https://github.com/apenwarr/bup

Please switch to using the github.com/bup/bup repo instead!
https://github.com/apenwarr/bup

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Please switch to using the github.com/bup/bup repo instead!

• Host: GitHub
• URL: https://github.com/apenwarr/bup
• Owner: apenwarr
• License: other
• Fork: true (bup/bup)
• Created: 2009-10-04T01:45:43.000Z (about 15 years ago)
• Default Branch: master
• Last Pushed: 2013-02-18T22:01:47.000Z (over 11 years ago)
• Last Synced: 2024-09-25T23:05:02.693Z (about 2 months ago)
• Language: Python
• Homepage: https://github.com/bup/bup
• Size: 2.71 MB
• Stars: 1,556
• Watchers: 62
• Forks: 23
• Open Issues: 7
• Metadata Files:
  • Readme: README
  • License: LICENSE

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README

        
bup: It backs things up

=======================

bup is a program that backs things up.  It's short for "backup." Can you

believe that nobody else has named an open source program "bup" after all

this time?  Me neither.

Despite its unassuming name, bup is pretty cool.  To give you an idea of

just how cool it is, I wrote you this poem:

                             Bup is teh awesome

                          What rhymes with awesome?

                            I guess maybe possum

                           But that's irrelevant.

			

Hmm.  Did that help?  Maybe prose is more useful after all.

Reasons bup is awesome

----------------------

bup has a few advantages over other backup software:

 - It uses a rolling checksum algorithm (similar to rsync) to split large

   files into chunks.  The most useful result of this is you can backup huge

   virtual machine (VM) disk images, databases, and XML files incrementally,

   even though they're typically all in one huge file, and not use tons of

   disk space for multiple versions.

   

 - It uses the packfile format from git (the open source version control

   system), so you can access the stored data even if you don't like bup's

   user interface.

   

 - Unlike git, it writes packfiles *directly* (instead of having a separate

   garbage collection / repacking stage) so it's fast even with gratuitously

   huge amounts of data.  bup's improved index formats also allow you to

   track far more filenames than git (millions) and keep track of far more

   objects (hundreds or thousands of gigabytes).

   

 - Data is "automagically" shared between incremental backups without having

   to know which backup is based on which other one - even if the backups

   are made from two different computers that don't even know about each

   other.  You just tell bup to back stuff up, and it saves only the minimum

   amount of data needed.

   

 - You can back up directly to a remote bup server, without needing tons of

   temporary disk space on the computer being backed up.  And if your backup

   is interrupted halfway through, the next run will pick up where you left

   off.  And it's easy to set up a bup server: just install bup on any

   machine where you have ssh access.

   

 - Bup can use "par2" redundancy to recover corrupted backups even if your

   disk has undetected bad sectors.

   

 - Even when a backup is incremental, you don't have to worry about

   restoring the full backup, then each of the incrementals in turn; an

   incremental backup *acts* as if it's a full backup, it just takes less

   disk space.

   

 - You can mount your bup repository as a FUSE filesystem and access the

   content that way, and even export it over Samba.

   

 - It's written in python (with some C parts to make it faster) so it's easy

   for you to extend and maintain.

Reasons you might want to avoid bup

-----------------------------------

 - This is a very early version. Therefore it will most probably not work

   for you, but we don't know why.  It is also missing some

   probably-critical features.

   

 - It requires python >= 2.4, a C compiler, and an installed git version >=

   1.5.3.1.

 

 - It currently only works on Linux, MacOS X >= 10.4,

   NetBSD, Solaris, or Windows (with Cygwin).  Patches to support

   other platforms are welcome.

   

   

Getting started

===============

From source

-----------

 - Check out the bup source code using git:

 

        git clone git://github.com/bup/bup

 - Install the needed python libraries (including the development

   libraries).

   On Debian/Ubuntu this is usually sufficient (run as root):

            apt-get install python2.6-dev python-fuse

            apt-get install python-pyxattr python-pylibacl

            apt-get install linux-libc-dev

   Substitute python2.5-dev or python2.4-dev if you have an older

   system.  Alternately, on newer Debian/Ubuntu versions, you can try

   this:

    

            apt-get build-dep bup

   On CentOS (for CentOS 6, at least), this should be sufficient (run

   as root):

            yum groupinstall "Development Tools"

            yum install python python-dev

            yum install fuse-python pyxattr pylibacl

            yum install perl-Time-HiRes

   In addition to the default CentOS repositories, you may need to add

   RPMForge (for fuse-python) and EPEL (for pyxattr and pylibacl).

 - Build the python module and symlinks:

        make

 	

 - Run the tests:

 

        make test

 	

    (The tests should pass.  If they don't pass for you, stop here and send

    me an email.)

 - You can install bup via "make install", and override the default

   destination with DESTDIR and PREFIX.

   Files are normally installed to "$DESTDIR/$PREFIX" where DESTDIR is

   empty by default, and PREFIX is set to /usr.  So if you wanted to

   install bup to /opt/bup, you might do something like this:

        make install DESTDIR=/opt/bup PREFIX=''

From binary packages

--------------------

Binary packages of bup are known to be built for the following OSes:

 - Debian:

    http://packages.debian.org/search?searchon=names&keywords=bup

 - Ubuntu:

    http://packages.ubuntu.com/search?searchon=names&keywords=bup

 - pkgsrc (NetBSD, Dragonfly, and others)

    http://pkgsrc.se/sysutils/bup

    http://cvsweb.netbsd.org/bsdweb.cgi/pkgsrc/sysutils/bup/

Using bup

---------

 - Try making a local backup as a tar file:

 

        tar -cvf - /etc | bup split -n local-etc -vv

 	

 - Try restoring your backup tarball:

 

        bup join local-etc | tar -tf -

 	

 - Look at how much disk space your backup took:

 

        du -s ~/.bup

 	

 - Make another backup (which should be mostly identical to the last one;

   notice that you don't have to *specify* that this backup is incremental,

   it just saves space automatically):

 

        tar -cvf - /etc | bup split -n local-etc -vv

 	

 - Look how little extra space your second backup used on top of the first:

 

 	du -s ~/.bup

 	

 - Restore your old backup again (the ~1 is git notation for "one older than

   the most recent"):

   

        bup join local-etc~1 | tar -tf -

 

 - Get a list of your previous backups:

 

        GIT_DIR=~/.bup git log local-etc

	

 - Make a backup on a remote server (which must already have the 'bup' command

   somewhere in the server's PATH (see /etc/profile, etc/environment,

   ~/.profile, or ~/.bashrc), and be accessible via ssh.

   Make sure to replace SERVERNAME with the actual hostname of your server):

   

        tar -cvf - /etc | bup split -r SERVERNAME: -n local-etc -vv

 

 - Try restoring the remote backup tarball:

 

        bup join -r SERVERNAME: local-etc | tar -tf -

 	

 - Try using the new (slightly experimental) 'bup index' and 'bup save'

   style backups, which bypass 'tar' but have some missing features (see

   "Things that are stupid" below):

   	

        bup index -uv /etc

        bup save -n local-etc /etc

   	

 - Do it again and see how fast an incremental backup can be:

 

        bup index -uv /etc

        bup save -n local-etc /etc

 	

    (You can also use the "-r SERVERNAME:" option to 'bup save', just like

     with 'bup split' and 'bup join'.  The index itself is always local,

     so you don't need -r there.)

 	

That's all there is to it!

Notes on FreeBSD

----------------

- FreeBSD's default 'make' command doesn't like bup's Makefile. In order to

  compile the code, run tests and install bup, you need to install GNU Make

  from the port named 'gmake' and use its executable instead in the commands

  seen above. (i.e. 'gmake test' runs bup's test suite)

- Python's development headers are automatically installed with the 'python'

  port so there's no need to install them separately.

- To use the 'bup fuse' command, you need to install the fuse kernel module

  from the 'fusefs-kmod' port in the 'sysutils' section and the libraries from

  the port named 'py-fusefs' in the 'devel' section.

- The 'par2' command can be found in the port named 'par2cmdline'.

- In order to compile the documentation, you need pandoc which can be found in

  the port named 'hs-pandoc' in the 'textproc' section.

Notes on NetBSD/pkgsrc

----------------------

 - See pkgsrc/sysutils/bup, which should be the most recent stable

   release and includes man pages.  It also has a reasonable set of

   dependencies (git, par2, py-fuse-bindings).

 - The "fuse-python" package referred to is hard to locate, and is a

   separate tarball for the python language binding distributed by the

   fuse project on sourceforge.  It is available as

   pkgsrc/filesystems/py-fuse-bindings and on NetBSD 5, "bup fuse"

   works with it.

 - "bup fuse" presents every directory/file as inode 0.  The directory

   traversal code ("fts") in NetBSD's libc will interpret this as a

   cycle and error out, so "ls -R" and "find" will not work.

 - It is not clear if extended attribute and POSIX acl support does

   anything useful.

How it works

============

Basic storage:

bup stores its data in a git-formatted repository.  Unfortunately, git

itself doesn't actually behave very well for bup's use case (huge numbers of

files, files with huge sizes, retaining file permissions/ownership are

important), so we mostly don't use git's *code* except for a few helper

programs.  For example, bup has its own git packfile writer written in

python.

Basically, 'bup split' reads the data on stdin (or from files specified on

the command line), breaks it into chunks using a rolling checksum (similar to

rsync), and saves those chunks into a new git packfile.  There is one git

packfile per backup.

When deciding whether to write a particular chunk into the new packfile, bup

first checks all the other packfiles that exist to see if they already have that

chunk.  If they do, the chunk is skipped.

git packs come in two parts: the pack itself (*.pack) and the index (*.idx).

The index is pretty small, and contains a list of all the objects in the

pack.  Thus, when generating a remote backup, we don't have to have a copy

of the packfiles from the remote server: the local end just downloads a copy

of the server's *index* files, and compares objects against those when

generating the new pack, which it sends directly to the server.

The "-n" option to 'bup split' and 'bup save' is the name of the backup you

want to create, but it's actually implemented as a git branch.  So you can

do cute things like checkout a particular branch using git, and receive a

bunch of chunk files corresponding to the file you split.

If you use '-b' or '-t' or '-c' instead of '-n', bup split will output a

list of blobs, a tree containing that list of blobs, or a commit containing

that tree, respectively, to stdout.  You can use this to construct your own

scripts that do something with those values.

The bup index:

'bup index' walks through your filesystem and updates a file (whose name is,

by default, ~/.bup/bupindex) to contain the name, attributes, and an

optional git SHA1 (blob id) of each file and directory.

'bup save' basically just runs the equivalent of 'bup split' a whole bunch

of times, once per file in the index, and assembles a git tree

that contains all the resulting objects.  Among other things, that makes

'git diff' much more useful (compared to splitting a tarball, which is

essentially a big binary blob).  However, since bup splits large files into

smaller chunks, the resulting tree structure doesn't *exactly* correspond to

what git itself would have stored.  Also, the tree format used by 'bup save'

will probably change in the future to support storing file ownership, more

complex file permissions, and so on.

If a file has previously been written by 'bup save', then its git blob/tree

id is stored in the index.  This lets 'bup save' avoid reading that file to

produce future incremental backups, which means it can go *very* fast unless

a lot of files have changed.

 

Things that are stupid for now but which we'll fix later

--------------------------------------------------------

Help with any of these problems, or others, is very welcome.  Join the

mailing list (see below) if you'd like to help.

 - 'bup save' and 'bup restore' have immature metadata support.

 

    On the plus side, they actually do have support now, but it's new,

    and not remotely as well tested as tar/rsync/whatever's.  If you'd

    like to help test, please do (see t/compare-trees for one

    comparison method).

    In addition, at the moment, if any strip or graft-style options

    are specified to 'bup save', then no metadata will be written for

    the root directory.  That's obviously less than ideal.

 - 'bup index' is slower than it should be.

 

    It's still rather fast: it can iterate through all the filenames on my

    600,000 file filesystem in a few seconds.  But it still needs to rewrite

    the entire index file just to add a single filename, which is pretty

    nasty; it should just leave the new files in a second "extra index" file

    or something.

   

 - bup could use inotify for *really* efficient incremental backups.

    You could even have your system doing "continuous" backups: whenever a

    file changes, we immediately send an image of it to the server.  We could

    give the continuous-backup process a really low CPU and I/O priority so

    you wouldn't even know it was running.

 - bup currently has no features that prune away *old* backups.

 

    Because of the way the packfile system works, backups become "entangled"

    in weird ways and it's not actually possible to delete one pack

    (corresponding approximately to one backup) without risking screwing up

    other backups.

   

    git itself has lots of ways of optimizing this sort of thing, but its

    methods aren't really applicable here; bup packfiles are just too huge.

    We'll have to do it in a totally different way.  There are lots of

    options.  For now: make sure you've got lots of disk space :)

 - bup has never been tested on anything but Linux, MacOS, and Windows+Cygwin.

 

    There's nothing that makes it *inherently* non-portable, though, so

    that's mostly a matter of someone putting in some effort.  (For a

    "native" Windows port, the most annoying thing is the absence of ssh in

    a default Windows installation.)

    

 - bup needs better documentation.

 

    According to a recent article about git in Linux Weekly News

    (https://lwn.net/Articles/380983/), "it's a bit short on examples and

    a user guide would be nice."  Documentation is the sort of thing that

    will never be great unless someone from outside contributes it (since

    the developers can never remember which parts are hard to understand).

    

 - bup is "relatively speedy" and has "pretty good" compression.

 

    ...according to the same LWN article.  Clearly neither of those is good

    enough.  We should have awe-inspiring speed and crazy-good compression. 

    Must work on that.  Writing more parts in C might help with the speed.

   

 - bup has no GUI.

 

    Actually, that's not stupid, but you might consider it a limitation. 

    There are a bunch of Linux GUI backup programs; someday I expect someone

    will adapt one of them to use bup.

    

    

More Documentation

------------------

bup has an extensive set of man pages.  Try using 'bup help' to get

started, or use 'bup help SUBCOMMAND' for any bup subcommand (like split,

join, index, save, etc.) to get details on that command.

For further technical details, please see ./DESIGN.

How you can help

================

bup is a work in progress and there are many ways it can still be improved.

If you'd like to contribute patches, ideas, or bug reports, please join the

bup mailing list.

You can find the mailing list archives here:

	http://groups.google.com/group/bup-list

	

and you can subscribe by sending a message to:

	[email protected]

Please see ./HACKING for

additional information, i.e. how to submit patches (hint - no pull

requests), how we handle branches, etc.

Have fun,

Avery