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, 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 WSL). Patches to support
81 other platforms are welcome.
83 - Until resolved, a [glibc bug](https://sourceware.org/bugzilla/show_bug.cgi?id=26034)
84 might cause bup to crash on startup for some (unusual) command line
85 argument values, when bup is configured to use Python 3.
87 - Any items in "Things that are stupid" below.
90 Notable changes introduced by a release
91 =======================================
93 - <a href="note/0.32-from-0.31.md">Changes in 0.32 as compared to 0.31</a>
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 | master | 0.30.x | 0.29.x |
110 |--------|--------|--------|
111 | [![master branch test status](https://api.cirrus-ci.com/github/bup/bup.svg?branch=master)](https://cirrus-ci.com/github/bup/bup) | [![0.30 branch test status](https://api.cirrus-ci.com/github/bup/bup.svg?branch=0.30.x)](https://cirrus-ci.com/github/bup/bup) | [![0.29 branch test status](https://api.cirrus-ci.com/github/bup/bup.svg?branch=0.29.x)](https://cirrus-ci.com/github/bup/bup) |
119 - Check out the bup source code using git:
122 git clone https://github.com/bup/bup
125 - This will leave you on the master branch, which is perfect if you
126 would like to help with development, but if you'd just like to use
127 bup, please check out the latest stable release like this:
133 You can see the latest stable release here:
134 https://github.com/bup/bup/releases.
136 - Install the required python libraries (including the development
139 On very recent Debian/Ubuntu versions, this may be sufficient (run
143 apt-get build-dep bup
149 apt-get install python3.7-dev python3-fuse
150 apt-get install python3-pyxattr python3-pytest
151 apt-get install python3-distutils
152 apt-get install pkg-config linux-libc-dev libacl1-dev
153 apt-get install gcc make acl attr rsync
154 apt-get isntall python3-pytest-xdist # optional (parallel tests)
155 apt-get install par2 # optional (error correction)
156 apt-get install libreadline-dev # optional (bup ftp)
157 apt-get install python3-tornado # optional (bup web)
161 On Cygwin, install python, make, rsync, and gcc4.
163 If you would like to use the optional bup web server on systems
164 without a tornado package, you may want to try this:
182 or if you're in a bit more of a hurry:
188 If you have the Python xdist module installed, then you can
189 probably run the tests faster by adding the make -j option (see <a
190 href="HACKING">./HACKING</a> for additional information):
196 The tests should pass. If they don't pass for you, stop here and
197 send an email to bup-list@googlegroups.com. Though if there are
198 symbolic links along the current working directory path, the tests
199 may fail. Running something like this before "make test" should
200 sidestep the problem:
206 - You can install bup via "make install", and override the default
207 destination with DESTDIR and PREFIX.
209 Files are normally installed to "$DESTDIR/$PREFIX" where DESTDIR is
210 empty by default, and PREFIX is set to /usr/local. So if you wanted to
211 install bup to /opt/bup, you might do something like this:
214 make install DESTDIR=/opt/bup PREFIX=''
217 - The Python version that bup will use is determined by the
218 `python-config` program chosen by `./configure`, which will search
219 for a reasonable version unless `BUP_PYTHON_CONFIG` is set in the
220 environment. You can see which Python executable was chosen by
221 looking at the configure output, or examining
222 `config/config.var/bup-python-config`, and you can change the
223 selection by re-running `./configure`.
228 Binary packages of bup are known to be built for the following OSes:
231 http://packages.debian.org/search?searchon=names&keywords=bup
233 http://packages.ubuntu.com/search?searchon=names&keywords=bup
234 - pkgsrc (NetBSD, Dragonfly, and others)
235 http://pkgsrc.se/sysutils/bup
236 http://cvsweb.netbsd.org/bsdweb.cgi/pkgsrc/sysutils/bup/
238 https://www.archlinux.org/packages/?sort=&q=bup
240 https://apps.fedoraproject.org/packages/bup
242 https://formulae.brew.sh/formula/bup
248 - Get help for any bup command:
259 - Initialize the default BUP_DIR (~/.bup -- you can choose another by
260 either specifying `bup -d DIR ...` or setting the `BUP_DIR`
261 environment variable for a command):
267 - Make a local backup (-v or -vv will increase the verbosity):
271 bup save -n local-etc /etc
274 - Restore a local backup to ./dest:
277 bup restore -C ./dest local-etc/latest/etc
281 - Look at how much disk space your backup took:
287 - Make another backup (which should be mostly identical to the last one;
288 notice that you don't have to *specify* that this backup is incremental,
289 it just saves space automatically):
293 bup save -n local-etc /etc
296 - Look how little extra space your second backup used (on top of the first):
302 - Get a list of your previous backups:
308 - Restore your first backup again:
311 bup restore -C ./dest-2 local-etc/2013-11-23-11195/etc
314 - Make a backup to a remote server which must already have the 'bup' command
315 somewhere in its PATH (see /etc/profile, etc/environment, ~/.profile, or
316 ~/.bashrc), and be accessible via ssh.
317 Make sure to replace SERVERNAME with the actual hostname of your server:
320 bup init -r SERVERNAME:path/to/remote-bup-dir
322 bup save -r SERVERNAME:path/to/remote-bup-dir -n local-etc /etc
325 - Make a remote backup to ~/.bup on SERVER:
329 bup save -r SERVER: -n local-etc /etc
332 - See what saves are available in ~/.bup on SERVER:
338 - Restore the remote backup to ./dest:
341 bup restore -r SERVER: -C ./dest local-etc/latest/etc
345 - Defend your backups from death rays (OK fine, more likely from the
346 occasional bad disk block). This writes parity information
347 (currently via par2) for all of the existing data so that bup may
348 be able to recover from some amount of repository corruption:
354 - Use split/join instead of index/save/restore. Try making a local
358 tar -cvf - /etc | bup split -n local-etc -vv
361 - Try restoring the tarball:
364 bup join local-etc | tar -tf -
367 - Look at how much disk space your backup took:
373 - Make another tar backup:
376 tar -cvf - /etc | bup split -n local-etc -vv
379 - Look at how little extra space your second backup used on top of
386 - Restore the first tar backup again (the ~1 is git notation for "one
387 older than the most recent"):
390 bup join local-etc~1 | tar -tf -
393 - Get a list of your previous split-based backups:
396 GIT_DIR=~/.bup git log local-etc
399 - Save a tar archive to a remote server (without tar -z to facilitate
403 tar -cvf - /etc | bup split -r SERVERNAME: -n local-etc -vv
406 - Restore the archive:
409 bup join -r SERVERNAME: local-etc | tar -tf -
412 That's all there is to it!
418 - FreeBSD's default 'make' command doesn't like bup's Makefile. In order to
419 compile the code, run tests and install bup, you need to install GNU Make
420 from the port named 'gmake' and use its executable instead in the commands
421 seen above. (i.e. 'gmake test' runs bup's test suite)
423 - Python's development headers are automatically installed with the 'python'
424 port so there's no need to install them separately.
426 - To use the 'bup fuse' command, you need to install the fuse kernel module
427 from the 'fusefs-kmod' port in the 'sysutils' section and the libraries from
428 the port named 'py-fusefs' in the 'devel' section.
430 - The 'par2' command can be found in the port named 'par2cmdline'.
432 - In order to compile the documentation, you need pandoc which can be found in
433 the port named 'hs-pandoc' in the 'textproc' section.
436 Notes on NetBSD/pkgsrc
437 ----------------------
439 - See pkgsrc/sysutils/bup, which should be the most recent stable
440 release and includes man pages. It also has a reasonable set of
441 dependencies (git, par2, py-fuse-bindings).
443 - The "fuse-python" package referred to is hard to locate, and is a
444 separate tarball for the python language binding distributed by the
445 fuse project on sourceforge. It is available as
446 pkgsrc/filesystems/py-fuse-bindings and on NetBSD 5, "bup fuse"
449 - "bup fuse" presents every directory/file as inode 0. The directory
450 traversal code ("fts") in NetBSD's libc will interpret this as a
451 cycle and error out, so "ls -R" and "find" will not work.
453 - There is no support for ACLs. If/when some enterprising person
454 fixes this, adjust dev/compare-trees.
460 - There is no support for ACLs. If/when some enterprising person
461 fixes this, adjust dev/compare-trees.
463 - In test/ext/test-misc, two tests have been disabled. These tests
464 check to see that repeated saves produce identical trees and that
465 an intervening index doesn't change the SHA1. Apparently Cygwin
466 has some unusual behaviors with respect to access times (that
467 probably warrant further investigation). Possibly related:
468 http://cygwin.com/ml/cygwin/2007-06/msg00436.html
474 - There is no support for ACLs. If/when some enterprising person
475 fixes this, adjust dev/compare-trees.
484 bup stores its data in a git-formatted repository. Unfortunately, git
485 itself doesn't actually behave very well for bup's use case (huge numbers of
486 files, files with huge sizes, retaining file permissions/ownership are
487 important), so we mostly don't use git's *code* except for a few helper
488 programs. For example, bup has its own git packfile writer written in
491 Basically, 'bup split' reads the data on stdin (or from files specified on
492 the command line), breaks it into chunks using a rolling checksum (similar to
493 rsync), and saves those chunks into a new git packfile. There is at least one
494 git packfile per backup.
496 When deciding whether to write a particular chunk into the new packfile, bup
497 first checks all the other packfiles that exist to see if they already have that
498 chunk. If they do, the chunk is skipped.
500 git packs come in two parts: the pack itself (*.pack) and the index (*.idx).
501 The index is pretty small, and contains a list of all the objects in the
502 pack. Thus, when generating a remote backup, we don't have to have a copy
503 of the packfiles from the remote server: the local end just downloads a copy
504 of the server's *index* files, and compares objects against those when
505 generating the new pack, which it sends directly to the server.
507 The "-n" option to 'bup split' and 'bup save' is the name of the backup you
508 want to create, but it's actually implemented as a git branch. So you can
509 do cute things like checkout a particular branch using git, and receive a
510 bunch of chunk files corresponding to the file you split.
512 If you use '-b' or '-t' or '-c' instead of '-n', bup split will output a
513 list of blobs, a tree containing that list of blobs, or a commit containing
514 that tree, respectively, to stdout. You can use this to construct your own
515 scripts that do something with those values.
520 'bup index' walks through your filesystem and updates a file (whose name is,
521 by default, ~/.bup/bupindex) to contain the name, attributes, and an
522 optional git SHA1 (blob id) of each file and directory.
524 'bup save' basically just runs the equivalent of 'bup split' a whole bunch
525 of times, once per file in the index, and assembles a git tree
526 that contains all the resulting objects. Among other things, that makes
527 'git diff' much more useful (compared to splitting a tarball, which is
528 essentially a big binary blob). However, since bup splits large files into
529 smaller chunks, the resulting tree structure doesn't *exactly* correspond to
530 what git itself would have stored. Also, the tree format used by 'bup save'
531 will probably change in the future to support storing file ownership, more
532 complex file permissions, and so on.
534 If a file has previously been written by 'bup save', then its git blob/tree
535 id is stored in the index. This lets 'bup save' avoid reading that file to
536 produce future incremental backups, which means it can go *very* fast unless
537 a lot of files have changed.
540 Things that are stupid for now but which we'll fix later
541 ========================================================
543 Help with any of these problems, or others, is very welcome. Join the
544 mailing list (see below) if you'd like to help.
546 - 'bup save' and 'bup restore' have immature metadata support.
548 On the plus side, they actually do have support now, but it's new,
549 and not remotely as well tested as tar/rsync/whatever's. However,
550 you have to start somewhere, and as of 0.25, we think it's ready
551 for more general use. Please let us know if you have any trouble.
553 Also, if any strip or graft-style options are specified to 'bup
554 save', then no metadata will be written for the root directory.
555 That's obviously less than ideal.
557 - bup is overly optimistic about mmap. Right now bup just assumes
558 that it can mmap as large a block as it likes, and that mmap will
559 never fail. Yeah, right... If nothing else, this has failed on
560 32-bit architectures (and 31-bit is even worse -- looking at you,
563 To fix this, we might just implement a FakeMmap[1] class that uses
564 normal file IO and handles all of the mmap methods[2] that bup
565 actually calls. Then we'd swap in one of those whenever mmap
568 This would also require implementing some of the methods needed to
569 support "[]" array access, probably at a minimum __getitem__,
570 __setitem__, and __setslice__ [3].
572 [1] http://comments.gmane.org/gmane.comp.sysutils.backup.bup/613
573 [2] http://docs.python.org/3/library/mmap.html
574 [3] http://docs.python.org/3/reference/datamodel.html#emulating-container-types
576 - 'bup index' is slower than it should be.
578 It's still rather fast: it can iterate through all the filenames on my
579 600,000 file filesystem in a few seconds. But it still needs to rewrite
580 the entire index file just to add a single filename, which is pretty
581 nasty; it should just leave the new files in a second "extra index" file
584 - bup could use inotify for *really* efficient incremental backups.
586 You could even have your system doing "continuous" backups: whenever a
587 file changes, we immediately send an image of it to the server. We could
588 give the continuous-backup process a really low CPU and I/O priority so
589 you wouldn't even know it was running.
591 - bup only has experimental support for pruning old backups.
593 While you should now be able to drop old saves and branches with
594 `bup rm`, and reclaim the space occupied by data that's no longer
595 needed by other backups with `bup gc`, these commands are
596 experimental, and should be handled with great care. See the
597 man pages for more information.
599 Unless you want to help test the new commands, one possible
600 workaround is to just start a new BUP_DIR occasionally,
601 i.e. bup-2013, bup-2014...
603 - bup has never been tested on anything but Linux, FreeBSD, NetBSD,
604 OS X, and Windows+Cygwin.
606 There's nothing that makes it *inherently* non-portable, though, so
607 that's mostly a matter of someone putting in some effort. (For a
608 "native" Windows port, the most annoying thing is the absence of ssh in
609 a default Windows installation.)
611 - bup needs better documentation.
613 According to an article about bup in Linux Weekly News
614 (https://lwn.net/Articles/380983/), "it's a bit short on examples and
615 a user guide would be nice." Documentation is the sort of thing that
616 will never be great unless someone from outside contributes it (since
617 the developers can never remember which parts are hard to understand).
619 - bup is "relatively speedy" and has "pretty good" compression.
621 ...according to the same LWN article. Clearly neither of those is good
622 enough. We should have awe-inspiring speed and crazy-good compression.
623 Must work on that. Writing more parts in C might help with the speed.
627 Actually, that's not stupid, but you might consider it a
628 limitation. See the ["Related Projects"](https://bup.github.io/)
629 list for some possible options.
634 bup has an extensive set of man pages. Try using 'bup help' to get
635 started, or use 'bup help SUBCOMMAND' for any bup subcommand (like split,
636 join, index, save, etc.) to get details on that command.
638 For further technical details, please see ./DESIGN.
644 bup is a work in progress and there are many ways it can still be improved.
645 If you'd like to contribute patches, ideas, or bug reports, please join the
646 <a href="mailto:bup-list@googlegroups.com">bup mailing list</a>:
648 You can find the mailing list archives here:
650 http://groups.google.com/group/bup-list
652 and you can subscribe by sending a message to:
654 bup-list+subscribe@googlegroups.com
656 You can also reach us via the
657 \#bup IRC channel at ircs://irc.libera.chat:6697/bup
658 on the [libera.chat](https://libera.chat/) network or via this
659 [web interface](https://web.libera.chat/?channels=bup).
661 Please see <a href="HACKING">./HACKING</a> for
662 additional information, i.e. how to submit patches (hint - no pull
663 requests), how we handle branches, etc.