I accidentally deleted a bunch of important files from a jail that was running FreeNAS 9.3; but will work on FreeBSD as well. Luckily, I had setup my jails to have periodic snapshots taken for just this very reason.

ZFS to the rescue!¶

• Log into the FreeNAS administration panel and open a Shell.

• Check the status of the snapdir for the examplejail jail zvol:
  

  zfs get snapdir zpool/jails/examplejail
  

  • Example output:
    

    NAME                     PROPERTY  VALUE    SOURCE
    zpool/jails/examplejail  snapdir   hidden   default
    

• Set the snapdir value to visible:
  

  zfs set snapdir=visible zpool/jails/examplejail
  

• Check which snapshots are available:
  

  ls /mnt/zpool/jails/examplejail/.zfs/snapshot/
  

  • Example output:
    

    auto-20160330.0900-2w   auto-20160405.0900-2w   auto-20160411.0900-2w           
    auto-20160331.0900-2w   auto-20160406.0900-2w   auto-20160412.0900-2w           
    auto-20160401.0900-2w   auto-20160407.0900-2w                                   
    auto-20160404.0900-2w   auto-20160408.0900-2w
    

• Now use rsync to copy the files back to the original jail:
  

  rsync -avh -n /mnt/zpool/jails/examplejail/.zfs/snapshot/auto-20160411.0900-2w/var/vmail/vmail1/example.com/bob/ /mnt/zpool/jails/examplejail/var/vmail/vmail1/example.com/bob/
  

  • NOTE: Make sure to remove the -n (dryrun) flag to run the sync for real, or else you won't actually be copying the data.

• When the sync is complete set the example jail zvol snapdir property back to hidden:
  

  zfs set snapdir=hidden zpool/jails/examplejail
  

Resources¶

• https://www.freebsd.org/doc/handbook/zfs-zfs.html
• https://wiki.freebsd.org/ZFSQuickStartGuide