Backing up via the command line:
Type the following at the prompt with the appropriate USERNAME and DATABASE name:
mysqldump -u USERNAME -p DATABASE > dump.sql
You will be prompted for your database password and then the DATABASE will be dumped to a plain-text file called dump.sql.
Restoring via the command line:
First drop and recreate the database as needed:
Drop the database
mysqladmin -u USERNAME -p drop DATABASE
Recreate the database
mysqladmin -u USERNAME -p create DATABASE
Import the backup data
mysql -u USERNAME -p DATABASE < dump.sql