Filesystem Backups in the CS Department

Retention Policy for Junkfood Home Directories and Web Directories

An hourly copy is kept for 5 days.
A daily copy is kept for 2 weeks.
A weekly copy is kept for 2 months.
A monthly copy is kept for 2 years.

Recovering Files

If you need to restore a file from your Junkfood Home Directory or your Web Directory (www.cs.umd.edu/~user), follow the simple steps below.

To restore a file from “junkfood home”:

1. Log in to a junkfood system.

2. Go to the backup directory: cd /fs/userdata/.zfs/snapshot

3. Snapshot directories are named zrepl_YYYYMMDD_HHMMSS_000 (date and time in UTC). Snapshots are not kept at hourly resolution forever — once one ages past 5 days it is thinned down to the daily/weekly/monthly copies described above, so an exact hour you remember may no longer exist. To see every snapshot that exists for a given day, e.g. August 14, 2026, list them with a wildcard:

   ls -d zrepl_20260814_*

   or match just the date with a regular expression:

   find . -maxdepth 1 -regextype posix-extended -regex './zrepl_20260814_[0-9]\{6\}_000'

   Then cd into the one you want, appending your username and then junkfood (your actual home directory data lives one level deeper, in a junkfood subdirectory of this export), e.g.:

   cd zrepl_20260814_060000_000/jworden/junkfood

4. Copy the desired file back to the desired junkfood home directory:

   cp deletedFile ~/folderName

To restore a file from www.cs.umd.edu/~userName:

1. Log in to a junkfood system.

2. cd /fs/wwwusers/.zfs/snapshot

3. Snapshot directories are named zrepl_YYYYMMDD_HHMMSS_000 (date and time in UTC). Snapshots are not kept at hourly resolution forever — once one ages past 5 days it is thinned down to the daily/weekly/monthly copies described above, so an exact hour you remember may no longer exist. To see every snapshot that exists for a given day, e.g. August 14, 2026, list them with a wildcard:

   ls -d zrepl_20260814_*

   or match just the date with a regular expression:

   find . -maxdepth 1 -regextype posix-extended -regex './zrepl_20260814_[0-9]\{6\}_000'

   Then cd into the one you want, appending your username, e.g.:

   cd zrepl_20260814_060000_000/jworden

4. Copy the desired file back to your web directory:

   cp deletedFile /fs/wwwusers/$USER/folderName

Please note that /tmp directories on the junkfood machines are not backed up. Any data that was written there will not be retrievable when the /tmp is cleared by a system reboot.

If you are unable to find the desired file or you would like to restore a file from a system not mentioned here, please email IT staff by staff at cs.umd.edu. Include the information that you last accessed successfully and recover to where.

To restore a file from www.cs.umd.edu/class/cmscXXX:

1. Log in to a junkfood system.

2. cd /fs/www/.zfs/snapshot

3. Snapshot directories are named zrepl_YYYYMMDD_HHMMSS_000 (date and time in UTC). Snapshots are not kept at hourly resolution forever — once one ages past 5 days it is thinned down to the daily/weekly/monthly copies described above, so an exact hour you remember may no longer exist. To see every snapshot that exists for a given day, e.g. August 14, 2026, list them with a wildcard:

   ls -d zrepl_20260814_*

   or match just the date with a regular expression:

   find . -maxdepth 1 -regextype posix-extended -regex './zrepl_20260814_[0-9]\{6\}_000'

   Then cd into the one you want, e.g.: cd zrepl_20260814_060000_000/class/cmscXXX

4. Copy the desired file back to a directory:

   cp deletedFile /tmp

Please note that /tmp directories on the junkfood machines are not backed up. Any data that was written there will not be retrievable when the /tmp is cleared by a system reboot.

If you are unable to find the desired file or you would like to restore a file from a system not mentioned here, please contact IT staff by completing this form.

To restore a file from a project site (/fs/www/projects, e.g. projects.cs.umd.edu):

1. Log in to a junkfood system, or any workstation where /fs/www/projects is available.

2. Go to the snapshot directory: cd /fs/www/projects/.snap

3. Snapshot directories here are named differently than the ones above — by date and time in UTC, but formatted like scheduled-2026-07-17-16_00_00_UTC. Go to, for example: cd scheduled-2026-07-17-16_00_00_UTC/yourProjectDirectory/

4. Copy the desired file back to your project directory:

   cp deletedFile /fs/www/projects/yourProjectDirectory/

Snapshots here follow the same retention as the policy above (hourly for 5 days, daily for 2 weeks, weekly for 2 months, monthly for 2 years).

If you are unable to find the desired file, please email IT staff by staff at cs.umd.edu.