Each slave must connect to the master using a standard MySQL username and password, so there must be a user account on the master that the slave can use to connect. Any account can be used for this operation, providing it has been granted the REPLICATION SLAVE privilege.

You do not need to create a specific user for replication. However, you should be aware that the username and password will be stored in plain text within the master.info file. Therefore, you may want to create a user that only has privileges for the replication process.

To create a user or grant an existing user the privileges required for replication, use the GRANT statement. If you create a user solely for the purposes of replication then that user needs only the REPLICATION SLAVE privilege. For example, to create a user, repl, that can connect for replication from any host within the mydomain.com domain, issue this statement on the master:

mysql> GRANT REPLICATION SLAVE ON *.*
    -> TO 'repl'@'%.mydomain.com' IDENTIFIED BY 'slavepass';

See Section 12.5.1.3, “GRANT Syntax”, for more information on the GRANT statement.

You may wish to create a different user for each slave, or use the same user for each slave that needs to connect. As long as each user that you want to use for the replication process has the REPLICATION SLAVE privilege you can create as many users as you require.