Is it possible to READ LOCK all databases and then UNLOCK one by one? I need to take backup of databases from a live server for replication. There could be 2-5 databases each having size of 1-5 GB. Master is a live server so I can not stop mysql service. Since size of data is big, baking up in Read-Only mode could be dangerous too. I'm wondering is it possible to 

1. READ LOCK all databases and stop bin-log writing
2. Take backup of a database and UNLOCK only that one.

MySQL Version   : 5.1.61
Storage Engine  : MyISAM

Thanks in advance.
If you already have a Slave hanging off the Master, STOP SLAVE and backup the Slave.

If you are trying to set up replication to begin with, you are out of luck because you are still on MyISAM.