Here are some sample commands you could use to backup your database, depending on what database system you're using. You may have to modify these commands for your particular setup. Replace the $VARIABLEs with appropriate values for your setup.
mysqldump --max-allowed-packet=32M -u $USERNAME -p $DATABASENAME > backup.sql
The value for max-allowed-packet should be the value you've set in
your MySQL configuration file, and should be larger than the
largest attachment in your database. See the
for more information on
pg_dump --no-privileges --no-owner -h localhost -U $USERNAME > bugs.sql