How to Set Up MySQL Master-Slave Replication

This article will help you to setup master-slave replication between MySQL servers. We are using MySQL 5.5 on CentOS 6.3. I hope it will help you to setup replication.

Setup Details:

Master Server: 192.168.1.10
Slave  Server: 192.168.1.20
Database: mydb

If you are using different – different versions of MySQL on Master and Slave use this link to check compatibility.

1. Setup MySQL Master Server

• Create an mysql account on Master server with REPLICATION SLAVE privileges to which replication client will connect to master.

mysql> GRANT REPLICATION SLAVE ON *.* TO 'repl_user'@'192.168.1.20' IDENTIFIED BY 'secretpassword';
mysql> FLUSH PRIVILEGES;

• Block write statement on all the tables, so not changes made after taking backup.

mysql> use mydb;
mysql> FLUSH TABLES WITH READ LOCK;
mysql> exit;

• Edit MySQL configuration file and add the following lines under [mysqld] section.

# vim /etc/my.cnf

[mysqld]
log-bin=mysql-bin
binlog-do-db=mydb
server-id=1
innodb_flush_log_at_trx_commit=1
sync_binlog=1

• Restart master mysql server to changes take effect.

# service mysqld restart

• Check the current binary log file name (File) and current offset (Position) value using following command.

mysql > SHOW MASTER STATUS;
+------------------+----------+--------------+------------------+
| File             | Position | Binlog_Do_DB | Binlog_Ignore_DB |
+------------------+----------+--------------+------------------+
| mysql-bin.000002 |      107 | mydb         |                  |
+------------------+----------+--------------+------------------+

The above output is showing that the current binary file is using mysql-bin.000002 and offset value is 107. Note down these values to use on slave server.

• Take a backup of database and copy it to slave mysql server.

# mysqldump -u root -p mydb > mydb.sql
# scp mydb.sql 192.168.1.20:/opt/

• After completing backup remove the READ LOCK from tables, So that changes can be made.

mysql> UNLOCK TABLES;

2. Setup MySQL Slave Server

• Edit salve mysql configuration file and add following values under [mysqld] section.

# vim /etc/my.cnf

[mysqld]
server-id=2
replicate-do-db=mydb

server-id always be an non zero numeric value. These value will never be similar with other master and slave servers.

• Restart mysql slave server, If you had already configured replication use –skip-slave-start in start to not to immediate connect to master server.

# /etc/init.d/mysqld restart

• Restore database backup taken from master server.

# mysql -u root -p mydb < mydb.sql

• Setup option values on slave server using following command.

mysql>  CHANGE MASTER TO MASTER_HOST='192.168.1.10',
    -> MASTER_USER='repl_user',
    -> MASTER_PASSWORD='secretpassword',
    -> MASTER_LOG_FILE='mysql-bin.000002',
    -> MASTER_LOG_POS=107;

• Finally start the slave thread

mysql> SLAVE START;

• Check the status of slave server.

mysql> show slave status G

*************************** 1. row ***************************
               Slave_IO_State:
                  Master_Host: 192.168.1.15
                  Master_User: repl_user
                  Master_Port: 3306
                Connect_Retry: 60
              Master_Log_File: mysql-bin.000002
          Read_Master_Log_Pos: 107
               Relay_Log_File: mysqld-relay-bin.000001
                Relay_Log_Pos: 4
        Relay_Master_Log_File: mysql-bin.000002
             Slave_IO_Running: No
            Slave_SQL_Running: No
              Replicate_Do_DB: mydb
          Replicate_Ignore_DB:
           Replicate_Do_Table:
       Replicate_Ignore_Table:
      Replicate_Wild_Do_Table:
  Replicate_Wild_Ignore_Table:
                   Last_Errno: 0
                   Last_Error:
                 Skip_Counter: 0
          Exec_Master_Log_Pos: 107
              Relay_Log_Space: 107
              Until_Condition: None
               Until_Log_File:
                Until_Log_Pos: 0
           Master_SSL_Allowed: No
           Master_SSL_CA_File:
           Master_SSL_CA_Path:
              Master_SSL_Cert:
            Master_SSL_Cipher:
               Master_SSL_Key:
        Seconds_Behind_Master: NULL
Master_SSL_Verify_Server_Cert: No
                Last_IO_Errno: 0
                Last_IO_Error:
               Last_SQL_Errno: 0
               Last_SQL_Error:
  Replicate_Ignore_Server_Ids:
             Master_Server_Id: 1
1 row in set (0.00 sec)
mysql>

MySQL Master-slave Replication has been configured successfully on your system and in working mode. Thanks for using this tutorial, Kindly do not forgot to share it with your friends.