Linode snapshot - WordPress
Here's a guide on MySQL backups:
Assuming your database isn't too large, you can consider setting up a cron job to create backup dumps on a schedule consistent (but before) your backups.
mysqldump will do a table/row lock to make sure no other processes can add data during that time.
I'm a fan of automysqlbackup. It'll do the dirty work of dumping databases for you and rotating the backups. It's handy in case you get hacked or more likely bork something yourself (or a client) and need to go back to yesterday's data for example without having to restore a linode snapshot backup.