Define different retention schedules

If you want to manage backup retention on different schedules, the most straight forward approach is to define a dedicated configuration for retention rule using a different prefix in the BACKUP_FILENAME parameter and then run them on different cron schedules.

For example, if you wanted to keep daily backups for 7 days, weekly backups for a month, and retain monthly backups forever, you could create three configuration files and mount them into /etc/dockervolumebackup/conf.d:

# 01daily.conf
BACKUP_FILENAME="daily-backup-%Y-%m-%dT%H-%M-%S.tar.gz"
# run every day at 2am
BACKUP_CRON_EXPRESSION="0 2 * * *"
BACKUP_PRUNING_PREFIX="daily-backup-"
BACKUP_RETENTION_DAYS="7"

# 02weekly.conf
BACKUP_FILENAME="weekly-backup-%Y-%m-%dT%H-%M-%S.tar.gz"
# run every monday at 3am
BACKUP_CRON_EXPRESSION="0 3 * * 1"
BACKUP_PRUNING_PREFIX="weekly-backup-"
BACKUP_RETENTION_DAYS="31"

# 03monthly.conf
BACKUP_FILENAME="monthly-backup-%Y-%m-%dT%H-%M-%S.tar.gz"
# run every 1st of a month at 4am
BACKUP_CRON_EXPRESSION="0 4 1 * *"

While it’s possible to define colliding cron schedules for each of these configurations, you might need to adjust the value for LOCK_TIMEOUT in case your backups are large and might take longer than an hour.