On a replication slave, you must establish a unique server ID. If this has not already been done, this part of slave setup requires a server restart.
If the slave server ID is not already set, or the current value conflicts with the value that you have chosen for the master server, you should shut down your slave server and edit the configuration to specify a unique server ID. For example:
[mysqld] server-id=2
After making the changes, restart the server.
If you are setting up multiple slaves, each one must have a
unique server-id value that
differs from that of the master and from each of the other
slaves. Think of server-id values
as something similar to IP addresses: These IDs uniquely
identify each server instance in the community of replication
partners.
If you omit server-id (or set
it explicitly to its default value of 0), a slave refuses to
connect to a master.
You do not have to enable binary logging on the slave for replication to be enabled. However, if you enable binary logging on the slave, you can use the binary log for data backups and crash recovery on the slave, and also use the slave as part of a more complex replication topology (for example, where the slave acts as a master to other slaves).