How to Set Up MySQL Master‑Slave Replication with Docker in Minutes

Build the Dockerfile

Start from the official MySQL 5.7 image, expose port 3306, copy a custom my.cnf configuration file, and set the default command to start MySQL:

FROM mysql:5.7
EXPOSE 3306
COPY my.cnf /etc/mysql/
CMD ["mysqld"]

Prepare my.cnf by first launching a temporary MySQL container, copying the default configuration, and then editing the file to enable binary logging, set a unique server-id, and comment out bind-address so remote connections are allowed. Key options include:

#bind-address    = 127.0.0.1   # comment to allow remote access
log-bin = /var/log/mysql/mysql-bin.index
server-id = 1   # master, change to 2 for slave

Directory layout

Create two parallel directories, one for the master and one for the slave, each containing its own Dockerfile and my.cnf (the slave’s server-id should be 2):

master/
├── Dockerfile
└── my.cnf

slave/
├── Dockerfile
└── my.cnf

Build the images

From each directory run:

docker build -t master/mysql:5.7.20 .   # in master/
docker build -t slave/mysql:5.7.20 .    # in slave/

Run the containers

Start the master and slave containers, linking the slave to the master so it can resolve the hostname master:

# Master
docker run -p 3306 --name mysql-master -e MYSQL_ROOT_PASSWORD=root -d master/mysql:5.7.20

# Slave
docker run -p 3306 --name mysql-slave --link mysql-master:master -e MYSQL_ROOT_PASSWORD=root -d slave/mysql:5.7.20

Use docker ps to verify the containers are running and note the host ports assigned.

Create replication user on the master

Enter the master container and execute:

mysql -uroot -proot
GRANT REPLICATION SLAVE ON *.* TO 'user'@'%' IDENTIFIED BY 'mysql';
GRANT SELECT, REPLICATION SLAVE ON *.* TO 'user'@'%';

Then obtain the binary‑log file and position: SHOW MASTER STATUS\G Typical output shows File: mysql-bin.000003 and Position: 154.

Configure the slave

Inside the slave container run:

CHANGE MASTER TO
  MASTER_HOST='master',
  MASTER_PORT=3306,
  MASTER_USER='user',
  MASTER_PASSWORD='mysql',
  MASTER_LOG_FILE='mysql-bin.000003',
  MASTER_LOG_POS=154;

Start replication and verify:

START SLAVE;
SHOW SLAVE STATUS\G

Key fields Slave_IO_Running and Slave_SQL_Running should both be Yes.

Shell script to automate the whole process

The following Bash script performs the steps above in about one minute. Adjust the paths to your custom my.cnf files as needed.

#!/bin/bash
MASTER_DIR=/var/lib/mysql/mysql-master
SLAVE_DIR=/var/lib/mysql/mysql-slave

# Remove old containers and data directories
docker rm -f mysql-master mysql-slave
rm -rf $MASTER_DIR $SLAVE_DIR

# Start fresh containers
docker run -p 3306 --name mysql-master -v /etc/master.cnf:/etc/mysql/my.cnf -v $MASTER_DIR:/var/lib/mysql -e MYSQL_ROOT_PASSWORD=root -d master/mysql:5.7.20
docker run -p 3306 --name mysql-slave -v /etc/slave.cnf:/etc/mysql/my.cnf -v $SLAVE_DIR:/var/lib/mysql -e MYSQL_ROOT_PASSWORD=root --link mysql-master:master -d slave/mysql:5.7.20

# Give containers time to initialize
sleep 3

# Create replication user on master
docker exec -it mysql-master mysql -uroot -proot -e "CREATE USER 'users'@'%' IDENTIFIED BY 'mysql'; GRANT REPLICATION SLAVE ON *.* TO 'users'@'%';"

# Capture master status
master_status=$(docker exec -it mysql-master mysql -uroot -proot -e "SHOW MASTER STATUS\G")
master_log_file=$(echo "$master_status" | awk 'NR==2{print $2}')
master_log_pos=$(echo "$master_status" | awk 'NR==3{print $2}')

# Configure slave
docker exec -it mysql-slave mysql -uroot -proot -e "CHANGE MASTER TO MASTER_HOST='master',MASTER_PORT=3306,MASTER_USER='users',MASTER_PASSWORD='mysql',MASTER_LOG_FILE='$master_log_file',MASTER_LOG_POS=$master_log_pos;"

docker exec -it mysql-slave mysql -uroot -proot -e "START SLAVE;"

docker exec -it mysql-slave mysql -uroot -proot -e "SHOW SLAVE STATUS\G"

Running this script sets up a fully functional MySQL master‑slave replication environment using Docker.