How to enable debug mode for Plesk backup operations

Applicable to:

Logging of Plesk backup procedure is not detailed enough. How to increase its verbosity?

For backup tasks run from the Control Panel:

Nothing needs to be done. Logs are collected with the -debug switch by default for such tasks.
For scheduled backups:

To increase verbosity for scheduled backups parameter verbose_scheduled_backup_logs should be enabled in Plesk database:

MYSQL_LIN: replace into misc (param,val) values ('verbose_scheduled_backup_logs', 'true');

WARNING: As with any other log file, it is strongly recommended that you disable verbosity once you have finished troubleshooting the issue. Otherwise, you may quickly run out of free disk space, which will in turn lead to data loss and service downtime. Server performance will be affected as well. Run the following command to turn the verbosity off:

MYSQL_LIN: delete from misc where param='verbose_scheduled_backup_logs';
For command line pleskbackup utility:

Add one or more verbose -v options to the backup command.

For example, the below commands will back up the whole server with maximum verbosity in logs and the command line:

# /usr/local/psa/bin/pleskbackup server -vvvvv

On Windows, multiple verbose options cannot be joined and has to be specified separately:

C:\> "%plesk_cli%\\pleskbackup" --server -v -v -v -v -v