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23. Backup

Windows NT Backup only backs up files to other volumes or tape drives supported by the HCL. It does not back up to floppies. Users can backup files for which they have Read permission. The Backup Files and Directories user right is required for backing up and the Restore Files and Directories user right is required for restoring data. The groups Backup Operators and the Server Operators have these rights.

A network backup means one person can do the work, but users must put their important files on the server, the network traffic is more intensive though and the registry can not be backed up over the network. A local backup uses less network resources but the users are responsible for carrying out their own backup to tape.

If a file is in use, NT backs up the last saved version.

The registry on a domain controller contains all the user accounts and must be backed up. It can only be backed up to a tape within the same computer so make sure that the tape drive is in the domain controller.

Files have an archive attribute which is a backup marker. If it is set then the marker indicates that the file has been backed up.

There are the following backup types:

  • Normal - selected files, marking their archive attributes
  • Copy - selected files without marking their archive attributes. This is good for making tape copies that do not interfere with archive backups, since it does not set the archive attribute.
  • Incremental - selected files, marking their archive attributes, but only backs up the ones that have changed since the last backup.
  • Differential - selected files, NOT marking their archive attributes, but only backs up the ones that have changed since the last backup.
  • Daily - only backs up files that have changed that day, does not mark their archive attributes.

A Backup Set is one backup operation for files and folders from a single volume. A Catalog is a picture of the backup and this is placed on the backup tape. The tape catalog shows the backup sets on a tape whilst the backup set catalog shows the files and folders. A Backup Log is a text file that records the backup operations. This log can contain the date, the user, the type of backup, the files, the computer, the tape drive location and the tape-set number.

The Backup program is run from the Administrative Tools menu (erasing a tape is achieved by selecting Erase Tape). In the drives window, check the files and folders that you need to back up. When you click Backup you can input a tape name and select the following options:

  • Append - add a new backup set to existing backup sets.
  • Replace
  • Verify After Backup
  • Backup Registry
  • Restrict Access to Owner or Administrator
  • Hardware Compression - the tape drive needs to support this
  • Pick the backup type.
  • Log Information - decide a name of the log file to be stored in \systemroot, plus whether the log should contain full detail or just a summary. It is a good idea to keep a printed copy of the log for future reference.

An example of a batch file for a scheduled backup follows:

cmd /c net use x: \\mary\public
cmd /c net use y: \\john\public
ntbackup backup c: d: x: y: \\mainserver\public /T Incremental /b /hc:on /v /l "c:\weekly.log"
cmd /c net use x: /delete
cmd /c net use y: /delete

The first two lines connect the server on to computers called mary and john and the volumes x: and y: are mapped to the public folders on these computers. The next line uses the ntbackup backup source paths destination path command and it has the following syntax:

  • /a - appends
  • /b - backs up the local registry
  • /d "text" - description
  • /e - summary log instead of default full detail log.
  • /l "filename" - the log filename
  • /r - limits access to the administrators, owner or backup operators.
  • /t Normal | Copy | Incremental | Differential | Daily
  • /v - verify
  • /hc:on | off - hardware compression

Take the following steps to perform a scheduled backup:

  • In Administrative Tools click on Server Manager
  • Under Computer, select the computer name and click Services on the Computer menu.
  • Under Service, select Schedule and click Startup.
  • Under Startup Type select Automatic
  • Under Service, select Schedule and click Start
  • Use the at command with the following syntax at \\computer_name id /delete time interactive /every:date next: date "command" , where command would be ntbackup. Delete means that the scheduled command is cancelled. Interactive means that the job will be visible on the desktop of the user.

Restoring data needs the following steps:

  • When restoring a backup the tape catalog must be loaded first. This is achieved by starting the Backup program and clicking Catalog on the Operation menu.
  • Next, load the backup set catalog by clicking on the appropriate backup set folder. (question marks turn to + signs when the catalogs are loaded and a red x indicates a corrupted file).
  • Check all the backup sets that you wish to restore, or even individual files and folders within a backup set.
  • Click Restore.
  • Select the drive to restore to, this can be different from the original. You can restore the local registry, the file permissions and you can choose to verify after restore has occurred.
  • You can create a log using Select Log Options for Full Detail or just a Summary.

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