Backup/Restore

If a file is lost from your account (e.g., if you accidentally removed a file you need), the file can usually be restored, since disk backups and filesystem snapshots are done on a regular basis for most user-accessible filesystems. If you lose a file from your home directory or project space, it can usually be recovered by looking in the snapshot tree. If, however, your file was lost from a filesystem on which snapshots have been disabled, or if it is not in the snapshot tree for some reason, fill out the "Restore Files" form in the box to the left. Please specify the name of the file, including the path name of the subdirectory it was in, the date the file was most recently modified, and the date it was lost.

If you need help understanding this policy, please e-mail csstaff@cs.princeton.edu for clarification.

Backup Schedule (effective: 2015/07/01)

The following backup schedule is currently in effect for the CS Department. Backup dates and times are unspecified and are effectively random.

  • For all Home Directories:
    • User-accessible snapshots.
    • Bi-weekly offsite DR backups with a retention period of 30 days.
  • For Project Filesystems:
    • User-accessible snapshots.
    • Bi-weekly offsite DR backups with a retention period of 30 days.

Backups more than one year old are not available.

Snapshots

Home Directories and Project Space are both stored on filesystems that support snapshots. Snapshots are taken every four hours, and deleted on a regular basis such that there are generally several snapshots available from various times going back as far as one year.

In order to recover a lost file from the snapshot tree, cd into the directory from which you lost the file, and then into the '.snapshot' directory within that directory. You will not see the .snapshot directory in the output of 'ls', but if you are using a central CS filesystem (and have not made special arrangements to prevent it), it will be there. Below is an example of recovering a file called 'file' from the 'code' directory in the 'myproject' filesystem:


    tux$ cd /n/fs/myproject/code
    tux$ cd .snapshot
    tux$ pwd
    /n/fs/myproject/code/.snapshot
    tux$ ls
    20111201-00:30-MONTHLY-PROJ/    20120216-00:00-NIGHTLY-PROJ/
    20120101-00:30-MONTHLY-PROJ/    20120216-12:00-Q4H-PROJ/
    20120130-00:00-WEEKLY-PROJ/     20120216-16:00-Q4H-PROJ/
    20120201-00:30-MONTHLY-PROJ/    20120216-20:00-Q4H-PROJ/
    20120201-01:00-QUARTERLY-PROJ/  20120217-00:00-NIGHTLY-PROJ/
    20120206-00:00-WEEKLY-PROJ/     20120217-04:00-Q4H-PROJ/
    20120213-00:00-WEEKLY-PROJ/     20120217-08:00-Q4H-PROJ/
    20120215-00:00-NIGHTLY-PROJ/
    tux$ cd 20120217-04:00-Q4H-PROJ
    tux$ pwd
    /n/fs/myproject/code/.snapshot/20120217-04:00-Q4H-PROJ
    tux$ cp -p file /n/fs/myproject/code