SQL Server¶

SQL Server doesn't need any client tools. The agent runs BACKUP DATABASE / BACKUP LOG ... TO DISK over its built-in driver, SQL Server writes the files, and the agent moves them into its spool, uploads them as db.pxar and deletes them. That means every fallbck-agent reports mssql. The normal setup is the agent on the SQL Server box itself, either the Windows service or the Linux package.

Job options¶

• Mode
  • auto: does a full when there isn't one, when the chain broke, or when the last full is older than full every N days. Otherwise a differential.
  • full, differential
  • log: transaction log only. Run it as its own job on a tight schedule.
• Also back up the log after each full/differential, for databases in FULL or BULK_LOGGED recovery.
• Compression: off by default. PBS dedups uncompressed backups way better, and Express can't compress anyway.
• Copy-only.

master always gets a full and tempdb never gets backed up. Offline databases and snapshots are skipped, with a note in the run.

Keeping the chain honest¶

The agent tracks the chain it holds for each database (last full, last diff, logs since) and checks it against msdb before every run:

• If the server's newest full isn't the one FallBCK holds (another tool took one, or a run died after the backup), the next diff becomes a full. That's a chain reset.
• If a log backup doesn't start where the previous one ended, it's flagged as a log chain gap.

The run page lists every backup set with its LSNs and why it got that type.

Where the files go¶

By default they go to the instance's default backup path (InstanceDefaultBackupPath). SQL Server can write there, and an agent on the same host can read it.

If SQL Server runs somewhere else or in a container, give both views of one shared directory:

• backup_dir: the path as SQL Server sees it
• agent_dir: the same place as the agent sees it (UNC share, bind mount)

Before any backup runs, the agent writes a probe file to check that the two really are the same place.

Auth¶

• SQL login: password on the job or in a credential profile.
• Windows integrated auth: leave the user blank on Windows and the agent connects as its service account. LocalSystem needs a login with backup rights, e.g. db_backupoperator in every database, or sysadmin.

There's no passwordless option for SQL Server on Linux. Use host\instance for named instances.

Restore¶

The restore commands in the manifest give you the chain in order:

1. RESTORE DATABASE ... WITH NORECOVERY for the full and the newest differential
2. RESTORE LOG ... for each log backup
3. finish WITH RECOVERY. Add STOPAT for point-in-time.