I'm currently using this to manually back up databases:

mysqldump --single-transaction --quick user_db | gzip > /backup/user_db.sql.gz

I have several databases on the server, so I currently run it once for each database, changing "user_db" to the name of each database. The whole process takes about 1 1/2 hours, so I only do it once a week.

I'd like to set up a CRON to back them all up automatically and keep them in their own .sql.gz files, so I can have it done nightly without me babysitting it.

Does this look right?

for DB in $(mysql -e 'show databases' -s --skip-column-names); do
  mysqldump --single-transaction --quick $DB | gzip > "/backup/$DB.sql.gz";
done

I have VERY little experience with cron, so I'm only guessing that (assuming the code is good) I can add this using "crontab -e".

It feels like my MySQL is held together with bubble gum and prayers, so I'm always very hesitant to run something unless I'm 100% positive that it'll work flawlessly :-O I'm not in a position where I can just "run it and see" if a potential typo could crash everything, ya know?