Data backed up include the following information:

• User home directories stored on the Unix servers 
• Lessons home directories stored on the Unix servers 
• System state data 
• User mailboxes on the central filesystem on the mailhost. 

User directories on Windows machines, the content of the filesystems /spare on Debian machines and generally any data not explicitly mentioned above are not backed up, and responsibility for backups in this case belongs to users. 

Backups are run once weekly. Backups of home directories are kept for six months, copies of mailboxes for three. Servers data backup are kept for six months.

Each backup saves the contents of files/directories on the servers at the time the backup is performed. This means that the backups don't record all activities: it is possible for a user to create/modify/delete a file between two backups, which will never appear on a backup. This is also true of emails: a user may receive, read and delete an email message without the backup of the mailboxes recording that message (although there would normally be a record of sender and receiver of an email - without the contents - in the mailhost logs). 

Users in need of data restore should send an email to sysadm AT csd.uoc.gr including information such as file(s)/directories names, last change date/time and date/time of deletion.