MySQL
-----
-:command:`mysqldump --opt -u $USERNAME -p $DATABASENAME > backup.sql`
+:command:`mysqldump --max-allowed-packet=32M -u $USERNAME -p $DATABASENAME > backup.sql`
-See the
+The value for :command:`max-allowed-packet` should be the value you've set in
+your :ref:`MySQL configuration file <mysql>`, and should be larger than the
+largest attachment in your database. See the
`mysqldump documentation <http://dev.mysql.com/doc/mysql/en/mysqldump.html>`_
for more information on :file:`mysqldump`.