with great care. See the
625 man pages for more information.
627 Unless you want to help test the new commands, one possible
628 workaround is to just start a new BUP_DIR occasionally,
629 i.e. bup-2013, bup-2014...
631 - bup has never been tested on anything but Linux, FreeBSD, NetBSD,
632 OS X, and Windows+Cygwin.
634 There's nothing that makes it *inherently* non-portable, though, so
635 that's mostly a matter of someone putting in some effort. (For a
636 "native" Windows port, the most annoying thing is the absence of ssh in
637 a default Windows installation.)
639 - bup needs better documentation.
641 According to an article about bup in Linux Weekly News
642 (https://lwn.net/Articles/380983/), "it's a bit short on examples and
643 a user guide would be nice." Documentation is the sort of thing that
644 will never be great unless someone from outside contributes it (since
645 the developers can never remember which parts are hard to understand).
647 - bup is "relatively speedy" and has "pretty good" compression.
649 ...according to the same LWN article. Clearly neither of those is good
650 enough. We should have awe-inspiring speed and crazy-good compression.
651 Must work on that. Writing more parts in C might help with the speed.
655 Actually, that's not stupid, but you might consider it a
656 limitation. See the ["Related Projects"](https://bup.github.io/)
657 list for some possible options.
662 bup has an extensive set of man pages. Try using 'bup help' to get
663 started, or use 'bup help SUBCOMMAND' for any bup subcommand (like split,
664 join, index, save, etc.) to get details on that command.
666 For further technical details, please see ./DESIGN.
672 bup is a work in progress and there are many ways it can still be improved.
673 If you'd like to contribute patches, ideas, or bug reports, please join the
676 You can find the mailing list archives here:
678 http://groups.google.com/group/bup-list
680 and you can subscribe by sending a message to:
682 bup-list+subscribe@googlegroups.com
684 Please see <a href="HACKING">./HACKING</a> for
685 additional information, i.e. how to submit patches (hint - no pull
686 requests), how we handle branches, etc.
projects / bup.git / blob