Time Machine for Linux

Since Apple’s recent release of Leopard, which comes with the wonderful backup solution Time Machine, I’ve seen more than a few articles explaining how those with Linux/Unix machines can create there own incremental backups using rsync. This is great and, short of hard-linked directories, exactly like Apple’s Time Machine backend. Furthermore, this has always been possible on systems with rsync available and filesystems that support hardlinks. I’ve been doing incremental backups for years but, unlike all of the recent articles in question, I didn’t roll my own solution: I use ‘rsnapshot’ to do all of the hard work for me.

There are a number of tutorials for setting up rsnapshot and the process is really quite simple. First, install rsnapshot; if you’re using a system with a good package manager, then this is a trivial operation:

~$ sudo aptitude install rsnapshot

Next, you must edit the rsnapshot.conf file which, in most Linux distributions, resides in /etc. Note that the key/value pairs in this file must be tab delimited. The file is well commented; the major things that need to be changed are:

• snapshot_root - where the backups will be stored
• backup intervals - how many of each interval to keep around (I do 7 dailys, 4 weeklys and 3 monthlys)
• backup points - what to backup

The last point requires some elaboration, as this is what rsnapshot will be backing up. for a server that is only backing up it’s own stuff this can be fairly simple:

backup    /etc/            servername/
backup    /var/lib/svn/    servername/
backup    /home/           servername/

Which tells rsnapshot to backup /etc, /home and the subversion repository and place them in the directory servername under the snapshot_root directory. rsnapshot is also capable of backup up remote hosts via ssh:

backup    root@remote:/etc/     remote/     +rsync_long_args=--bwlimit=120
backup    root@remote:/home/    remote/     +rsync_long_args=--bwlimit=120

As above, this will backup the contents of the specified directories under the remote_host directory in your snapshot_root directory. This also gives an example of passing arguments to rsync for that host. I use this to backup my home machine to my server; since I’m on a residential internet link, I tell rsync to limit its bandwidth usage to 120 kilobytes per second when it is backing up this host to keep from saturating the pipe.