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I've modified a script to backup live xen images with dar. This script uses lvm to snapshot a running VM disk, then mount it read only and uses dar to create an incremental backup. The script is a derivative of a script I've found on the net [1]. There is still a small problem with journaled file system that even if the fs is frozen before taking the snapshot, for some reason, even if I mount it read only, the kernel module tries to go through the journal to recover the fs. I'm worried that this might lead to data corruptions... There is this old thread [2] shading a bit of light on the problem.

The script is pretty simple. To create a full backup of a xen domain the command line is:

./xenBackup.sh -d domainname


to create an incremental backup :

./xenBackup.sh -d domainname -i 1

where -i is the sequence number of the incremental backup. Of course you need the previous incremental backup for the operation to be successful (if i = 1, you need a full backup) . You can use this script from cron, running a full backup on sunday and an incremental backup every day of the week.

Script attached.

[1] http://www.johnandcailin.com/blog/john/backing-your-xen-domains
[2] http://www.nabble.com/Xen-backups-using-LVM-Snapshots-td19988096.html