Set up MySQL master-slave replication
Master-slave data replication allows for replicated data to be copied to multiple computers for backup and analysis by multiple parties. Needed changes identified by a group member must to be submitted to the designated “master” of the node. This differs from Master-Master replication, in which data can be updated by any authorized contributor of the group.
This article provides steps for setting up MySQL® master-slave database replication between two cloud servers. The operating system used for the examples in the article is CentOS® 6, built from a Rackspace Cloud Servers base image.
Before you begin
The steps in this article use two cloud servers,
Cloud servers have two IP addresses (one public, one private). The
examples demonstrate configuring replication over the private IP
interface so that no bandwidth charges are incurred. For the duration of
db01 is considered the master MySQL server (running in
read-write mode), and
db02 is considered the slave server (running in
If you already have a MySQL database running on the master node, a dump
and restore into the slave node is required before configuring
replication between them. You use the
mysqldump command to dump a
database into a file, then transfer it and restore it to the slave.
After the necessary configuration has been performed, replication is in
effect. For more information, see the Configure replication
Create the Cloud Servers
Create two Linux® cloud servers, using the Centos 6 base image. Use the following steps to create each server separately.
- Log in to the Cloud Control Panel.
- In the top navigation bar, click Select a Product then Rackspace Cloud.
- Select Servers then Cloud Servers.
- Click Create Server.
- Name the servers so that you can easily identify them during the setup.
- Select the Centos 6 base image.
- Select the RAM configuration (flavor) appropriate for your database requirements.
- Click Create Server.
The commands outlined in the following sections need to be executed by a privileged root or sudo group user. Any strings or values specified in brackets should be replaced with data specific to your setup.
You must install the mysql-server package on both CentOS cloud servers.
Before installing MySQL, confirm that the package database is up-to-date by running the following command:
Install MySQL and enable it to run at boot automatically:
#yum install mysql-server #chkconfig mysqld on
#service mysqld start
mysqldservice has been started, set your MySQL server root password by using following commands:
/usr/bin/mysqladmin -u root password 'new-password' /usr/bin/mysqladmin -u root -h web01 password 'new-password'
Note: Alternatively, you can run the secure installation script packaged with the MySQL installation:
# /usr/bin/mysql_secure_installation Enter current password for root (enter for none): ... Set root password? [Y/n] Y ... Remove anonymous users? [Y/n] Y ... Disallow root login remotely? [Y/n] Y ... Remove test database and access to it? [Y/n] Y ... Reload privilege tables now? [Y/n] Y
To permit connections on port 3306 (the
mysqlddefault port), add a TCP port 3306 rule with an insert at the last line number in the
RH-Firewall-1-INPUTchain (in this case, line 10):
# iptables -I RH-Firewall-1-INPUT 10 -p tcp --dport 3306 -j ACCEPT
Save the firewall configuration:
# service iptables save
Complete the following section to make relevant configuration changes to enable replication.
A MySQL user is required on the master server (
db01) to be used for
Run the following commands to set up the MySQL user, updating the entries in brackets with strings or values that you plan to use with your setup:
# mysql -u root -p mysql> grant replication slave on *.* TO [replication_username]@'[private IP of db02]' identified by '[some password]'; mysql> flush privileges; mysql> quit
Edit the /etc/my.cnf file, and add the following entries:
bind-address = 0.0.0.0 server-id = 1 log-bin = mysql-bin binlog-ignore-db = "mysql"
After you have finished updating the /etc/my.cnf file, restart the
#service mysqld restart
Before starting replication, the data on the master and slave servers must be the same. To accomplish this duplication, dump the data from the master (
db01) server and add it to the slave (
Use the following command to ensure that nothing can write to the master database during a database dump: Also note the filename and position of the binary log because you will need these values to complete the replication configuration on db02.
# mysql -u root -p mysql> FLUSH TABLES WITH READ LOCK; mysql> SHOW MASTER STATUS; +------------------+--------------------------+------------------+ | File | Position | Binlog_Do_DB | Binlog_Ignore_DB | +------------------+--------------------------+------------------+ | mysql-bin.000010 | 10 | | mysql | +------------------+--------------------------+------------------+ 1 row in set (0.00 sec)
Note: Record the filename and position of the binary log because you need these values to complete the replication configuration on
Perform a database dump by using
# mysqldump -u root -p --databases [database-1] [database-2] ... > /root/db_dump.sql
After the database dump has completed, lift the read lock from the master (
# mysql -u root -p mysql> UNLOCK TABLES;
Copy the database dump file to the slave server so that it can be restored by using the following command:
scp /root/db_dump.sql [private-IP-of-db02]:/root/
db02, edit the /etc/my.cnf file and add the following entries:
bind-address = 0.0.0.0 server-id = 2 master-host = [private-IP-of-db01] master-user = [replication-username] master-password = [replication-password] master-connect-retry = 60
Import the db_dump.sql file copied earlier and restart the MySQL service.
# mysql -u root -p < /root/db_dump.sql # service mysqld restart
Complete the slave replication steps:
# mysql -u root -p mysql> SLAVE STOP; mysql> CHANGE MASTER TO MASTER_HOST='[private-IP-of-db01]', MASTER_USER='[replication-username]', MASTER_PASSWORD='[replication-password]', MASTER_LOG_FILE='[file-listed-on-master-status]', MASTER_LOG_POS=[log-position-listed-on-master-status]; mysql> START SLAVE; mysql> SHOW SLAVE STATUS\G
Note: The Slave_IO_State field should show “Waiting for master to send event”. If it shows “Connecting to Master” please check your MySQL log file. By default it is /var/log/mysqld.log but it may be configured differently on your system. As always, /etc/my.cnf will define the location of your log file.
To test the replication setup, create a new database and associated
db01, and insert data to confirm that the changes are mirrored
db02. In the following example, the new database is named
testing and the new table is named users:
# mysql -u root -p mysql> create database testing; mysql> use testing mysql> create table users(id int not null auto_increment, primary key(id), username varchar(30) not null); mysql> insert into users (username) values ('foo'); mysql> insert into users (username) values ('bar'); mysql> exit
The changes should be visible on
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