Undocumented Ntbackup Registry Keys

In Windows NT 4.0, I found some undocumented Ntbackup-related Registry keys. I haven't discovered official documentation for what each key does, but I used a trial-and-error approach to explore some of the more obvious ones, and I share my discoveries for readers who would like to add these keys to their arsenal. You can find the settings under the HKEY_CURRENT_USER\Software\Microsoft\Ntbackup\User Interface Registry key.

  • Auto Verify Backup. This key, which has a default value of 0, determines whether Ntbackup will verify your backups when you perform them. You can override this value in the Backup Wizard at runtime.
  • Backup Catalogs. This key has a default value of 0. If you change the value to 1, Ntbackup will back up all catalog files from your Temp directory every time you perform a backup. Ntbackup will still delete the catalog files when it closes but will save them on tape first.
  • Eject Tape Flag. By default, this key has a value of 0. If you change the value to 1, Ntbackup will eject the media each time Ntbackup closes.
  • Skip Open Files. By default, Ntbackup will try for 30 seconds to back up an open file. Thirty seconds is plenty of time to close any application that might be using the file. However, NT keeps more than 10 system files (e.g., the Registry, event logs) open at all times. If Ntbackup spends 30 seconds trying to back up each open system file, your backup can easily take an extra 5 to 10 minutes. Changing this key's value to 1 lets Ntbackup skip open files altogether.
  • Wait Time. This key sets the number of seconds that Ntbackup will spend trying to back up an open file before timing out. I usually leave the Skip Open Files key set to 0 and change the value of Wait Time to 5. This combination of values doesn't delay Ntbackup long while it tries to close system files, and it gives me a chance to close applications that have files open.

The names of some other keys also imply a connection to Ntbackup. If you experiment with Registry keys, be sure to take the proper precautions. Don't experiment on any machine that you can't afford to reformat. I also recommend using the Export Registry File option in regedit.exe. This option lets you create an "undo" file. The option exports a key you select to a .reg file, and you can import the unaltered key back into the Registry if need be.

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