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 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/0.31-from-0.30.1.md">Changes in 0.31 as compared to 0.30.1</a>
94 - <a href="note/0.30.1-from-0.30.md">Changes in 0.30.1 as compared to 0.30</a>
95 - <a href="note/0.30-from-0.29.3.md">Changes in 0.30 as compared to 0.29.3</a>
96 - <a href="note/0.29.3-from-0.29.2.md">Changes in 0.29.3 as compared to 0.29.2</a>
97 - <a href="note/0.29.2-from-0.29.1.md">Changes in 0.29.2 as compared to 0.29.1</a>
98 - <a href="note/0.29.1-from-0.29.md">Changes in 0.29.1 as compared to 0.29</a>
99 - <a href="note/0.29-from-0.28.1.md">Changes in 0.29 as compared to 0.28.1</a>
100 - <a href="note/0.28.1-from-0.28.md">Changes in 0.28.1 as compared to 0.28</a>
101 - <a href="note/0.28-from-0.27.1.md">Changes in 0.28 as compared to 0.27.1</a>
102 - <a href="note/0.27.1-from-0.27.md">Changes in 0.27.1 as compared to 0.27</a>
108 | branch | Debian | FreeBSD | macOS |
109 |--------|------------------------------------------------------------------------------------------------------------------------------------------------|--------------------------------------------------------------------------------------------------------------------------------------------------|----------------------------------------------------------------------------------------------------------------------------------------------|
110 | master | [](https://cirrus-ci.com/github/bup/bup) | [](https://cirrus-ci.com/github/bup/bup) | [](https://cirrus-ci.com/github/bup/bup) |
111 | 0.30.x | [](https://cirrus-ci.com/github/bup/bup) | [](https://cirrus-ci.com/github/bup/bup) | [](https://cirrus-ci.com/github/bup/bup) |
112 | 0.29.x | [](https://cirrus-ci.com/github/bup/bup) | [](https://cirrus-ci.com/github/bup/bup) | [](https://cirrus-ci.com/github/bup/bup) |
120 - Check out the bup source code using git:
123 git clone https://github.com/bup/bup
126 - This will leave you on the master branch, which is perfect if you
127 would like to help with development, but if you'd just like to use
128 bup, please check out the latest stable release like this:
134 You can see the latest stable release here:
135 https://github.com/bup/bup/releases.
137 - Install the required python libraries (including the development
140 On very recent Debian/Ubuntu versions, this may be sufficient (run
144 apt-get build-dep bup
147 Otherwise try this (substitute python2.6-dev if you have an older
151 apt-get install python2.7-dev python-fuse
152 apt-get install python-pyxattr
153 apt-get install pkg-config linux-libc-dev libacl1-dev
154 apt-get install acl attr
155 apt-get isntall python-pytest-xdist # optional (parallel tests)
156 apt-get install libreadline-dev # optional (bup ftp)
157 apt-get install python-tornado # optional (bup web)
160 On CentOS (for CentOS 6, at least), this should be sufficient (run
164 yum groupinstall "Development Tools"
165 yum install python python-devel libacl-devel
166 yum install fuse-python pyxattr
167 yum install perl-Time-HiRes
168 yum install readline-devel # optional (bup ftp)
169 yum install python-tornado # optional (bup web)
172 In addition to the default CentOS repositories, you may need to add
173 RPMForge (for fuse-python) and EPEL (for pyxattr).
175 On Cygwin, install python, make, rsync, and gcc4.
177 If you would like to use the optional bup web server on systems
178 without a tornado package, you may want to try this:
184 - Build the python module and symlinks:
196 or if you're in a bit more of a hurry:
202 If you have the Python xdist module installed, then you can
203 probably run the tests faster by adding the make -j option (see <a
204 href="HACKING">./HACKING</a> for additional information):
210 The tests should pass. If they don't pass for you, stop here and
211 send an email to bup-list@googlegroups.com. Though if there are
212 symbolic links along the current working directory path, the tests
213 may fail. Running something like this before "make test" should
214 sidestep the problem:
220 - You can install bup via "make install", and override the default
221 destination with DESTDIR and PREFIX.
223 Files are normally installed to "$DESTDIR/$PREFIX" where DESTDIR is
224 empty by default, and PREFIX is set to /usr/local. So if you wanted to
225 install bup to /opt/bup, you might do something like this:
228 make install DESTDIR=/opt/bup PREFIX=''
231 - The Python executable that bup will use is chosen by ./configure,
232 which will search for a reasonable version unless PYTHON is set in
233 the environment, in which case, bup will use that path. You can
234 see which Python executable was chosen by looking at the
235 configure output, or examining cmd/python-cmd.sh, and you can
236 change the selection by re-running ./configure.
241 Binary packages of bup are known to be built for the following OSes:
244 http://packages.debian.org/search?searchon=names&keywords=bup
246 http://packages.ubuntu.com/search?searchon=names&keywords=bup
247 - pkgsrc (NetBSD, Dragonfly, and others)
248 http://pkgsrc.se/sysutils/bup
249 http://cvsweb.netbsd.org/bsdweb.cgi/pkgsrc/sysutils/bup/
251 https://www.archlinux.org/packages/?sort=&q=bup
253 https://apps.fedoraproject.org/packages/bup
255 https://formulae.brew.sh/formula/bup
261 - Get help for any bup command:
272 - Initialize the default BUP_DIR (~/.bup -- you can choose another by
273 either specifying `bup -d DIR ...` or setting the `BUP_DIR`
274 environment variable for a command):
280 - Make a local backup (-v or -vv will increase the verbosity):
284 bup save -n local-etc /etc
287 - Restore a local backup to ./dest:
290 bup restore -C ./dest local-etc/latest/etc
294 - Look at how much disk space your backup took:
300 - Make another backup (which should be mostly identical to the last one;
301 notice that you don't have to *specify* that this backup is incremental,
302 it just saves space automatically):
306 bup save -n local-etc /etc
309 - Look how little extra space your second backup used (on top of the first):
315 - Get a list of your previous backups:
321 - Restore your first backup again:
324 bup restore -C ./dest-2 local-etc/2013-11-23-11195/etc
327 - Make a backup to a remote server which must already have the 'bup' command
328 somewhere in its PATH (see /etc/profile, etc/environment, ~/.profile, or
329 ~/.bashrc), and be accessible via ssh.
330 Make sure to replace SERVERNAME with the actual hostname of your server:
333 bup init -r SERVERNAME:path/to/remote-bup-dir
335 bup save -r SERVERNAME:path/to/remote-bup-dir -n local-etc /etc
338 - Make a remote backup to ~/.bup on SERVER:
342 bup save -r SERVER: -n local-etc /etc
345 - See what saves are available in ~/.bup on SERVER:
351 - Restore the remote backup to ./dest:
354 bup restore -r SERVER: -C ./dest local-etc/latest/etc
358 - Defend your backups from death rays (OK fine, more likely from the
359 occasional bad disk block). This writes parity information
360 (currently via par2) for all of the existing data so that bup may
361 be able to recover from some amount of repository corruption:
367 - Use split/join instead of index/save/restore. Try making a local
371 tar -cvf - /etc | bup split -n local-etc -vv
374 - Try restoring the tarball:
377 bup join local-etc | tar -tf -
380 - Look at how much disk space your backup took:
386 - Make another tar backup:
389 tar -cvf - /etc | bup split -n local-etc -vv
392 - Look at how little extra space your second backup used on top of
399 - Restore the first tar backup again (the ~1 is git notation for "one
400 older than the most recent"):
403 bup join local-etc~1 | tar -tf -
406 - Get a list of your previous split-based backups:
409 GIT_DIR=~/.bup git log local-etc
412 - Save a tar archive to a remote server (without tar -z to facilitate
416 tar -cvf - /etc | bup split -r SERVERNAME: -n local-etc -vv
419 - Restore the archive:
422 bup join -r SERVERNAME: local-etc | tar -tf -
425 That's all there is to it!
431 - FreeBSD's default 'make' command doesn't like bup's Makefile. In order to
432 compile the code, run tests and install bup, you need to install GNU Make
433 from the port named 'gmake' and use its executable instead in the commands
434 seen above. (i.e. 'gmake test' runs bup's test suite)
436 - Python's development headers are automatically installed with the 'python'
437 port so there's no need to install them separately.
439 - To use the 'bup fuse' command, you need to install the fuse kernel module
440 from the 'fusefs-kmod' port in the 'sysutils' section and the libraries from
441 the port named 'py-fusefs' in the 'devel' section.
443 - The 'par2' command can be found in the port named 'par2cmdline'.
445 - In order to compile the documentation, you need pandoc which can be found in
446 the port named 'hs-pandoc' in the 'textproc' section.
449 Notes on NetBSD/pkgsrc
450 ----------------------
452 - See pkgsrc/sysutils/bup, which should be the most recent stable
453 release and includes man pages. It also has a reasonable set of
454 dependencies (git, par2, py-fuse-bindings).
456 - The "fuse-python" package referred to is hard to locate, and is a
457 separate tarball for the python language binding distributed by the
458 fuse project on sourceforge. It is available as
459 pkgsrc/filesystems/py-fuse-bindings and on NetBSD 5, "bup fuse"
462 - "bup fuse" presents every directory/file as inode 0. The directory
463 traversal code ("fts") in NetBSD's libc will interpret this as a
464 cycle and error out, so "ls -R" and "find" will not work.
466 - There is no support for ACLs. If/when some enterprising person
467 fixes this, adjust dev/compare-trees.
473 - There is no support for ACLs. If/when some enterprising person
474 fixes this, adjust dev/compare-trees.
476 - In test/ext/test-misc, two tests have been disabled. These tests
477 check to see that repeated saves produce identical trees and that
478 an intervening index doesn't change the SHA1. Apparently Cygwin
479 has some unusual behaviors with respect to access times (that
480 probably warrant further investigation). Possibly related:
481 http://cygwin.com/ml/cygwin/2007-06/msg00436.html
487 - There is no support for ACLs. If/when some enterprising person
488 fixes this, adjust dev/compare-trees.
497 bup stores its data in a git-formatted repository. Unfortunately, git
498 itself doesn't actually behave very well for bup's use case (huge numbers of
499 files, files with huge sizes, retaining file permissions/ownership are
500 important), so we mostly don't use git's *code* except for a few helper
501 programs. For example, bup has its own git packfile writer written in
504 Basically, 'bup split' reads the data on stdin (or from files specified on
505 the command line), breaks it into chunks using a rolling checksum (similar to
506 rsync), and saves those chunks into a new git packfile. There is at least one
507 git packfile per backup.
509 When deciding whether to write a particular chunk into the new packfile, bup
510 first checks all the other packfiles that exist to see if they already have that
511 chunk. If they do, the chunk is skipped.
513 git packs come in two parts: the pack itself (*.pack) and the index (*.idx).
514 The index is pretty small, and contains a list of all the objects in the
515 pack. Thus, when generating a remote backup, we don't have to have a copy
516 of the packfiles from the remote server: the local end just downloads a copy
517 of the server's *index* files, and compares objects against those when
518 generating the new pack, which it sends directly to the server.
520 The "-n" option to 'bup split' and 'bup save' is the name of the backup you
521 want to create, but it's actually implemented as a git branch. So you can
522 do cute things like checkout a particular branch using git, and receive a
523 bunch of chunk files corresponding to the file you split.
525 If you use '-b' or '-t' or '-c' instead of '-n', bup split will output a
526 list of blobs, a tree containing that list of blobs, or a commit containing
527 that tree, respectively, to stdout. You can use this to construct your own
528 scripts that do something with those values.
533 'bup index' walks through your filesystem and updates a file (whose name is,
534 by default, ~/.bup/bupindex) to contain the name, attributes, and an
535 optional git SHA1 (blob id) of each file and directory.
537 'bup save' basically just runs the equivalent of 'bup split' a whole bunch
538 of times, once per file in the index, and assembles a git tree
539 that contains all the resulting objects. Among other things, that makes
540 'git diff' much more useful (compared to splitting a tarball, which is
541 essentially a big binary blob). However, since bup splits large files into
542 smaller chunks, the resulting tree structure doesn't *exactly* correspond to
543 what git itself would have stored. Also, the tree format used by 'bup save'
544 will probably change in the future to support storing file ownership, more
545 complex file permissions, and so on.
547 If a file has previously been written by 'bup save', then its git blob/tree
548 id is stored in the index. This lets 'bup save' avoid reading that file to
549 produce future incremental backups, which means it can go *very* fast unless
550 a lot of files have changed.
553 Things that are stupid for now but which we'll fix later
554 ========================================================
556 Help with any of these problems, or others, is very welcome. Join the
557 mailing list (see below) if you'd like to help.
559 - 'bup save' and 'bup restore' have immature metadata support.
561 On the plus side, they actually do have support now, but it's new,
562 and not remotely as well tested as tar/rsync/whatever's. However,
563 you have to start somewhere, and as of 0.25, we think it's ready
564 for more general use. Please let us know if you have any trouble.
566 Also, if any strip or graft-style options are specified to 'bup
567 save', then no metadata will be written for the root directory.
568 That's obviously less than ideal.
570 - bup is overly optimistic about mmap. Right now bup just assumes
571 that it can mmap as large a block as it likes, and that mmap will
572 never fail. Yeah, right... If nothing else, this has failed on
573 32-bit architectures (and 31-bit is even worse -- looking at you,
576 To fix this, we might just implement a FakeMmap[1] class that uses
577 normal file IO and handles all of the mmap methods[2] that bup
578 actually calls. Then we'd swap in one of those whenever mmap
581 This would also require implementing some of the methods needed to
582 support "[]" array access, probably at a minimum __getitem__,
583 __setitem__, and __setslice__ [3].
585 [1] http://comments.gmane.org/gmane.comp.sysutils.backup.bup/613
586 [2] http://docs.python.org/2/library/mmap.html
587 [3] http://docs.python.org/2/reference/datamodel.html#emulating-container-types
589 - 'bup index' is slower than it should be.
591 It's still rather fast: it can iterate through all the filenames on my
592 600,000 file filesystem in a few seconds. But it still needs to rewrite
593 the entire index file just to add a single filename, which is pretty
594 nasty; it should just leave the new files in a second "extra index" file
597 - bup could use inotify for *really* efficient incremental backups.
599 You could even have your system doing "continuous" backups: whenever a
600 file changes, we immediately send an image of it to the server. We could
601 give the continuous-backup process a really low CPU and I/O priority so
602 you wouldn't even know it was running.
604 - bup only has experimental support for pruning old backups.
606 While you should now be able to drop old saves and branches with
607 `bup rm`, and reclaim the space occupied by data that's no longer
608 needed by other backups with `bup gc`, these commands are
609 experimental, and should be handled with great care. See the
610 man pages for more information.
612 Unless you want to help test the new commands, one possible
613 workaround is to just start a new BUP_DIR occasionally,
614 i.e. bup-2013, bup-2014...
616 - bup has never been tested on anything but Linux, FreeBSD, NetBSD,
617 OS X, and Windows+Cygwin.
619 There's nothing that makes it *inherently* non-portable, though, so
620 that's mostly a matter of someone putting in some effort. (For a
621 "native" Windows port, the most annoying thing is the absence of ssh in
622 a default Windows installation.)
624 - bup needs better documentation.
626 According to an article about bup in Linux Weekly News
627 (https://lwn.net/Articles/380983/), "it's a bit short on examples and
628 a user guide would be nice." Documentation is the sort of thing that
629 will never be great unless someone from outside contributes it (since
630 the developers can never remember which parts are hard to understand).
632 - bup is "relatively speedy" and has "pretty good" compression.
634 ...according to the same LWN article. Clearly neither of those is good
635 enough. We should have awe-inspiring speed and crazy-good compression.
636 Must work on that. Writing more parts in C might help with the speed.
640 Actually, that's not stupid, but you might consider it a
641 limitation. See the ["Related Projects"](https://bup.github.io/)
642 list for some possible options.
647 bup has an extensive set of man pages. Try using 'bup help' to get
648 started, or use 'bup help SUBCOMMAND' for any bup subcommand (like split,
649 join, index, save, etc.) to get details on that command.
651 For further technical details, please see ./DESIGN.
657 bup is a work in progress and there are many ways it can still be improved.
658 If you'd like to contribute patches, ideas, or bug reports, please join the
661 You can find the mailing list archives here:
663 http://groups.google.com/group/bup-list
665 and you can subscribe by sending a message to:
667 bup-list+subscribe@googlegroups.com
669 Please see <a href="HACKING">./HACKING</a> for
670 additional information, i.e. how to submit patches (hint - no pull
671 requests), how we handle branches, etc.
projects / bup.git / blob