After being unable to Stop after Upload a backup job in Duplicati on a QNAP, forcing the job to Stop was necessary. This locked the database and restarting the backup job was impossible. This was the resulting error message:

The database file is locked.

The Duplicati Forum was the last resort for help.

Resolve Locked Database

  1. Export the backup job as a file or to command line
  2. Search for the dpath entry

  3. Use lsof to find the processes locking the database

    lsof "/share/CACHEDEV1_DATA/.qpkg/Duplicati/.config/Duplicati/PJISXRFXEA.sqlite"

    • The output shows you the process and the process IDs, which can be used to restart or kill the service

        COMMAND     PID  USER   FD   TYPE DEVICE  SIZE/OFF      NODE NAME
  mono-sgen 23142 admin   22ur  REG  252,0 425369600 110105363 PJISXRFXEA.sqlite
  mono-sgen 23142 admin   24ur  REG  252,0 425369600 110105363 PJISXRFXEA.sqlite
  mono-sgen 23142 admin   29ur  REG  252,0 425369600 110105363 PJISXRFXEA.sqlite
  4. Restart the services locking the database
  5. Rerun the backup job

Able to start the backup again, it ended with another error giving me a list of files stored on the remote location. The backup was not successful, repairing the database for the backup job was my next best guess - which resulted in another error.

2018-06-11 13:25:17 +02 - [Error-Duplicati.Library.Main.Operation.RepairHandler-CleanupMissingFileError]: Failed to perform cleanup for missing file: duplicati-b58bcb8fcefe141a2ba3a92aea3497758.dblock.zip.aes, message: Repair not possible, missing 582 blocks.

If you want to continue working with the database, you can use the "list-broken-files" and "purge-broken-files" commands to purge the missing data from the database and the remote storage.

The hint in the error message led me to the two additional comments I could use to work around the error and get the backup job running again.

List and Purge Broken Files

  1. Export the backup job to command line
  2. Replace the backupcommand with list-broken-files and/or purge-broken-files respectively.
    • Command Line example on a QNAP

    /opt/Qmono/bin/mono /share/CACHEDEV1_DATA/.qpkg/Duplicati/Duplicati/Duplicati.CommandLine.exe purge-broken-files "ssh://172.16.10.10:22//mnt/data/?auth-username=user&auth-password=user&ssh-fingerprint=ssh-rsa%" --backup-name=data --dbpath=/share/CACHEDEV1_DATA/.qpkg/Duplicati/.config/Duplicati/PJISXRFXEA.sqlite

  3. Rerun the backup itself

If you run into some weird errors, or the backup is still not working rerun repair,list-broken-files and purge-broken-files with the additional option --no-backend-verification. Also rerun the backup itself with the switch set to true one time after doing the above. This is some kind of weird user experience problem of duplicati, which was discussed at Error on purge-broken-files already.