xtrabackup exit codes

The xtrabackup binary exits with the traditional success value of 0 after a backup when no error occurs. If an error occurs during the backup, the exit value is 1.

In certain cases, the exit value can be something other than 0 or 1, due to the command-line option code included from the MySQL libraries. An unknown command-line option, for example, will cause an exit code of 255.