Mysql Pre-4.1
mysqldump -u username -p password --quick [database [table1, table2, ...]] > backup_db.sql
4.1 and up
mysqldump -u username -p password [database [table1, table2, ...]] > backup_db.sql
Great for doing maintenance backups via cron, or just occasional dumps for off-site storage and archival.
And useful shorthand for the manual:
http://dev.mysql.com/doc/mysql/en/mysqldump.html
If this is the case, you may get around it by using the "--skip-opt" option, i.e.