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 | [](https://cirrus-ci.com/github/bup/bup) | [](https://cirrus-ci.com/github/bup/bup) | [](https://cirrus-ci.com/github/bup/bup) |
105 | 0.29.x | [](https://cirrus-ci.com/github/bup/bup) | [](https://cirrus-ci.com/github/bup/bup) | [](https://cirrus-ci.com/github/bup/bup) |
113 - Check out the bup source code using git:
115 git clone https://github.com/bup/bup
117 - This will leave you on the master branch, which is perfect if you
118 would like to help with development, but if you'd just like to use
119 bup, please check out the latest stable release like this:
123 You can see the latest stable release here:
124 https://github.com/bup/bup/releases.
126 - Install the required python libraries (including the development
129 On very recent Debian/Ubuntu versions, this may be sufficient (run
132 apt-get build-dep bup
134 Otherwise try this (substitute python2.6-dev if you have an older
137 apt-get install python2.7-dev python-fuse
138 apt-get install python-pyxattr python-pylibacl
139 apt-get install linux-libc-dev
140 apt-get install acl attr
141 apt-get install python-tornado # optional
143 On CentOS (for CentOS 6, at least), this should be sufficient (run
146 yum groupinstall "Development Tools"
147 yum install python python-devel
148 yum install fuse-python pyxattr pylibacl
149 yum install perl-Time-HiRes
151 In addition to the default CentOS repositories, you may need to add
152 RPMForge (for fuse-python) and EPEL (for pyxattr and pylibacl).
154 On Cygwin, install python, make, rsync, and gcc4.
156 If you would like to use the optional bup web server on systems
157 without a tornado package, you may want to try this:
161 - Build the python module and symlinks:
169 or if you're in a bit more of a hurry:
173 The tests should pass. If they don't pass for you, stop here and
174 send an email to bup-list@googlegroups.com. Though if there are
175 symbolic links along the current working directory path, the tests
176 may fail. Running something like this before "make test" should
177 sidestep the problem:
181 - You can install bup via "make install", and override the default
182 destination with DESTDIR and PREFIX.
184 Files are normally installed to "$DESTDIR/$PREFIX" where DESTDIR is
185 empty by default, and PREFIX is set to /usr/local. So if you wanted to
186 install bup to /opt/bup, you might do something like this:
188 make install DESTDIR=/opt/bup PREFIX=''
190 - The Python executable that bup will use is chosen by ./configure,
191 which will search for a reasonable version unless PYTHON is set in
192 the environment, in which case, bup will use that path. You can
193 see which Python executable was chosen by looking at the
194 configure output, or examining cmd/python-cmd.sh, and you can
195 change the selection by re-running ./configure.
200 Binary packages of bup are known to be built for the following OSes:
203 http://packages.debian.org/search?searchon=names&keywords=bup
205 http://packages.ubuntu.com/search?searchon=names&keywords=bup
206 - pkgsrc (NetBSD, Dragonfly, and others)
207 http://pkgsrc.se/sysutils/bup
208 http://cvsweb.netbsd.org/bsdweb.cgi/pkgsrc/sysutils/bup/
210 https://www.archlinux.org/packages/?sort=&q=bup
212 https://apps.fedoraproject.org/packages/bup
218 - Get help for any bup command:
227 - Initialize the default BUP_DIR (~/.bup -- you can choose another by
228 either specifying `bup -d DIR ...` or setting the `BUP_DIR`
229 environment variable for a command):
233 - Make a local backup (-v or -vv will increase the verbosity):
236 bup save -n local-etc /etc
238 - Restore a local backup to ./dest:
240 bup restore -C ./dest local-etc/latest/etc
243 - Look at how much disk space your backup took:
247 - Make another backup (which should be mostly identical to the last one;
248 notice that you don't have to *specify* that this backup is incremental,
249 it just saves space automatically):
252 bup save -n local-etc /etc
254 - Look how little extra space your second backup used (on top of the first):
258 - Get a list of your previous backups:
262 - Restore your first backup again:
264 bup restore -C ./dest-2 local-etc/2013-11-23-11195/etc
266 - Make a backup to a remote server which must already have the 'bup' command
267 somewhere in its PATH (see /etc/profile, etc/environment, ~/.profile, or
268 ~/.bashrc), and be accessible via ssh.
269 Make sure to replace SERVERNAME with the actual hostname of your server:
271 bup init -r SERVERNAME:path/to/remote-bup-dir
273 bup save -r SERVERNAME:path/to/remote-bup-dir -n local-etc /etc
275 - Make a remote backup to ~/.bup on SERVER:
278 bup save -r SERVER: -n local-etc /etc
280 - See what saves are available in ~/.bup on SERVER:
284 - Restore the remote backup to ./dest:
286 bup restore -r SERVER: -C ./dest local-etc/latest/etc
289 - Defend your backups from death rays (OK fine, more likely from the
290 occasional bad disk block). This writes parity information
291 (currently via par2) for all of the existing data so that bup may
292 be able to recover from some amount of repository corruption:
296 - Use split/join instead of index/save/restore. Try making a local
299 tar -cvf - /etc | bup split -n local-etc -vv
301 - Try restoring the tarball:
303 bup join local-etc | tar -tf -
305 - Look at how much disk space your backup took:
309 - Make another tar backup:
311 tar -cvf - /etc | bup split -n local-etc -vv
313 - Look at how little extra space your second backup used on top of
318 - Restore the first tar backup again (the ~1 is git notation for "one
319 older than the most recent"):
321 bup join local-etc~1 | tar -tf -
323 - Get a list of your previous split-based backups:
325 GIT_DIR=~/.bup git log local-etc
327 - Save a tar archive to a remote server (without tar -z to facilitate
330 tar -cvf - /etc | bup split -r SERVERNAME: -n local-etc -vv
332 - Restore the archive:
334 bup join -r SERVERNAME: local-etc | tar -tf -
336 That's all there is to it!
342 - FreeBSD's default 'make' command doesn't like bup's Makefile. In order to
343 compile the code, run tests and install bup, you need to install GNU Make
344 from the port named 'gmake' and use its executable instead in the commands
345 seen above. (i.e. 'gmake test' runs bup's test suite)
347 - Python's development headers are automatically installed with the 'python'
348 port so there's no need to install them separately.
350 - To use the 'bup fuse' command, you need to install the fuse kernel module
351 from the 'fusefs-kmod' port in the 'sysutils' section and the libraries from
352 the port named 'py-fusefs' in the 'devel' section.
354 - The 'par2' command can be found in the port named 'par2cmdline'.
356 - In order to compile the documentation, you need pandoc which can be found in
357 the port named 'hs-pandoc' in the 'textproc' section.
360 Notes on NetBSD/pkgsrc
361 ----------------------
363 - See pkgsrc/sysutils/bup, which should be the most recent stable
364 release and includes man pages. It also has a reasonable set of
365 dependencies (git, par2, py-fuse-bindings).
367 - The "fuse-python" package referred to is hard to locate, and is a
368 separate tarball for the python language binding distributed by the
369 fuse project on sourceforge. It is available as
370 pkgsrc/filesystems/py-fuse-bindings and on NetBSD 5, "bup fuse"
373 - "bup fuse" presents every directory/file as inode 0. The directory
374 traversal code ("fts") in NetBSD's libc will interpret this as a
375 cycle and error out, so "ls -R" and "find" will not work.
377 - There is no support for ACLs. If/when some entrprising person
378 fixes this, adjust t/compare-trees.
384 - There is no support for ACLs. If/when some enterprising person
385 fixes this, adjust t/compare-trees.
387 - In t/test.sh, two tests have been disabled. These tests check to
388 see that repeated saves produce identical trees and that an
389 intervening index doesn't change the SHA1. Apparently Cygwin has
390 some unusual behaviors with respect to access times (that probably
391 warrant further investigation). Possibly related:
392 http://cygwin.com/ml/cygwin/2007-06/msg00436.html
398 - There is no support for ACLs. If/when some enterprising person
399 fixes this, adjust t/compare-trees.
408 bup stores its data in a git-formatted repository. Unfortunately, git
409 itself doesn't actually behave very well for bup's use case (huge numbers of
410 files, files with huge sizes, retaining file permissions/ownership are
411 important), so we mostly don't use git's *code* except for a few helper
412 programs. For example, bup has its own git packfile writer written in
415 Basically, 'bup split' reads the data on stdin (or from files specified on
416 the command line), breaks it into chunks using a rolling checksum (similar to
417 rsync), and saves those chunks into a new git packfile. There is at least one
418 git packfile per backup.
420 When deciding whether to write a particular chunk into the new packfile, bup
421 first checks all the other packfiles that exist to see if they already have that
422 chunk. If they do, the chunk is skipped.
424 git packs come in two parts: the pack itself (*.pack) and the index (*.idx).
425 The index is pretty small, and contains a list of all the objects in the
426 pack. Thus, when generating a remote backup, we don't have to have a copy
427 of the packfiles from the remote server: the local end just downloads a copy
428 of the server's *index* files, and compares objects against those when
429 generating the new pack, which it sends directly to the server.
431 The "-n" option to 'bup split' and 'bup save' is the name of the backup you
432 want to create, but it's actually implemented as a git branch. So you can
433 do cute things like checkout a particular branch using git, and receive a
434 bunch of chunk files corresponding to the file you split.
436 If you use '-b' or '-t' or '-c' instead of '-n', bup split will output a
437 list of blobs, a tree containing that list of blobs, or a commit containing
438 that tree, respectively, to stdout. You can use this to construct your own
439 scripts that do something with those values.
444 'bup index' walks through your filesystem and updates a file (whose name is,
445 by default, ~/.bup/bupindex) to contain the name, attributes, and an
446 optional git SHA1 (blob id) of each file and directory.
448 'bup save' basically just runs the equivalent of 'bup split' a whole bunch
449 of times, once per file in the index, and assembles a git tree
450 that contains all the resulting objects. Among other things, that makes
451 'git diff' much more useful (compared to splitting a tarball, which is
452 essentially a big binary blob). However, since bup splits large files into
453 smaller chunks, the resulting tree structure doesn't *exactly* correspond to
454 what git itself would have stored. Also, the tree format used by 'bup save'
455 will probably change in the future to support storing file ownership, more
456 complex file permissions, and so on.
458 If a file has previously been written by 'bup save', then its git blob/tree
459 id is stored in the index. This lets 'bup save' avoid reading that file to
460 produce future incremental backups, which means it can go *very* fast unless
461 a lot of files have changed.
464 Things that are stupid for now but which we'll fix later
465 ========================================================
467 Help with any of these problems, or others, is very welcome. Join the
468 mailing list (see below) if you'd like to help.
470 - 'bup save' and 'bup restore' have immature metadata support.
472 On the plus side, they actually do have support now, but it's new,
473 and not remotely as well tested as tar/rsync/whatever's. However,
474 you have to start somewhere, and as of 0.25, we think it's ready
475 for more general use. Please let us know if you have any trouble.
477 Also, if any strip or graft-style options are specified to 'bup
478 save', then no metadata will be written for the root directory.
479 That's obviously less than ideal.
481 - bup is overly optimistic about mmap. Right now bup just assumes
482 that it can mmap as large a block as it likes, and that mmap will
483 never fail. Yeah, right... If nothing else, this has failed on
484 32-bit architectures (and 31-bit is even worse -- looking at you,
487 To fix this, we might just implement a FakeMmap[1] class that uses
488 normal file IO and handles all of the mmap methods[2] that bup
489 actually calls. Then we'd swap in one of those whenever mmap
492 This would also require implementing some of the methods needed to
493 support "[]" array access, probably at a minimum __getitem__,
494 __setitem__, and __setslice__ [3].
496 [1] http://comments.gmane.org/gmane.comp.sysutils.backup.bup/613
497 [2] http://docs.python.org/2/library/mmap.html
498 [3] http://docs.python.org/2/reference/datamodel.html#emulating-container-types
500 - 'bup index' is slower than it should be.
502 It's still rather fast: it can iterate through all the filenames on my
503 600,000 file filesystem in a few seconds. But it still needs to rewrite
504 the entire index file just to add a single filename, which is pretty
505 nasty; it should just leave the new files in a second "extra index" file
508 - bup could use inotify for *really* efficient incremental backups.
510 You could even have your system doing "continuous" backups: whenever a
511 file changes, we immediately send an image of it to the server. We could
512 give the continuous-backup process a really low CPU and I/O priority so
513 you wouldn't even know it was running.
515 - bup only has experimental support for pruning old backups.
517 While you should now be able to drop old saves and branches with
518 `bup rm`, and reclaim the space occupied by data that's no longer
519 needed by other backups with `bup gc`, these commands are
520 experimental, and should be handled with great care. See the
521 man pages for more information.
523 Unless you want to help test the new commands, one possible
524 workaround is to just start a new BUP_DIR occasionally,
525 i.e. bup-2013, bup-2014...
527 - bup has never been tested on anything but Linux, FreeBSD, NetBSD,
528 OS X, and Windows+Cygwin.
530 There's nothing that makes it *inherently* non-portable, though, so
531 that's mostly a matter of someone putting in some effort. (For a
532 "native" Windows port, the most annoying thing is the absence of ssh in
533 a default Windows installation.)
535 - bup needs better documentation.
537 According to an article about bup in Linux Weekly News
538 (https://lwn.net/Articles/380983/), "it's a bit short on examples and
539 a user guide would be nice." Documentation is the sort of thing that
540 will never be great unless someone from outside contributes it (since
541 the developers can never remember which parts are hard to understand).
543 - bup is "relatively speedy" and has "pretty good" compression.
545 ...according to the same LWN article. Clearly neither of those is good
546 enough. We should have awe-inspiring speed and crazy-good compression.
547 Must work on that. Writing more parts in C might help with the speed.
551 Actually, that's not stupid, but you might consider it a
552 limitation. See the ["Related Projects"](https://bup.github.io/)
553 list for some possible options.
558 bup has an extensive set of man pages. Try using 'bup help' to get
559 started, or use 'bup help SUBCOMMAND' for any bup subcommand (like split,
560 join, index, save, etc.) to get details on that command.
562 For further technical details, please see ./DESIGN.
568 bup is a work in progress and there are many ways it can still be improved.
569 If you'd like to contribute patches, ideas, or bug reports, please join the
572 You can find the mailing list archives here:
574 http://groups.google.com/group/bup-list
576 and you can subscribe by sending a message to:
578 bup-list+subscribe@googlegroups.com
580 Please see <a href="HACKING">./HACKING</a> for
581 additional information, i.e. how to submit patches (hint - no pull
582 requests), how we handle branches, etc.
projects / bup.git / blob