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Recovering Files from AFS Backups

  Tim Whibley, Rainer Tobbicke IT/DCI

Attention! This article is OLD and probably OBSOLETE.

This article describes the scheme for backing up and restoring AFS files. It includes several examples on recovering files which have been lost and explains the procedures we have adopted as well as some of the internal details for those interested.

AFS Backups Procedure

Currently backups are provided by the native AFS backup system. Data in AFS is backed up on a volume basis and typically each user's home directory is a single volume.

To find the name of the AFS volume housing your AFS home directory, from your AFS account try the command `fs lsmount $HOME', e.g.:

  fs lsmount $HOME

  '/afs/cern.ch/user/t/tim' is a mount point for volume '#user.tim'

Every night, an AFS backup clone is created for each user volume. To find out when this clone is created, try the command `vos exam user.username.backup', e.g.:

  vos exam user.tim.backup

  user.tim.backup               536899468 BK    8509 K  On-line
    afs2.cern.ch /vicepad 
    RWrite  536899466 ROnly          0 Backup  536899468 
    MaxQuota      50000 K 
    Creation    Tue Feb 18 22:32:45 1997
    Last Update Tue Feb 18 22:32:45 1997
    551 accesses in the past day (i.e., vnode references)

    RWrite: 536899466     Backup: 536899468 
    number of sites -> 1
      server afs2.cern.ch partition /vicepad RW Site

This is a snapshot of an AFS volume and it is recreated every night.
This snapshot is mounted on /afs/cern.ch/ubackup/initial/username
e.g. /afs/cern.ch/ubackup/t/tim

Getting Back AFS Files

The two following pairs of "Question & Answer" explain what you can do when you lose some AFS files:

Question   I have just deleted an AFS file today. How can I get this file back ?

Answer

• For user volumes

  Look in /afs/cern.ch/ubackup/initial/userid
  e.g.: ls /afs/cern.ch/ubackup/t/tim

  Since the files in /ubackup are on disk, you can use the command `cp' to copy these files. However, the files in ubackup are recreated every night, so see the next question for recovering files not found in ubackup. The same access rights for AFS home directories apply to directories in /afs/cern.ch/ubackup.
  N.B.The CERN AFS User's Guide version 1.2 explains file permissions in detail.
  

• For project volumes

  1) Using the directory or file name which has been lost, issue the `fs examine' command
  (fs examine <dir/file path>) and note the volume name:

  
    fs exam /afs/cern.ch/project/parc/p3_all/alpha_osf32
  
    Volume status for vid = 536916469 named p.parc.patran
    Current disk quota is 900000 
    Current blocks used are 789078 
    The partition has 4219332 blocks available out of 12533760 
  
  

  2) `cd' to your home directory and mount the backup volume using a temporary non-existing name:

    cd
    fs mkmount temp <volume-name>.backup
  

  E.g.: `fs mkmount temp p.parc.patran.backup'

  3) look for your files below the temp subdirectory and copy them somewhere safe.

  4) remove the unnecessary mount point:

    cd
    fs rmmount temp
  

Question   I lost some AFS files some days (weeks/months) ago. How can I get them back ?

Answer If the file is less than one year old, mail Afs.Support@cern.ch.

N.B. We need to know:

1. the full pathname of the filename(s) that you need restoring;
   e.g. /afs/cern.ch/user/t/tim/file1
2. the date from which you need these files restoring.

See next section (AFS Tape Restores) for more details.

AFS Tape Restores

Unfortunately, tape restores cannot be be performed by users so you will have to send a mail to Afs.Support@cern.ch with the following information:

1. the full pathname of the filename(s) that you need restoring,
   e.g. /afs/cern.ch/user/t/tim/file1
2. the date from which you need these files restoring.

  p.project.R - for project volumes
  user.username.R - for user volumes

A mail will then be sent to you explaining the procedure to mount this volume and copy your files to a safe place. You should then reply to this mail when you have recovered your files in order that we can remove this .R volume.

AFS Backup Details

Please note the following concerning the AFS tape backups:

• they run nightly,
• full backups (level 0) are performed fortnightly,
• they use DLT tape stackers,
• tape restores cannot be be performed by users - mail afs.support@cern.ch,
• you can restore on a daily basis for files up to a month old,
• you can restore on a monthly basis for files over one month old,
• tapes are recycled after one year,
• some tapes are kept in a separate building so restores can take up to 24 hours.