I want to backup all the mysql databases in my server.

Could you told how can I do it via SSH?

Thanks

mysqldump -u root -p -A > backup.sql

MySQL Backup (http://worldcommunity.com/opensource/utilities/mysql_backup.html).

Better gzip it
mysqldump --opt -u username -p -A | gzip > /path/to/writable/directory/dbsdump.gz