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If you need master-master replication for your MySQL server. This example is for Centos 6 x64 but on other Linux OS the process is similar.

For example we have two following servers with IPs:
1.1.1.1 SERVER_A
2.2.2.2 SERVER_B

1. Install MySQL server on both servers.yum -y install mysql-server
2. By default, MySQL works only with localhost (127.0.0.1), so we need to edit MySQL config file /etc/my.cnf and add followingon SERVER_A:
   server-id = 1
bind-address = 1.1.1.1
log_bin = /var/log/mysql/mysql-bin.log
binlog_do_db = database_for_replication
#replicate-do-table = database_for_replication.table_for_replication (You can replicate only some table(s))on SERVER_B:
   server-id = 2
bind-address = 2.2.2.2
log_bin = /var/log/mysql/mysql-bin.log
binlog_do_db = database_for_replicationAfter changes – restart mysql on both servers /etc/init.d/mysql restart
   
3. Create MySQL user for replication on BOTH servers (use command mysql to enter MySQL console).
   grant all privileges on *.* to replication_username@'%' identified by "some_password";
flush privileges;
   Note:
   *.* means you grant access to ALL databases, if you need to grant access only to some database, change it -> some_db.* , or some table -> some_db.some_table
   ‘%’ means you grant access to ALL IPs, if you need to grant access only to some IP, change it -> ‘111.222.333.444’
4. Next step, log into SERVER_A into MySQL console, and execute:

   show master status;
   
   the result will be similar to:
   +-------------------+----------+---------------------------+------------------+
   | File              | Position | Binlog_Do_DB              | Binlog_Ignore_DB |
   +-------------------+----------+---------------------------+------------------+
   | mysqld-bin.000005 | 49572095 | database_for_replication  |                  |
   +-------------------+----------+---------------------------+------------------+
   1 row in set (0.00 sec)
   
   REMEMBER THIS RESULT, YOU'LL NEED IT IN STEP 5

5. Log into SERVER_B into MySQL console, execute:slave stop;
change master to master_host='1.1.1.1', master_user='replication_username', master_password='some_password', master_log_file='mysqld-bin.000005', master_log_pos=49572095;
slave start;
6. Next step, log into SERVER_B into MySQL console, and execute:

   show master status;
   
   the result will be similar to:
   +-------------------+----------+---------------------------+------------------+
   | File              | Position | Binlog_Do_DB              | Binlog_Ignore_DB |
   +-------------------+----------+---------------------------+------------------+
   | mysqld-bin.000001 | 98748451 | database_for_replication  |                  |
   +-------------------+----------+---------------------------+------------------+
   1 row in set (0.00 sec)
   
   REMEMBER THIS RESULT, YOU'LL NEED IT IN STEP 7

7. Log into SERVER_A into MySQL console, execute:slave stop;
change master to master_host='2.2.2.2', master_user='replication_username', master_password='some_password', master_log_file='mysqld-bin.000001', master_log_pos=98748451;
slave start;THAT’S IT, YOUR MYSQL CLUSTER READY