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 (or 2.7 for a bit longer), a C
75 compiler, and an installed git version >= 1.5.6. It also requires
76 par2 if you want fsck to be able to generate the information needed
77 to recover from some types of corruption. While python 2.7 is
78 still supported, please make plans to upgrade. Python 2 upstream
79 support ended on 2020-01-01, and we plan to drop support soon too.
81 - It currently only works on Linux, FreeBSD, NetBSD, OS X >= 10.4,
82 Solaris, or Windows (with Cygwin, and WSL). Patches to support
83 other platforms are welcome.
85 - Until resolved, a [glibc bug](https://sourceware.org/bugzilla/show_bug.cgi?id=26034)
86 might cause bup to crash on startup for some (unusual) command line
87 argument values, when bup is configured to use Python 3.
89 - Any items in "Things that are stupid" below.
91 Notable changes introduced by a release
92 =======================================
94 - <a href="note/0.32-from-0.31.md">Changes in 0.32 as compared to 0.31</a>
95 - <a href="note/0.31-from-0.30.1.md">Changes in 0.31 as compared to 0.30.1</a>
96 - <a href="note/0.30.1-from-0.30.md">Changes in 0.30.1 as compared to 0.30</a>
97 - <a href="note/0.30-from-0.29.3.md">Changes in 0.30 as compared to 0.29.3</a>
98 - <a href="note/0.29.3-from-0.29.2.md">Changes in 0.29.3 as compared to 0.29.2</a>
99 - <a href="note/0.29.2-from-0.29.1.md">Changes in 0.29.2 as compared to 0.29.1</a>
100 - <a href="note/0.29.1-from-0.29.md">Changes in 0.29.1 as compared to 0.29</a>
101 - <a href="note/0.29-from-0.28.1.md">Changes in 0.29 as compared to 0.28.1</a>
102 - <a href="note/0.28.1-from-0.28.md">Changes in 0.28.1 as compared to 0.28</a>
103 - <a href="note/0.28-from-0.27.1.md">Changes in 0.28 as compared to 0.27.1</a>
104 - <a href="note/0.27.1-from-0.27.md">Changes in 0.27.1 as compared to 0.27</a>
110 | branch | Debian | FreeBSD | macOS |
111 |--------|------------------------------------------------------------------------------------------------------------------------------------------------|--------------------------------------------------------------------------------------------------------------------------------------------------|----------------------------------------------------------------------------------------------------------------------------------------------|
112 | master | [![Debian test status](https://api.cirrus-ci.com/github/bup/bup.svg?branch=master&task=debian)](https://cirrus-ci.com/github/bup/bup) | [![FreeBSD test status](https://api.cirrus-ci.com/github/bup/bup.svg?branch=master&task=freebsd)](https://cirrus-ci.com/github/bup/bup) | [![macOS test status](https://api.cirrus-ci.com/github/bup/bup.svg?branch=master&task=macos)](https://cirrus-ci.com/github/bup/bup) |
113 | 0.30.x | [![Debian test status](https://api.cirrus-ci.com/github/bup/bup.svg?branch=0.30.x&task=debian)](https://cirrus-ci.com/github/bup/bup) | [![FreeBSD test status](https://api.cirrus-ci.com/github/bup/bup.svg?branch=0.30.x&task=freebsd)](https://cirrus-ci.com/github/bup/bup) | [![macOS test status](https://api.cirrus-ci.com/github/bup/bup.svg?branch=0.30.x&task=macos)](https://cirrus-ci.com/github/bup/bup) |
114 | 0.29.x | [![Debian test status](https://api.cirrus-ci.com/github/bup/bup.svg?branch=0.29.x&task=debian)](https://cirrus-ci.com/github/bup/bup) | [![FreeBSD test status](https://api.cirrus-ci.com/github/bup/bup.svg?branch=0.29.x&task=freebsd)](https://cirrus-ci.com/github/bup/bup) | [![macOS test status](https://api.cirrus-ci.com/github/bup/bup.svg?branch=0.29.x&task=macos)](https://cirrus-ci.com/github/bup/bup) |
122 - Check out the bup source code using git:
125 git clone https://github.com/bup/bup
128 - This will leave you on the master branch, which is perfect if you
129 would like to help with development, but if you'd just like to use
130 bup, please check out the latest stable release like this:
136 You can see the latest stable release here:
137 https://github.com/bup/bup/releases.
139 - Install the required python libraries (including the development
142 On very recent Debian/Ubuntu versions, this may be sufficient (run
146 apt-get build-dep bup
152 apt-get install python3.7-dev python3-fuse
153 apt-get install python3-pyxattr python3-pytest
154 apt-get install python3-distutils
155 apt-get install pkg-config linux-libc-dev libacl1-dev
156 apt-get install gcc make acl attr rsync
157 apt-get isntall python3-pytest-xdist # optional (parallel tests)
158 apt-get install par2 # optional (error correction)
159 apt-get install libreadline-dev # optional (bup ftp)
160 apt-get install python3-tornado # optional (bup web)
163 Or, if you can't yet migrate to Python 3 (please try to soon):
166 apt-get install python2.7-dev python-fuse
167 apt-get install python-pyxattr python-pytest
168 apt-get install pkg-config linux-libc-dev libacl1-dev
169 apt-get install gcc make acl attr rsync
170 apt-get isntall python-pytest-xdist # optional (parallel tests)
171 apt-get install par2 # optional (error correction)
172 apt-get install libreadline-dev # optional (bup ftp)
173 apt-get install python-tornado # optional (bup web)
176 On CentOS (for CentOS 6, at least), this should be sufficient (run
180 yum groupinstall "Development Tools"
181 yum install python2 python2-devel libacl-devel pylibacl
182 yum install fuse-python pyxattr
183 yum install perl-Time-HiRes
184 yum install readline-devel # optional (bup ftp)
185 yum install python-tornado # optional (bup web)
188 In addition to the default CentOS repositories, you may need to add
189 RPMForge (for fuse-python) and EPEL (for pyxattr).
191 On Cygwin, install python, make, rsync, and gcc4.
193 If you would like to use the optional bup web server on systems
194 without a tornado package, you may want to try this:
212 or if you're in a bit more of a hurry:
218 If you have the Python xdist module installed, then you can
219 probably run the tests faster by adding the make -j option (see <a
220 href="HACKING">./HACKING</a> for additional information):
226 The tests should pass. If they don't pass for you, stop here and
227 send an email to bup-list@googlegroups.com. Though if there are
228 symbolic links along the current working directory path, the tests
229 may fail. Running something like this before "make test" should
230 sidestep the problem:
236 - You can install bup via "make install", and override the default
237 destination with DESTDIR and PREFIX.
239 Files are normally installed to "$DESTDIR/$PREFIX" where DESTDIR is
240 empty by default, and PREFIX is set to /usr/local. So if you wanted to
241 install bup to /opt/bup, you might do something like this:
244 make install DESTDIR=/opt/bup PREFIX=''
247 - The Python version that bup will use is determined by the
248 `python-config` program chosen by `./configure`, which will search
249 for a reasonable version unless `BUP_PYTHON_CONFIG` is set in the
250 environment. You can see which Python executable was chosen by
251 looking at the configure output, or examining
252 `config/config.var/bup-python-config`, and you can change the
253 selection by re-running `./configure`.
258 Binary packages of bup are known to be built for the following OSes:
261 http://packages.debian.org/search?searchon=names&keywords=bup
263 http://packages.ubuntu.com/search?searchon=names&keywords=bup
264 - pkgsrc (NetBSD, Dragonfly, and others)
265 http://pkgsrc.se/sysutils/bup
266 http://cvsweb.netbsd.org/bsdweb.cgi/pkgsrc/sysutils/bup/
268 https://www.archlinux.org/packages/?sort=&q=bup
270 https://apps.fedoraproject.org/packages/bup
272 https://formulae.brew.sh/formula/bup
278 - Get help for any bup command:
289 - Initialize the default BUP_DIR (~/.bup -- you can choose another by
290 either specifying `bup -d DIR ...` or setting the `BUP_DIR`
291 environment variable for a command):
297 - Make a local backup (-v or -vv will increase the verbosity):
301 bup save -n local-etc /etc
304 - Restore a local backup to ./dest:
307 bup restore -C ./dest local-etc/latest/etc
311 - Look at how much disk space your backup took:
317 - Make another backup (which should be mostly identical to the last one;
318 notice that you don't have to *specify* that this backup is incremental,
319 it just saves space automatically):
323 bup save -n local-etc /etc
326 - Look how little extra space your second backup used (on top of the first):
332 - Get a list of your previous backups:
338 - Restore your first backup again:
341 bup restore -C ./dest-2 local-etc/2013-11-23-11195/etc
344 - Make a backup to a remote server which must already have the 'bup' command
345 somewhere in its PATH (see /etc/profile, etc/environment, ~/.profile, or
346 ~/.bashrc), and be accessible via ssh.
347 Make sure to replace SERVERNAME with the actual hostname of your server:
350 bup init -r SERVERNAME:path/to/remote-bup-dir
352 bup save -r SERVERNAME:path/to/remote-bup-dir -n local-etc /etc
355 - Make a remote backup to ~/.bup on SERVER:
359 bup save -r SERVER: -n local-etc /etc
362 - See what saves are available in ~/.bup on SERVER:
368 - Restore the remote backup to ./dest:
371 bup restore -r SERVER: -C ./dest local-etc/latest/etc
375 - Defend your backups from death rays (OK fine, more likely from the
376 occasional bad disk block). This writes parity information
377 (currently via par2) for all of the existing data so that bup may
378 be able to recover from some amount of repository corruption:
384 - Use split/join instead of index/save/restore. Try making a local
388 tar -cvf - /etc | bup split -n local-etc -vv
391 - Try restoring the tarball:
394 bup join local-etc | tar -tf -
397 - Look at how much disk space your backup took:
403 - Make another tar backup:
406 tar -cvf - /etc | bup split -n local-etc -vv
409 - Look at how little extra space your second backup used on top of
416 - Restore the first tar backup again (the ~1 is git notation for "one
417 older than the most recent"):
420 bup join local-etc~1 | tar -tf -
423 - Get a list of your previous split-based backups:
426 GIT_DIR=~/.bup git log local-etc
429 - Save a tar archive to a remote server (without tar -z to facilitate
433 tar -cvf - /etc | bup split -r SERVERNAME: -n local-etc -vv
436 - Restore the archive:
439 bup join -r SERVERNAME: local-etc | tar -tf -
442 That's all there is to it!
448 - FreeBSD's default 'make' command doesn't like bup's Makefile. In order to
449 compile the code, run tests and install bup, you need to install GNU Make
450 from the port named 'gmake' and use its executable instead in the commands
451 seen above. (i.e. 'gmake test' runs bup's test suite)
453 - Python's development headers are automatically installed with the 'python'
454 port so there's no need to install them separately.
456 - To use the 'bup fuse' command, you need to install the fuse kernel module
457 from the 'fusefs-kmod' port in the 'sysutils' section and the libraries from
458 the port named 'py-fusefs' in the 'devel' section.
460 - The 'par2' command can be found in the port named 'par2cmdline'.
462 - In order to compile the documentation, you need pandoc which can be found in
463 the port named 'hs-pandoc' in the 'textproc' section.
466 Notes on NetBSD/pkgsrc
467 ----------------------
469 - See pkgsrc/sysutils/bup, which should be the most recent stable
470 release and includes man pages. It also has a reasonable set of
471 dependencies (git, par2, py-fuse-bindings).
473 - The "fuse-python" package referred to is hard to locate, and is a
474 separate tarball for the python language binding distributed by the
475 fuse project on sourceforge. It is available as
476 pkgsrc/filesystems/py-fuse-bindings and on NetBSD 5, "bup fuse"
479 - "bup fuse" presents every directory/file as inode 0. The directory
480 traversal code ("fts") in NetBSD's libc will interpret this as a
481 cycle and error out, so "ls -R" and "find" will not work.
483 - There is no support for ACLs. If/when some enterprising person
484 fixes this, adjust dev/compare-trees.
490 - There is no support for ACLs. If/when some enterprising person
491 fixes this, adjust dev/compare-trees.
493 - In test/ext/test-misc, two tests have been disabled. These tests
494 check to see that repeated saves produce identical trees and that
495 an intervening index doesn't change the SHA1. Apparently Cygwin
496 has some unusual behaviors with respect to access times (that
497 probably warrant further investigation). Possibly related:
498 http://cygwin.com/ml/cygwin/2007-06/msg00436.html
504 - There is no support for ACLs. If/when some enterprising person
505 fixes this, adjust dev/compare-trees.
514 bup stores its data in a git-formatted repository. Unfortunately, git
515 itself doesn't actually behave very well for bup's use case (huge numbers of
516 files, files with huge sizes, retaining file permissions/ownership are
517 important), so we mostly don't use git's *code* except for a few helper
518 programs. For example, bup has its own git packfile writer written in
521 Basically, 'bup split' reads the data on stdin (or from files specified on
522 the command line), breaks it into chunks using a rolling checksum (similar to
523 rsync), and saves those chunks into a new git packfile. There is at least one
524 git packfile per backup.
526 When deciding whether to write a particular chunk into the new packfile, bup
527 first checks all the other packfiles that exist to see if they already have that
528 chunk. If they do, the chunk is skipped.
530 git packs come in two parts: the pack itself (*.pack) and the index (*.idx).
531 The index is pretty small, and contains a list of all the objects in the
532 pack. Thus, when generating a remote backup, we don't have to have a copy
533 of the packfiles from the remote server: the local end just downloads a copy
534 of the server's *index* files, and compares objects against those when
535 generating the new pack, which it sends directly to the server.
537 The "-n" option to 'bup split' and 'bup save' is the name of the backup you
538 want to create, but it's actually implemented as a git branch. So you can
539 do cute things like checkout a particular branch using git, and receive a
540 bunch of chunk files corresponding to the file you split.
542 If you use '-b' or '-t' or '-c' instead of '-n', bup split will output a
543 list of blobs, a tree containing that list of blobs, or a commit containing
544 that tree, respectively, to stdout. You can use this to construct your own
545 scripts that do something with those values.
550 'bup index' walks through your filesystem and updates a file (whose name is,
551 by default, ~/.bup/bupindex) to contain the name, attributes, and an
552 optional git SHA1 (blob id) of each file and directory.
554 'bup save' basically just runs the equivalent of 'bup split' a whole bunch
555 of times, once per file in the index, and assembles a git tree
556 that contains all the resulting objects. Among other things, that makes
557 'git diff' much more useful (compared to splitting a tarball, which is
558 essentially a big binary blob). However, since bup splits large files into
559 smaller chunks, the resulting tree structure doesn't *exactly* correspond to
560 what git itself would have stored. Also, the tree format used by 'bup save'
561 will probably change in the future to support storing file ownership, more
562 complex file permissions, and so on.
564 If a file has previously been written by 'bup save', then its git blob/tree
565 id is stored in the index. This lets 'bup save' avoid reading that file to
566 produce future incremental backups, which means it can go *very* fast unless
567 a lot of files have changed.
570 Things that are stupid for now but which we'll fix later
571 ========================================================
573 Help with any of these problems, or others, is very welcome. Join the
574 mailing list (see below) if you'd like to help.
576 - 'bup save' and 'bup restore' have immature metadata support.
578 On the plus side, they actually do have support now, but it's new,
579 and not remotely as well tested as tar/rsync/whatever's. However,
580 you have to start somewhere, and as of 0.25, we think it's ready
581 for more general use. Please let us know if you have any trouble.
583 Also, if any strip or graft-style options are specified to 'bup
584 save', then no metadata will be written for the root directory.
585 That's obviously less than ideal.
587 - bup is overly optimistic about mmap. Right now bup just assumes
588 that it can mmap as large a block as it likes, and that mmap will
589 never fail. Yeah, right... If nothing else, this has failed on
590 32-bit architectures (and 31-bit is even worse -- looking at you,
593 To fix this, we might just implement a FakeMmap[1] class that uses
594 normal file IO and handles all of the mmap methods[2] that bup
595 actually calls. Then we'd swap in one of those whenever mmap
598 This would also require implementing some of the methods needed to
599 support "[]" array access, probably at a minimum __getitem__,
600 __setitem__, and __setslice__ [3].
602 [1] http://comments.gmane.org/gmane.comp.sysutils.backup.bup/613
603 [2] http://docs.python.org/2/library/mmap.html
604 [3] http://docs.python.org/2/reference/datamodel.html#emulating-container-types
606 - 'bup index' is slower than it should be.
608 It's still rather fast: it can iterate through all the filenames on my
609 600,000 file filesystem in a few seconds. But it still needs to rewrite
610 the entire index file just to add a single filename, which is pretty
611 nasty; it should just leave the new files in a second "extra index" file
614 - bup could use inotify for *really* efficient incremental backups.
616 You could even have your system doing "continuous" backups: whenever a
617 file changes, we immediately send an image of it to the server. We could
618 give the continuous-backup process a really low CPU and I/O priority so
619 you wouldn't even know it was running.
621 - bup only has experimental support for pruning old backups.
623 While you should now be able to drop old saves and branches with
624 `bup rm`, and reclaim the space occupied by data that's no longer
625 needed by other backups with `bup gc`, these commands are
626 experimental, and should be handled with great care. See the
627 man pages for more information.
629 Unless you want to help test the new commands, one possible
630 workaround is to just start a new BUP_DIR occasionally,
631 i.e. bup-2013, bup-2014...
633 - bup has never been tested on anything but Linux, FreeBSD, NetBSD,
634 OS X, and Windows+Cygwin.
636 There's nothing that makes it *inherently* non-portable, though, so
637 that's mostly a matter of someone putting in some effort. (For a
638 "native" Windows port, the most annoying thing is the absence of ssh in
639 a default Windows installation.)
641 - bup needs better documentation.
643 According to an article about bup in Linux Weekly News
644 (https://lwn.net/Articles/380983/), "it's a bit short on examples and
645 a user guide would be nice." Documentation is the sort of thing that
646 will never be great unless someone from outside contributes it (since
647 the developers can never remember which parts are hard to understand).
649 - bup is "relatively speedy" and has "pretty good" compression.
651 ...according to the same LWN article. Clearly neither of those is good
652 enough. We should have awe-inspiring speed and crazy-good compression.
653 Must work on that. Writing more parts in C might help with the speed.
657 Actually, that's not stupid, but you might consider it a
658 limitation. See the ["Related Projects"](https://bup.github.io/)
659 list for some possible options.
664 bup has an extensive set of man pages. Try using 'bup help' to get
665 started, or use 'bup help SUBCOMMAND' for any bup subcommand (like split,
666 join, index, save, etc.) to get details on that command.
668 For further technical details, please see ./DESIGN.
674 bup is a work in progress and there are many ways it can still be improved.
675 If you'd like to contribute patches, ideas, or bug reports, please join the
678 You can find the mailing list archives here:
680 http://groups.google.com/group/bup-list
682 and you can subscribe by sending a message to:
684 bup-list+subscribe@googlegroups.com
686 Please see <a href="HACKING">./HACKING</a> for
687 additional information, i.e. how to submit patches (hint - no pull
688 requests), how we handle branches, etc.