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/0.29.2-from-0.29.1.md">Changes in 0.29.2 as compared to 0.29.1</a>
90 - <a href="note/0.29.1-from-0.29.md">Changes in 0.29.1 as compared to 0.29</a>
91 - <a href="note/0.29-from-0.28.1.md">Changes in 0.29 as compared to 0.28.1</a>
92 - <a href="note/0.28.1-from-0.28.md">Changes in 0.28.1 as compared to 0.28</a>
93 - <a href="note/0.28-from-0.27.1.md">Changes in 0.28 as compared to 0.27.1</a>
94 - <a href="note/0.27.1-from-0.27.md">Changes in 0.27.1 as compared to 0.27</a>
103 - Check out the bup source code using git:
105 git clone https://github.com/bup/bup
107 - This will leave you on the master branch, which is perfect if you
108 would like to help with development, but if you'd just like to use
109 bup, please check out the latest stable release like this:
113 You can see the latest stable release here:
114 https://github.com/bup/bup/releases.
116 - Install the required python libraries (including the development
119 On very recent Debian/Ubuntu versions, this may be sufficient (run
122 apt-get build-dep bup
124 Otherwise try this (substitute python2.6-dev if you have an older
127 apt-get install python2.7-dev python-fuse
128 apt-get install python-pyxattr python-pylibacl
129 apt-get install linux-libc-dev
130 apt-get install acl attr
131 apt-get install python-tornado # optional
133 On CentOS (for CentOS 6, at least), this should be sufficient (run
136 yum groupinstall "Development Tools"
137 yum install python python-devel
138 yum install fuse-python pyxattr pylibacl
139 yum install perl-Time-HiRes
141 In addition to the default CentOS repositories, you may need to add
142 RPMForge (for fuse-python) and EPEL (for pyxattr and pylibacl).
144 On Cygwin, install python, make, rsync, and gcc4.
146 If you would like to use the optional bup web server on systems
147 without a tornado package, you may want to try this:
151 - Build the python module and symlinks:
159 The tests should pass. If they don't pass for you, stop here and
160 send an email to bup-list@googlegroups.com. Though if there are
161 symbolic links along the current working directory path, the tests
162 may fail. Running something like this before "make test" should
163 sidestep the problem:
167 - You can install bup via "make install", and override the default
168 destination with DESTDIR and PREFIX.
170 Files are normally installed to "$DESTDIR/$PREFIX" where DESTDIR is
171 empty by default, and PREFIX is set to /usr/local. So if you wanted to
172 install bup to /opt/bup, you might do something like this:
174 make install DESTDIR=/opt/bup PREFIX=''
176 - The Python executable that bup will use is chosen by ./configure,
177 which will search for a reasonable version unless PYTHON is set in
178 the environment, in which case, bup will use that path. You can
179 see which Python executable was chosen by looking at the
180 configure output, or examining cmd/python-cmd.sh, and you can
181 change the selection by re-running ./configure.
186 Binary packages of bup are known to be built for the following OSes:
189 http://packages.debian.org/search?searchon=names&keywords=bup
191 http://packages.ubuntu.com/search?searchon=names&keywords=bup
192 - pkgsrc (NetBSD, Dragonfly, and others)
193 http://pkgsrc.se/sysutils/bup
194 http://cvsweb.netbsd.org/bsdweb.cgi/pkgsrc/sysutils/bup/
196 https://www.archlinux.org/packages/?sort=&q=bup
198 https://apps.fedoraproject.org/packages/bup
204 - Get help for any bup command:
213 - Initialize the default BUP_DIR (~/.bup -- you can choose another by
214 either specifying `bup -d DIR ...` or setting the `BUP_DIR`
215 environment variable for a command):
219 - Make a local backup (-v or -vv will increase the verbosity):
222 bup save -n local-etc /etc
224 - Restore a local backup to ./dest:
226 bup restore -C ./dest local-etc/latest/etc
229 - Look at how much disk space your backup took:
233 - Make another backup (which should be mostly identical to the last one;
234 notice that you don't have to *specify* that this backup is incremental,
235 it just saves space automatically):
238 bup save -n local-etc /etc
240 - Look how little extra space your second backup used (on top of the first):
244 - Get a list of your previous backups:
248 - Restore your first backup again:
250 bup restore -C ./dest-2 local-etc/2013-11-23-11195/etc
252 - Make a backup to a remote server which must already have the 'bup' command
253 somewhere in its PATH (see /etc/profile, etc/environment, ~/.profile, or
254 ~/.bashrc), and be accessible via ssh.
255 Make sure to replace SERVERNAME with the actual hostname of your server:
257 bup init -r SERVERNAME:path/to/remote-bup-dir
259 bup save -r SERVERNAME:path/to/remote-bup-dir -n local-etc /etc
261 - Make a remote backup to ~/.bup on SERVER:
264 bup save -r SERVER: -n local-etc /etc
266 - See what saves are available in ~/.bup on SERVER:
270 - Restore the remote backup to ./dest:
272 bup restore -r SERVER: -C ./dest local-etc/latest/etc
275 - Defend your backups from death rays (OK fine, more likely from the
276 occasional bad disk block). This writes parity information
277 (currently via par2) for all of the existing data so that bup may
278 be able to recover from some amount of repository corruption:
282 - Use split/join instead of index/save/restore. Try making a local
285 tar -cvf - /etc | bup split -n local-etc -vv
287 - Try restoring the tarball:
289 bup join local-etc | tar -tf -
291 - Look at how much disk space your backup took:
295 - Make another tar backup:
297 tar -cvf - /etc | bup split -n local-etc -vv
299 - Look at how little extra space your second backup used on top of
304 - Restore the first tar backup again (the ~1 is git notation for "one
305 older than the most recent"):
307 bup join local-etc~1 | tar -tf -
309 - Get a list of your previous split-based backups:
311 GIT_DIR=~/.bup git log local-etc
313 - Save a tar archive to a remote server (without tar -z to facilitate
316 tar -cvf - /etc | bup split -r SERVERNAME: -n local-etc -vv
318 - Restore the archive:
320 bup join -r SERVERNAME: local-etc | tar -tf -
322 That's all there is to it!
328 - FreeBSD's default 'make' command doesn't like bup's Makefile. In order to
329 compile the code, run tests and install bup, you need to install GNU Make
330 from the port named 'gmake' and use its executable instead in the commands
331 seen above. (i.e. 'gmake test' runs bup's test suite)
333 - Python's development headers are automatically installed with the 'python'
334 port so there's no need to install them separately.
336 - To use the 'bup fuse' command, you need to install the fuse kernel module
337 from the 'fusefs-kmod' port in the 'sysutils' section and the libraries from
338 the port named 'py-fusefs' in the 'devel' section.
340 - The 'par2' command can be found in the port named 'par2cmdline'.
342 - In order to compile the documentation, you need pandoc which can be found in
343 the port named 'hs-pandoc' in the 'textproc' section.
346 Notes on NetBSD/pkgsrc
347 ----------------------
349 - See pkgsrc/sysutils/bup, which should be the most recent stable
350 release and includes man pages. It also has a reasonable set of
351 dependencies (git, par2, py-fuse-bindings).
353 - The "fuse-python" package referred to is hard to locate, and is a
354 separate tarball for the python language binding distributed by the
355 fuse project on sourceforge. It is available as
356 pkgsrc/filesystems/py-fuse-bindings and on NetBSD 5, "bup fuse"
359 - "bup fuse" presents every directory/file as inode 0. The directory
360 traversal code ("fts") in NetBSD's libc will interpret this as a
361 cycle and error out, so "ls -R" and "find" will not work.
363 - There is no support for ACLs. If/when some entrprising person
364 fixes this, adjust t/compare-trees.
370 - There is no support for ACLs. If/when some enterprising person
371 fixes this, adjust t/compare-trees.
373 - In t/test.sh, two tests have been disabled. These tests check to
374 see that repeated saves produce identical trees and that an
375 intervening index doesn't change the SHA1. Apparently Cygwin has
376 some unusual behaviors with respect to access times (that probably
377 warrant further investigation). Possibly related:
378 http://cygwin.com/ml/cygwin/2007-06/msg00436.html
384 - There is no support for ACLs. If/when some enterprising person
385 fixes this, adjust t/compare-trees.
394 bup stores its data in a git-formatted repository. Unfortunately, git
395 itself doesn't actually behave very well for bup's use case (huge numbers of
396 files, files with huge sizes, retaining file permissions/ownership are
397 important), so we mostly don't use git's *code* except for a few helper
398 programs. For example, bup has its own git packfile writer written in
401 Basically, 'bup split' reads the data on stdin (or from files specified on
402 the command line), breaks it into chunks using a rolling checksum (similar to
403 rsync), and saves those chunks into a new git packfile. There is at least one
404 git packfile per backup.
406 When deciding whether to write a particular chunk into the new packfile, bup
407 first checks all the other packfiles that exist to see if they already have that
408 chunk. If they do, the chunk is skipped.
410 git packs come in two parts: the pack itself (*.pack) and the index (*.idx).
411 The index is pretty small, and contains a list of all the objects in the
412 pack. Thus, when generating a remote backup, we don't have to have a copy
413 of the packfiles from the remote server: the local end just downloads a copy
414 of the server's *index* files, and compares objects against those when
415 generating the new pack, which it sends directly to the server.
417 The "-n" option to 'bup split' and 'bup save' is the name of the backup you
418 want to create, but it's actually implemented as a git branch. So you can
419 do cute things like checkout a particular branch using git, and receive a
420 bunch of chunk files corresponding to the file you split.
422 If you use '-b' or '-t' or '-c' instead of '-n', bup split will output a
423 list of blobs, a tree containing that list of blobs, or a commit containing
424 that tree, respectively, to stdout. You can use this to construct your own
425 scripts that do something with those values.
430 'bup index' walks through your filesystem and updates a file (whose name is,
431 by default, ~/.bup/bupindex) to contain the name, attributes, and an
432 optional git SHA1 (blob id) of each file and directory.
434 'bup save' basically just runs the equivalent of 'bup split' a whole bunch
435 of times, once per file in the index, and assembles a git tree
436 that contains all the resulting objects. Among other things, that makes
437 'git diff' much more useful (compared to splitting a tarball, which is
438 essentially a big binary blob). However, since bup splits large files into
439 smaller chunks, the resulting tree structure doesn't *exactly* correspond to
440 what git itself would have stored. Also, the tree format used by 'bup save'
441 will probably change in the future to support storing file ownership, more
442 complex file permissions, and so on.
444 If a file has previously been written by 'bup save', then its git blob/tree
445 id is stored in the index. This lets 'bup save' avoid reading that file to
446 produce future incremental backups, which means it can go *very* fast unless
447 a lot of files have changed.
450 Things that are stupid for now but which we'll fix later
451 ========================================================
453 Help with any of these problems, or others, is very welcome. Join the
454 mailing list (see below) if you'd like to help.
456 - 'bup save' and 'bup restore' have immature metadata support.
458 On the plus side, they actually do have support now, but it's new,
459 and not remotely as well tested as tar/rsync/whatever's. However,
460 you have to start somewhere, and as of 0.25, we think it's ready
461 for more general use. Please let us know if you have any trouble.
463 Also, if any strip or graft-style options are specified to 'bup
464 save', then no metadata will be written for the root directory.
465 That's obviously less than ideal.
467 - bup is overly optimistic about mmap. Right now bup just assumes
468 that it can mmap as large a block as it likes, and that mmap will
469 never fail. Yeah, right... If nothing else, this has failed on
470 32-bit architectures (and 31-bit is even worse -- looking at you,
473 To fix this, we might just implement a FakeMmap[1] class that uses
474 normal file IO and handles all of the mmap methods[2] that bup
475 actually calls. Then we'd swap in one of those whenever mmap
478 This would also require implementing some of the methods needed to
479 support "[]" array access, probably at a minimum __getitem__,
480 __setitem__, and __setslice__ [3].
482 [1] http://comments.gmane.org/gmane.comp.sysutils.backup.bup/613
483 [2] http://docs.python.org/2/library/mmap.html
484 [3] http://docs.python.org/2/reference/datamodel.html#emulating-container-types
486 - 'bup index' is slower than it should be.
488 It's still rather fast: it can iterate through all the filenames on my
489 600,000 file filesystem in a few seconds. But it still needs to rewrite
490 the entire index file just to add a single filename, which is pretty
491 nasty; it should just leave the new files in a second "extra index" file
494 - bup could use inotify for *really* efficient incremental backups.
496 You could even have your system doing "continuous" backups: whenever a
497 file changes, we immediately send an image of it to the server. We could
498 give the continuous-backup process a really low CPU and I/O priority so
499 you wouldn't even know it was running.
501 - bup only has experimental support for pruning old backups.
503 While you should now be able to drop old saves and branches with
504 `bup rm`, and reclaim the space occupied by data that's no longer
505 needed by other backups with `bup gc`, these commands are
506 experimental, and should be handled with great care. See the
507 man pages for more information.
509 Unless you want to help test the new commands, one possible
510 workaround is to just start a new BUP_DIR occasionally,
511 i.e. bup-2013, bup-2014...
513 - bup has never been tested on anything but Linux, FreeBSD, NetBSD,
514 OS X, and Windows+Cygwin.
516 There's nothing that makes it *inherently* non-portable, though, so
517 that's mostly a matter of someone putting in some effort. (For a
518 "native" Windows port, the most annoying thing is the absence of ssh in
519 a default Windows installation.)
521 - bup needs better documentation.
523 According to an article about bup in Linux Weekly News
524 (https://lwn.net/Articles/380983/), "it's a bit short on examples and
525 a user guide would be nice." Documentation is the sort of thing that
526 will never be great unless someone from outside contributes it (since
527 the developers can never remember which parts are hard to understand).
529 - bup is "relatively speedy" and has "pretty good" compression.
531 ...according to the same LWN article. Clearly neither of those is good
532 enough. We should have awe-inspiring speed and crazy-good compression.
533 Must work on that. Writing more parts in C might help with the speed.
537 Actually, that's not stupid, but you might consider it a
538 limitation. See the ["Related Projects"](https://bup.github.io/)
539 list for some possible options.
544 bup has an extensive set of man pages. Try using 'bup help' to get
545 started, or use 'bup help SUBCOMMAND' for any bup subcommand (like split,
546 join, index, save, etc.) to get details on that command.
548 For further technical details, please see ./DESIGN.
554 bup is a work in progress and there are many ways it can still be improved.
555 If you'd like to contribute patches, ideas, or bug reports, please join the
558 You can find the mailing list archives here:
560 http://groups.google.com/group/bup-list
562 and you can subscribe by sending a message to:
564 bup-list+subscribe@googlegroups.com
566 Please see <a href="HACKING">./HACKING</a> for
567 additional information, i.e. how to submit patches (hint - no pull
568 requests), how we handle branches, etc.