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 - This is a very early version. Therefore it will most probably not work
71 for you, but we don't know why. It is also missing some
72 probably-critical features.
74 - It requires python >= 2.6, a C compiler, and an installed git
75 version >= 1.5.3.1. 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/0.29.1-from-0.29.md">Changes in 0.29.1 as compared to 0.29</a>
90 - <a href="note/0.29-from-0.28.1.md">Changes in 0.29 as compared to 0.28.1</a>
91 - <a href="note/0.28.1-from-0.28.md">Changes in 0.28.1 as compared to 0.28</a>
92 - <a href="note/0.28-from-0.27.1.md">Changes in 0.28 as compared to 0.27.1</a>
93 - <a href="note/0.27.1-from-0.27.md">Changes in 0.27.1 as compared to 0.27</a>
102 - Check out the bup source code using git:
104 git clone https://github.com/bup/bup
106 - This will leave you on the master branch, which is perfect if you
107 would like to help with development, but if you'd just like to use
108 bup, please check out the latest stable release like this:
112 You can see the latest stable release here:
113 https://github.com/bup/bup/releases.
115 - Install the required python libraries (including the development
118 On very recent Debian/Ubuntu versions, this may be sufficient (run
121 apt-get build-dep bup
123 Otherwise try this (substitute python2.6-dev if you have an older
126 apt-get install python2.7-dev python-fuse
127 apt-get install python-pyxattr python-pylibacl
128 apt-get install linux-libc-dev
129 apt-get install acl attr
130 apt-get install python-tornado # optional
132 On CentOS (for CentOS 6, at least), this should be sufficient (run
135 yum groupinstall "Development Tools"
136 yum install python python-devel
137 yum install fuse-python pyxattr pylibacl
138 yum install perl-Time-HiRes
140 In addition to the default CentOS repositories, you may need to add
141 RPMForge (for fuse-python) and EPEL (for pyxattr and pylibacl).
143 On Cygwin, install python, make, rsync, and gcc4.
145 If you would like to use the optional bup web server on systems
146 without a tornado package, you may want to try this:
150 - Build the python module and symlinks:
158 The tests should pass. If they don't pass for you, stop here and
159 send an email to bup-list@googlegroups.com. Though if there are
160 symbolic links along the current working directory path, the tests
161 may fail. Running something like this before "make test" should
162 sidestep the problem:
166 - You can install bup via "make install", and override the default
167 destination with DESTDIR and PREFIX.
169 Files are normally installed to "$DESTDIR/$PREFIX" where DESTDIR is
170 empty by default, and PREFIX is set to /usr/local. So if you wanted to
171 install bup to /opt/bup, you might do something like this:
173 make install DESTDIR=/opt/bup PREFIX=''
175 - The Python executable that bup will use is chosen by ./configure,
176 which will search for a reasonable version unless PYTHON is set in
177 the environment, in which case, bup will use that path. You can
178 see which Python executable was chosen by looking at the
179 configure output, or examining cmd/python-cmd.sh, and you can
180 change the selection by re-running ./configure.
185 Binary packages of bup are known to be built for the following OSes:
188 http://packages.debian.org/search?searchon=names&keywords=bup
190 http://packages.ubuntu.com/search?searchon=names&keywords=bup
191 - pkgsrc (NetBSD, Dragonfly, and others)
192 http://pkgsrc.se/sysutils/bup
193 http://cvsweb.netbsd.org/bsdweb.cgi/pkgsrc/sysutils/bup/
195 https://www.archlinux.org/packages/?sort=&q=bup
197 https://apps.fedoraproject.org/packages/bup
203 - Get help for any bup command:
212 - Initialize the default BUP_DIR (~/.bup):
216 - Make a local backup (-v or -vv will increase the verbosity):
219 bup save -n local-etc /etc
221 - Restore a local backup to ./dest:
223 bup restore -C ./dest local-etc/latest/etc
226 - Look at how much disk space your backup took:
230 - Make another backup (which should be mostly identical to the last one;
231 notice that you don't have to *specify* that this backup is incremental,
232 it just saves space automatically):
235 bup save -n local-etc /etc
237 - Look how little extra space your second backup used (on top of the first):
241 - Get a list of your previous backups:
245 - Restore your first backup again:
247 bup restore -C ./dest-2 local-etc/2013-11-23-11195/etc
249 - Make a backup to a remote server which must already have the 'bup' command
250 somewhere in its PATH (see /etc/profile, etc/environment, ~/.profile, or
251 ~/.bashrc), and be accessible via ssh.
252 Make sure to replace SERVERNAME with the actual hostname of your server:
254 bup init -r SERVERNAME:path/to/remote-bup-dir
256 bup save -r SERVERNAME:path/to/remote-bup-dir -n local-etc /etc
258 - Make a remote backup to ~/.bup on SERVER:
261 bup save -r SERVER: -n local-etc /etc
263 - See what saves are available in ~/.bup on SERVER:
267 - Restore the remote backup to ./dest:
269 bup restore -r SERVER: -C ./dest local-etc/latest/etc
272 - Defend your backups from death rays (OK fine, more likely from the
273 occasional bad disk block). This writes parity information
274 (currently via par2) for all of the existing data so that bup may
275 be able to recover from some amount of repository corruption:
279 - Use split/join instead of index/save/restore. Try making a local
282 tar -cvf - /etc | bup split -n local-etc -vv
284 - Try restoring the tarball:
286 bup join local-etc | tar -tf -
288 - Look at how much disk space your backup took:
292 - Make another tar backup:
294 tar -cvf - /etc | bup split -n local-etc -vv
296 - Look at how little extra space your second backup used on top of
301 - Restore the first tar backup again (the ~1 is git notation for "one
302 older than the most recent"):
304 bup join local-etc~1 | tar -tf -
306 - Get a list of your previous split-based backups:
308 GIT_DIR=~/.bup git log local-etc
310 - Save a tar archive to a remote server (without tar -z to facilitate
313 tar -cvf - /etc | bup split -r SERVERNAME: -n local-etc -vv
315 - Restore the archive:
317 bup join -r SERVERNAME: local-etc | tar -tf -
319 That's all there is to it!
325 - FreeBSD's default 'make' command doesn't like bup's Makefile. In order to
326 compile the code, run tests and install bup, you need to install GNU Make
327 from the port named 'gmake' and use its executable instead in the commands
328 seen above. (i.e. 'gmake test' runs bup's test suite)
330 - Python's development headers are automatically installed with the 'python'
331 port so there's no need to install them separately.
333 - To use the 'bup fuse' command, you need to install the fuse kernel module
334 from the 'fusefs-kmod' port in the 'sysutils' section and the libraries from
335 the port named 'py-fusefs' in the 'devel' section.
337 - The 'par2' command can be found in the port named 'par2cmdline'.
339 - In order to compile the documentation, you need pandoc which can be found in
340 the port named 'hs-pandoc' in the 'textproc' section.
343 Notes on NetBSD/pkgsrc
344 ----------------------
346 - See pkgsrc/sysutils/bup, which should be the most recent stable
347 release and includes man pages. It also has a reasonable set of
348 dependencies (git, par2, py-fuse-bindings).
350 - The "fuse-python" package referred to is hard to locate, and is a
351 separate tarball for the python language binding distributed by the
352 fuse project on sourceforge. It is available as
353 pkgsrc/filesystems/py-fuse-bindings and on NetBSD 5, "bup fuse"
356 - "bup fuse" presents every directory/file as inode 0. The directory
357 traversal code ("fts") in NetBSD's libc will interpret this as a
358 cycle and error out, so "ls -R" and "find" will not work.
360 - There is no support for ACLs. If/when some entrprising person
361 fixes this, adjust t/compare-trees.
367 - There is no support for ACLs. If/when some enterprising person
368 fixes this, adjust t/compare-trees.
370 - In t/test.sh, two tests have been disabled. These tests check to
371 see that repeated saves produce identical trees and that an
372 intervening index doesn't change the SHA1. Apparently Cygwin has
373 some unusual behaviors with respect to access times (that probably
374 warrant further investigation). Possibly related:
375 http://cygwin.com/ml/cygwin/2007-06/msg00436.html
381 - There is no support for ACLs. If/when some enterprising person
382 fixes this, adjust t/compare-trees.
391 bup stores its data in a git-formatted repository. Unfortunately, git
392 itself doesn't actually behave very well for bup's use case (huge numbers of
393 files, files with huge sizes, retaining file permissions/ownership are
394 important), so we mostly don't use git's *code* except for a few helper
395 programs. For example, bup has its own git packfile writer written in
398 Basically, 'bup split' reads the data on stdin (or from files specified on
399 the command line), breaks it into chunks using a rolling checksum (similar to
400 rsync), and saves those chunks into a new git packfile. There is at least one
401 git packfile per backup.
403 When deciding whether to write a particular chunk into the new packfile, bup
404 first checks all the other packfiles that exist to see if they already have that
405 chunk. If they do, the chunk is skipped.
407 git packs come in two parts: the pack itself (*.pack) and the index (*.idx).
408 The index is pretty small, and contains a list of all the objects in the
409 pack. Thus, when generating a remote backup, we don't have to have a copy
410 of the packfiles from the remote server: the local end just downloads a copy
411 of the server's *index* files, and compares objects against those when
412 generating the new pack, which it sends directly to the server.
414 The "-n" option to 'bup split' and 'bup save' is the name of the backup you
415 want to create, but it's actually implemented as a git branch. So you can
416 do cute things like checkout a particular branch using git, and receive a
417 bunch of chunk files corresponding to the file you split.
419 If you use '-b' or '-t' or '-c' instead of '-n', bup split will output a
420 list of blobs, a tree containing that list of blobs, or a commit containing
421 that tree, respectively, to stdout. You can use this to construct your own
422 scripts that do something with those values.
427 'bup index' walks through your filesystem and updates a file (whose name is,
428 by default, ~/.bup/bupindex) to contain the name, attributes, and an
429 optional git SHA1 (blob id) of each file and directory.
431 'bup save' basically just runs the equivalent of 'bup split' a whole bunch
432 of times, once per file in the index, and assembles a git tree
433 that contains all the resulting objects. Among other things, that makes
434 'git diff' much more useful (compared to splitting a tarball, which is
435 essentially a big binary blob). However, since bup splits large files into
436 smaller chunks, the resulting tree structure doesn't *exactly* correspond to
437 what git itself would have stored. Also, the tree format used by 'bup save'
438 will probably change in the future to support storing file ownership, more
439 complex file permissions, and so on.
441 If a file has previously been written by 'bup save', then its git blob/tree
442 id is stored in the index. This lets 'bup save' avoid reading that file to
443 produce future incremental backups, which means it can go *very* fast unless
444 a lot of files have changed.
447 Things that are stupid for now but which we'll fix later
448 ========================================================
450 Help with any of these problems, or others, is very welcome. Join the
451 mailing list (see below) if you'd like to help.
453 - 'bup save' and 'bup restore' have immature metadata support.
455 On the plus side, they actually do have support now, but it's new,
456 and not remotely as well tested as tar/rsync/whatever's. However,
457 you have to start somewhere, and as of 0.25, we think it's ready
458 for more general use. Please let us know if you have any trouble.
460 Also, if any strip or graft-style options are specified to 'bup
461 save', then no metadata will be written for the root directory.
462 That's obviously less than ideal.
464 - bup is overly optimistic about mmap. Right now bup just assumes
465 that it can mmap as large a block as it likes, and that mmap will
466 never fail. Yeah, right... If nothing else, this has failed on
467 32-bit architectures (and 31-bit is even worse -- looking at you,
470 To fix this, we might just implement a FakeMmap[1] class that uses
471 normal file IO and handles all of the mmap methods[2] that bup
472 actually calls. Then we'd swap in one of those whenever mmap
475 This would also require implementing some of the methods needed to
476 support "[]" array access, probably at a minimum __getitem__,
477 __setitem__, and __setslice__ [3].
479 [1] http://comments.gmane.org/gmane.comp.sysutils.backup.bup/613
480 [2] http://docs.python.org/2/library/mmap.html
481 [3] http://docs.python.org/2/reference/datamodel.html#emulating-container-types
483 - 'bup index' is slower than it should be.
485 It's still rather fast: it can iterate through all the filenames on my
486 600,000 file filesystem in a few seconds. But it still needs to rewrite
487 the entire index file just to add a single filename, which is pretty
488 nasty; it should just leave the new files in a second "extra index" file
491 - bup could use inotify for *really* efficient incremental backups.
493 You could even have your system doing "continuous" backups: whenever a
494 file changes, we immediately send an image of it to the server. We could
495 give the continuous-backup process a really low CPU and I/O priority so
496 you wouldn't even know it was running.
498 - bup only has experimental support for pruning old backups.
500 While you should now be able to drop old saves and branches with
501 `bup rm`, and reclaim the space occupied by data that's no longer
502 needed by other backups with `bup gc`, these commands are
503 experimental, and should be handled with great care. See the
504 man pages for more information.
506 Unless you want to help test the new commands, one possible
507 workaround is to just start a new BUP_DIR occasionally,
508 i.e. bup-2013, bup-2014...
510 - bup has never been tested on anything but Linux, FreeBSD, NetBSD,
511 OS X, and Windows+Cygwin.
513 There's nothing that makes it *inherently* non-portable, though, so
514 that's mostly a matter of someone putting in some effort. (For a
515 "native" Windows port, the most annoying thing is the absence of ssh in
516 a default Windows installation.)
518 - bup needs better documentation.
520 According to a recent article about bup in Linux Weekly News
521 (https://lwn.net/Articles/380983/), "it's a bit short on examples and
522 a user guide would be nice." Documentation is the sort of thing that
523 will never be great unless someone from outside contributes it (since
524 the developers can never remember which parts are hard to understand).
526 - bup is "relatively speedy" and has "pretty good" compression.
528 ...according to the same LWN article. Clearly neither of those is good
529 enough. We should have awe-inspiring speed and crazy-good compression.
530 Must work on that. Writing more parts in C might help with the speed.
534 Actually, that's not stupid, but you might consider it a
535 limitation. See the ["Related Projects"](https://bup.github.io/)
536 list for some possible options.
541 bup has an extensive set of man pages. Try using 'bup help' to get
542 started, or use 'bup help SUBCOMMAND' for any bup subcommand (like split,
543 join, index, save, etc.) to get details on that command.
545 For further technical details, please see ./DESIGN.
551 bup is a work in progress and there are many ways it can still be improved.
552 If you'd like to contribute patches, ideas, or bug reports, please join the
555 You can find the mailing list archives here:
557 http://groups.google.com/group/bup-list
559 and you can subscribe by sending a message to:
561 bup-list+subscribe@googlegroups.com
563 Please see <a href="HACKING">./HACKING</a> for
564 additional information, i.e. how to submit patches (hint - no pull
565 requests), how we handle branches, etc.