.. -*- restructuredtext -*- ========================================== Bacap - The extremely simple backup script ========================================== :Author: Leandro Lucarella :Contact: luca@llucax.com.ar :Copyright: Leandro Lucarella (2010), released under the BOLA_ license .. _BOLA: http://blitiri.com.ar/p/bola/ About ===== Bacap_ is a very simple script (~100 SLOC_ of Bash_) to do an incremental backup that saves space using rsync_ and hard-links. Is not the first, and it probably will not be the last, so why should you use precisely this one? I have **no** idea. All I can tell you is: 1. I did it, so it has to be great! 2. Is very simple, meaning is very easy to understand and customize. 3. You can backup multiple hosts. Did I mention is very simple? I guess that is the only selling point, so remember: **It's very simple** =) .. _Bacap: http://www.llucax.com.ar/proj/bacap/ .. _SLOC: http://en.wikipedia.org/wiki/Source_lines_of_code .. _Bash: http://www.gnu.org/software/bash/ .. _rsync: http://rsync.samba.org/ Installation ============ Doing something very complex in ~100 SLOC_ is not easy, unless you're standing in the shoulders of giants. I'm standing in the shoulders of rsync_ mainly, so you should install it before using the script. You will need a bunch of `basic POSIX commands`__, like ``date``, ``dirname``, ``readlink``, ``basename``, ``cat``, ``awk``, etc.; and ``crontab`` if you don't want to run the script manually each time you remember to actually do a backup; but I'm sure you already have those. And of course, Bash_, but again, I'm sure you have it too. If you want to backup remote hosts, be sure ssh_ is installed too. __ http://www.opengroup.org/onlinepubs/009695399/utilities/toc.html .. _ssh: http://www.openssh.com/ Once you have it all, just `download the script`__ from the git_ repo__ and copy it to wherever you like. Set the executable bit if appropriate:: chmod a+x bacap __ http://git.llucax.com.ar/w/software/bacap.git?a=blob_plain;f=bacap;hb=HEAD __ http://git.llucax.com.ar/w/software/bacap.git .. _git: http://git-scm.com/ Configuration ============= If you don't like the defaults (you probably wont), you can add a configuration file. Configuration files are searched in this places: 1. ``/etc/bacaprc`` 2. ``/etc/bacap/bacaprc`` 3. ``bacaprc`` in the same directory as the ``bacap`` script 4. Optional parameter passed as argument to the script 5. ``$CONFIG_PATH/$HOST/bacaprc`` Order is important, since all files are read (if possible) and values in the last configuration file read overwrites old values. The script takes an optional parameter, which is another location to look for a configuration file. If the configuration file passed as argument can't be found, an error will be printed (no error is issued if any of the other configuration files are missing). Also, config options could be specified on a per host basis by creating a ``bacaprc`` file in ``$CONFIG_PATH/$HOST``. As a side effect of this, configuration file(s) are read initially and each time the script backups a new host. So the configuration file(s) are read at least two times even if you backup one host. The configuration file is a Bash_ script too, and these are the default values: .. include:: bacap :literal: :start-after: #_INCLUDE_START_ :end-before: #_INCLUDE_END_ Once you've created the configuration file(s), you should create the directory ``$CONFIG_PATH`` (meaning, the value you used for that variable in the configuration file):: mkdir -p $CONFIG_PATH Then create a directory for each host you want to backup there, the directory name should be the name of the host (as you would use to connect to it using ssh_). For now let's say we will only backup ``localhost``:: mkdir $CONFIG_PATH/$LOCALHOST You should be able to guess what ``$LOCALHOST`` stands for by now =) Now, you should create at least one file there, ``paths`` which should have one line for each path to backup in that host. Let's say we want to backup only ``/etc`` and ``/home``:: echo /etc > $CONFIG_PATH/$LOCALHOST/paths echo /home >> $CONFIG_PATH/$LOCALHOST/paths But sometimes there are things there that you don't want to backup, in that case you can create a file named ``excludes`` too, and write which paths you want to exclude there, one path in each line (you can use wildcards and anything supported by the ``--exclude-from`` rsync_ option). Let's say we don't want to backup rata's home:: echo /home/rata/ > $CONFIG_PATH/$LOCALHOST/excludes Also, if you don't want to exclude files matching some pattern, you can create a file named ``includes`` with the patterns you want to include (you can use anything supported by the ``--include-from`` rsync_ option) That's pretty much it. If you want to add other hosts, just create the host directory and the needed host configuration files. Usage ===== As we said in the configuration section, the only argument the script take is an extra configuration file. All options are managed through configurations files. The script creates a new directory in ``$BACKUP_PATH/$host/$date`` and copies (hard-links) the configured paths for each ``$host``. ``$date`` is the current date at the time of starting the script, formated according to ``$DATE_FMT``. By default this has day *resolution*, but you can add hours, minutes or even seconds if you want to do more frequent backups. If the directory already exist for any host, it skips that host. A symbolic link is created at the end of the backup, with the name ``$BACKUP_PATH/$host/current``, and pointing to the newly created directory. Tips ==== Here are a few tips on how to configure Bacap_ for several common scenarios. Automating backups using cron ----------------------------- You probably want to automate your backup using *cron*. I will not include a *cron* tutorial here, but if you are completely lost, you can add this line to ``/etc/crontab`` to make a daily backup at 6:30:: 30 6 * * * root /path/to/bacap If you are a Debian_ user, you can also simply install the script in ``/etc/cron.daily`` (or make a symlink or something similar) and you are set. .. _Debian: http://www.debian.org/ Providing a ssh_ key -------------------- When doing a backup of a remote host, you probably want ssh_ to be able to login without providing a password. To do so, you can generate a ssh_ key using ``ssh-keygen``, copy the public key to the target's ``/root/.ssh/authorized_keys`` using ``ssh-copy-id root@host`` (or the user that runs the backup) and set the Bacap_ configuration variable ``RSYNC_RSH`` to something like:: RSYNC_RSH="ssh -i /path/to/priv-key -o NumberOfPasswordPrompts=0" The ``-o NumberOfPasswordPrompts=0`` is not necessary, but you would appreciate it if something is wrong with your key, since if you don't use it, rsync_ will hang asking for a password. Also, you may consider using ``StrictHostKeyChecking=no`` ssh option if you backup hosts with dynamic IP address. Backup local networks nodes (or nodes with a fast connection) ------------------------------------------------------------- When the bandwidth is not tight, you probably want to ensure ssh_ doesn't use compression:: RSYNC_RSH="ssh -o Compression=no" And if your network is trusted, you probably don't need very strong encryption either:: RSYNC_RSH="ssh -o Compression=no -c arcfour" Listing differences between 2 snapshots --------------------------------------- If you want to see what have actually changed between two backups you can run rsync_ with your usual flags plus ``-nv --delete``. For example if you just use ``-a``, to see the differences between ``lolaus/2010-07-11`` and ``lolaus/2010-07-12`` you can run:: rsync -nav --delete lolaus/2010-07-11/ lolaus/2010-07-12/ Similar alternatives ==================== * Do it yourself: this script was **heavily** inspired by an article__ by `Kevin Korb`__ (well, it was really inspired by the `previous version`__ of the article =). * `Back In Time`__: Nice looking graphical alternative. * `rsnapshot`__: A more mature and heavier alternative. I didn't really used it though, so I can't say much. __ http://www.sanitarium.net/golug/rsync_backups_2010.html __ http://www.sanitarium.net/ __ http://www.sanitarium.net/golug/rsync_backups_2005.html __ http://backintime.le-web.org/ __ http://rsnapshot.org/ I'm sure there are plenty of others, if you have one and want to be listed here, please feel free to `drop me an e-mail`__. __ mailto:luca@llucax.com.ar