To create daily backups of your database:

sudo vim /etc/cron.daily/backupgemstone

enter the following script into the editor:

#!/bin/sh

/opt/gemstone/product/seaside/bin/runBackup
cp /opt/gemstone/product/seaside/data/backups/extent0.dbf \
 /home/seasideuser/backups/extent-`date +"%Y%m%d"`.dbf

Then the backups directory:

mkdir ~/backups

You can change the frequency of the backups by creating the backup-script in one of: /etc/cron.monthly, /etc/cron.weekly/, /etc/cron.daily/, /etc/cron.hourly