Export and Import all MySQL databases at one time

I want to keep a backup of all my MySQL databases. I have more than 100 MySQL databases. I want export all of them them at the same time and again import the all of them into my MySQL server at one time. How can I do that?

Export: mysqldump -u root -p --all-databases > alldb.sql   Look up the documentation for mysqldump. You may want to use some of the options mentioned in comments:   mysqldump -u root -p --opt --all-databases > alldb.sql   mysqldump -u root -p --all-databases --skip-lock-tables > alldb.sql Import: mysql -u root -p < alldb.sql