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 - 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 install libreadline-dev # optional (bup ftp)
156 apt-get install python-tornado # optional (bup web)
159 On CentOS (for CentOS 6, at least), this should be sufficient (run
163 yum groupinstall "Development Tools"
164 yum install python python-devel libacl-devel
165 yum install fuse-python pyxattr
166 yum install perl-Time-HiRes
167 yum install readline-devel # optional (bup ftp)
168 yum install python-tornado # optional (bup web)
171 In addition to the default CentOS repositories, you may need to add
172 RPMForge (for fuse-python) and EPEL (for pyxattr).
174 On Cygwin, install python, make, rsync, and gcc4.
176 If you would like to use the optional bup web server on systems
177 without a tornado package, you may want to try this:
183 - Build the python module and symlinks:
195 or if you're in a bit more of a hurry:
201 The tests should pass. If they don't pass for you, stop here and
202 send an email to bup-list@googlegroups.com. Though if there are
203 symbolic links along the current working directory path, the tests
204 may fail. Running something like this before "make test" should
205 sidestep the problem:
211 - You can install bup via "make install", and override the default
212 destination with DESTDIR and PREFIX.
214 Files are normally installed to "$DESTDIR/$PREFIX" where DESTDIR is
215 empty by default, and PREFIX is set to /usr/local. So if you wanted to
216 install bup to /opt/bup, you might do something like this:
219 make install DESTDIR=/opt/bup PREFIX=''
222 - The Python executable that bup will use is chosen by ./configure,
223 which will search for a reasonable version unless PYTHON is set in
224 the environment, in which case, bup will use that path. You can
225 see which Python executable was chosen by looking at the
226 configure output, or examining cmd/python-cmd.sh, and you can
227 change the selection by re-running ./configure.
232 Binary packages of bup are known to be built for the following OSes:
235 http://packages.debian.org/search?searchon=names&keywords=bup
237 http://packages.ubuntu.com/search?searchon=names&keywords=bup
238 - pkgsrc (NetBSD, Dragonfly, and others)
239 http://pkgsrc.se/sysutils/bup
240 http://cvsweb.netbsd.org/bsdweb.cgi/pkgsrc/sysutils/bup/
242 https://www.archlinux.org/packages/?sort=&q=bup
244 https://apps.fedoraproject.org/packages/bup
250 - Get help for any bup command:
261 - Initialize the default BUP_DIR (~/.bup -- you can choose another by
262 either specifying `bup -d DIR ...` or setting the `BUP_DIR`
263 environment variable for a command):
269 - Make a local backup (-v or -vv will increase the verbosity):
273 bup save -n local-etc /etc
276 - Restore a local backup to ./dest:
279 bup restore -C ./dest local-etc/latest/etc
283 - Look at how much disk space your backup took:
289 - Make another backup (which should be mostly identical to the last one;
290 notice that you don't have to *specify* that this backup is incremental,
291 it just saves space automatically):
295 bup save -n local-etc /etc
298 - Look how little extra space your second backup used (on top of the first):
304 - Get a list of your previous backups:
310 - Restore your first backup again:
313 bup restore -C ./dest-2 local-etc/2013-11-23-11195/etc
316 - Make a backup to a remote server which must already have the 'bup' command
317 somewhere in its PATH (see /etc/profile, etc/environment, ~/.profile, or
318 ~/.bashrc), and be accessible via ssh.
319 Make sure to replace SERVERNAME with the actual hostname of your server:
322 bup init -r SERVERNAME:path/to/remote-bup-dir
324 bup save -r SERVERNAME:path/to/remote-bup-dir -n local-etc /etc
327 - Make a remote backup to ~/.bup on SERVER:
331 bup save -r SERVER: -n local-etc /etc
334 - See what saves are available in ~/.bup on SERVER:
340 - Restore the remote backup to ./dest:
343 bup restore -r SERVER: -C ./dest local-etc/latest/etc
347 - Defend your backups from death rays (OK fine, more likely from the
348 occasional bad disk block). This writes parity information
349 (currently via par2) for all of the existing data so that bup may
350 be able to recover from some amount of repository corruption:
356 - Use split/join instead of index/save/restore. Try making a local
360 tar -cvf - /etc | bup split -n local-etc -vv
363 - Try restoring the tarball:
366 bup join local-etc | tar -tf -
369 - Look at how much disk space your backup took:
375 - Make another tar backup:
378 tar -cvf - /etc | bup split -n local-etc -vv
381 - Look at how little extra space your second backup used on top of
388 - Restore the first tar backup again (the ~1 is git notation for "one
389 older than the most recent"):
392 bup join local-etc~1 | tar -tf -
395 - Get a list of your previous split-based backups:
398 GIT_DIR=~/.bup git log local-etc
401 - Save a tar archive to a remote server (without tar -z to facilitate
405 tar -cvf - /etc | bup split -r SERVERNAME: -n local-etc -vv
408 - Restore the archive:
411 bup join -r SERVERNAME: local-etc | tar -tf -
414 That's all there is to it!
420 - FreeBSD's default 'make' command doesn't like bup's Makefile. In order to
421 compile the code, run tests and install bup, you need to install GNU Make
422 from the port named 'gmake' and use its executable instead in the commands
423 seen above. (i.e. 'gmake test' runs bup's test suite)
425 - Python's development headers are automatically installed with the 'python'
426 port so there's no need to install them separately.
428 - To use the 'bup fuse' command, you need to install the fuse kernel module
429 from the 'fusefs-kmod' port in the 'sysutils' section and the libraries from
430 the port named 'py-fusefs' in the 'devel' section.
432 - The 'par2' command can be found in the port named 'par2cmdline'.
434 - In order to compile the documentation, you need pandoc which can be found in
435 the port named 'hs-pandoc' in the 'textproc' section.
438 Notes on NetBSD/pkgsrc
439 ----------------------
441 - See pkgsrc/sysutils/bup, which should be the most recent stable
442 release and includes man pages. It also has a reasonable set of
443 dependencies (git, par2, py-fuse-bindings).
445 - The "fuse-python" package referred to is hard to locate, and is a
446 separate tarball for the python language binding distributed by the
447 fuse project on sourceforge. It is available as
448 pkgsrc/filesystems/py-fuse-bindings and on NetBSD 5, "bup fuse"
451 - "bup fuse" presents every directory/file as inode 0. The directory
452 traversal code ("fts") in NetBSD's libc will interpret this as a
453 cycle and error out, so "ls -R" and "find" will not work.
455 - There is no support for ACLs. If/when some enterprising person
456 fixes this, adjust t/compare-trees.
462 - There is no support for ACLs. If/when some enterprising person
463 fixes this, adjust t/compare-trees.
465 - In t/test.sh, two tests have been disabled. These tests check to
466 see that repeated saves produce identical trees and that an
467 intervening index doesn't change the SHA1. Apparently Cygwin has
468 some unusual behaviors with respect to access times (that probably
469 warrant further investigation). Possibly related:
470 http://cygwin.com/ml/cygwin/2007-06/msg00436.html
476 - There is no support for ACLs. If/when some enterprising person
477 fixes this, adjust t/compare-trees.
486 bup stores its data in a git-formatted repository. Unfortunately, git
487 itself doesn't actually behave very well for bup's use case (huge numbers of
488 files, files with huge sizes, retaining file permissions/ownership are
489 important), so we mostly don't use git's *code* except for a few helper
490 programs. For example, bup has its own git packfile writer written in
493 Basically, 'bup split' reads the data on stdin (or from files specified on
494 the command line), breaks it into chunks using a rolling checksum (similar to
495 rsync), and saves those chunks into a new git packfile. There is at least one
496 git packfile per backup.
498 When deciding whether to write a particular chunk into the new packfile, bup
499 first checks all the other packfiles that exist to see if they already have that
500 chunk. If they do, the chunk is skipped.
502 git packs come in two parts: the pack itself (*.pack) and the index (*.idx).
503 The index is pretty small, and contains a list of all the objects in the
504 pack. Thus, when generating a remote backup, we don't have to have a copy
505 of the packfiles from the remote server: the local end just downloads a copy
506 of the server's *index* files, and compares objects against those when
507 generating the new pack, which it sends directly to the server.
509 The "-n" option to 'bup split' and 'bup save' is the name of the backup you
510 want to create, but it's actually implemented as a git branch. So you can
511 do cute things like checkout a particular branch using git, and receive a
512 bunch of chunk files corresponding to the file you split.
514 If you use '-b' or '-t' or '-c' instead of '-n', bup split will output a
515 list of blobs, a tree containing that list of blobs, or a commit containing
516 that tree, respectively, to stdout. You can use this to construct your own
517 scripts that do something with those values.
522 'bup index' walks through your filesystem and updates a file (whose name is,
523 by default, ~/.bup/bupindex) to contain the name, attributes, and an
524 optional git SHA1 (blob id) of each file and directory.
526 'bup save' basically just runs the equivalent of 'bup split' a whole bunch
527 of times, once per file in the index, and assembles a git tree
528 that contains all the resulting objects. Among other things, that makes
529 'git diff' much more useful (compared to splitting a tarball, which is
530 essentially a big binary blob). However, since bup splits large files into
531 smaller chunks, the resulting tree structure doesn't *exactly* correspond to
532 what git itself would have stored. Also, the tree format used by 'bup save'
533 will probably change in the future to support storing file ownership, more
534 complex file permissions, and so on.
536 If a file has previously been written by 'bup save', then its git blob/tree
537 id is stored in the index. This lets 'bup save' avoid reading that file to
538 produce future incremental backups, which means it can go *very* fast unless
539 a lot of files have changed.
542 Things that are stupid for now but which we'll fix later
543 ========================================================
545 Help with any of these problems, or others, is very welcome. Join the
546 mailing list (see below) if you'd like to help.
548 - 'bup save' and 'bup restore' have immature metadata support.
550 On the plus side, they actually do have support now, but it's new,
551 and not remotely as well tested as tar/rsync/whatever's. However,
552 you have to start somewhere, and as of 0.25, we think it's ready
553 for more general use. Please let us know if you have any trouble.
555 Also, if any strip or graft-style options are specified to 'bup
556 save', then no metadata will be written for the root directory.
557 That's obviously less than ideal.
559 - bup is overly optimistic about mmap. Right now bup just assumes
560 that it can mmap as large a block as it likes, and that mmap will
561 never fail. Yeah, right... If nothing else, this has failed on
562 32-bit architectures (and 31-bit is even worse -- looking at you,
565 To fix this, we might just implement a FakeMmap[1] class that uses
566 normal file IO and handles all of the mmap methods[2] that bup
567 actually calls. Then we'd swap in one of those whenever mmap
570 This would also require implementing some of the methods needed to
571 support "[]" array access, probably at a minimum __getitem__,
572 __setitem__, and __setslice__ [3].
574 [1] http://comments.gmane.org/gmane.comp.sysutils.backup.bup/613
575 [2] http://docs.python.org/2/library/mmap.html
576 [3] http://docs.python.org/2/reference/datamodel.html#emulating-container-types
578 - 'bup index' is slower than it should be.
580 It's still rather fast: it can iterate through all the filenames on my
581 600,000 file filesystem in a few seconds. But it still needs to rewrite
582 the entire index file just to add a single filename, which is pretty
583 nasty; it should just leave the new files in a second "extra index" file
586 - bup could use inotify for *really* efficient incremental backups.
588 You could even have your system doing "continuous" backups: whenever a
589 file changes, we immediately send an image of it to the server. We could
590 give the continuous-backup process a really low CPU and I/O priority so
591 you wouldn't even know it was running.
593 - bup only has experimental support for pruning old backups.
595 While you should now be able to drop old saves and branches with
596 `bup rm`, and reclaim the space occupied by data that's no longer
597 needed by other backups with `bup gc`, these commands are
598 experimental, and should be handled with great care. See the
599 man pages for more information.
601 Unless you want to help test the new commands, one possible
602 workaround is to just start a new BUP_DIR occasionally,
603 i.e. bup-2013, bup-2014...
605 - bup has never been tested on anything but Linux, FreeBSD, NetBSD,
606 OS X, and Windows+Cygwin.
608 There's nothing that makes it *inherently* non-portable, though, so
609 that's mostly a matter of someone putting in some effort. (For a
610 "native" Windows port, the most annoying thing is the absence of ssh in
611 a default Windows installation.)
613 - bup needs better documentation.
615 According to an article about bup in Linux Weekly News
616 (https://lwn.net/Articles/380983/), "it's a bit short on examples and
617 a user guide would be nice." Documentation is the sort of thing that
618 will never be great unless someone from outside contributes it (since
619 the developers can never remember which parts are hard to understand).
621 - bup is "relatively speedy" and has "pretty good" compression.
623 ...according to the same LWN article. Clearly neither of those is good
624 enough. We should have awe-inspiring speed and crazy-good compression.
625 Must work on that. Writing more parts in C might help with the speed.
629 Actually, that's not stupid, but you might consider it a
630 limitation. See the ["Related Projects"](https://bup.github.io/)
631 list for some possible options.
636 bup has an extensive set of man pages. Try using 'bup help' to get
637 started, or use 'bup help SUBCOMMAND' for any bup subcommand (like split,
638 join, index, save, etc.) to get details on that command.
640 For further technical details, please see ./DESIGN.
646 bup is a work in progress and there are many ways it can still be improved.
647 If you'd like to contribute patches, ideas, or bug reports, please join the
650 You can find the mailing list archives here:
652 http://groups.google.com/group/bup-list
654 and you can subscribe by sending a message to:
656 bup-list+subscribe@googlegroups.com
658 Please see <a href="HACKING">./HACKING</a> for
659 additional information, i.e. how to submit patches (hint - no pull
660 requests), how we handle branches, etc.
projects / bup.git / blob