Cornell University

Physics Educational Computing Facility (PECF)

Backups

Each week (every Saturday early morning, to be precise) the home directories are backed up to a separate machine called backup.physics.cornell.edu on a 250 GB Seagate Barracuda hard drive. The backups maintain the permissions, so that everybody can restore his/her files without going to the System Admin. The backup partition is encrypted, which means that even if someone dismantles the backup machine and steals the hard drive, your data is non-readable. The backup is incremental, using hard links for duplicate files. Four weeks of weekly backup are kept at a time, and at the end of four weeks three of those backups are deleted to keep a single monthly backup. Twelve such monthly backups are kept over a year, and then at the end of a year eleven of those monthly backups are deleted to keep one single yearly backup.
To access a backup (i.e., to restore something), simply ssh to backup.physics.cornell.edu, and browse to the folder /backup/home (older backups) or /newbackup (newer backups). You will see backups arranged according to date and time, viz. a folder called 2006-04-22@11:15:31 is a backup finished at 11:15:31 on the 22nd of April 2006. Go into the folder corresponding to the time you want to go back to, and then into your home directory. The home directory hierarchy is usual, viz. my home directory is at Grads/2003/sbasu inside any of those folders. Simply copy whatever you want into your present home directory (denoted by ~). For example, if I wanted to restore my "courses" folder from 22nd of April, I would execute cp -a /backup/home/2006-04-22@11:15:31/Grads/2003/sbasu/courses ~/courses while I was logged in as myself.
Since the backups maintain the file permissions, you can always go into the /backup/home/WhatEverDate/your/directory and delete files you'd rather not have backed up. But please remember that such deletions are permanent; not even Linus Torvalds can bring back your data once you do this.