Backup

$ mysqldump --add-drop-table --single-transaction -u _root_ -p_password_ koha > 2008-11-11_koha.sql
$ mysqldump --add-drop-table -u _root_ -p_password_ koha issues > 2008-11-11_koha.issues.sql

http://www.nabble.com/Backing-up-3.0-to21076508.html

Restore
$ mysql -u root -p_password_ koha < koha.sql
$ mysql -u root -p_password_ koha.issues < koha.issues.sql