MySQL Replication

Server 1 my.cnf

[mysqld]
datadir=/var/lib/mysql
socket=/var/lib/mysql/mysql.sock  
# Default to using old password format for compatibility with mysql 3.x
# clients (those using the mysqlclient10 compatibility package).
old_passwords=1

bind-address = 0.0.0.0

binlog-do-db = mor
server-id = 10
auto_increment_increment = 10
auto_increment_offset = 1
master-host = 111.111.111.111
master-user = rep1
master-password = rep1
master-port = 3306
master-connect-retry = 60
replicate-do-db = mor
log-bin = /var/lib/mysql/mysql-bin.log
log-bin-index = /var/lib/mysql/master-log-bin.index
relay-log = /var/lib/mysql/slave-relay.log
relay-log-index = /var/lib/mysql/slave-relay-log.index
#slave-skip-errors=all

[mysql.server]
user=mysql
basedir=/var/lib

[mysqld_safe]
log-error=/var/lib/mysql/mysqld.log
pid-file=/var/run/mysqld/mysqld.pid

Server 2 my.cnf

[mysqld]
datadir=/var/lib/mysql
socket=/var/lib/mysql/mysql.sock  
# Default to using old password format for compatibility with mysql 3.x
# clients (those using the mysqlclient10 compatibility package).
old_passwords=1

bind-address = 0.0.0.0

binlog-do-db = mor
server-id = 20
auto_increment_increment = 20
auto_increment_offset = 2
master-host = 222.222.222.222
master-user = rep2
master-password = rep2
master-port = 3306
master-connect-retry = 60
replicate-do-db = mor
log-bin = /var/lib/mysql/mysql-bin.log
log-bin-index = /var/lib/mysql/master-log-bin.index
relay-log = /var/lib/mysql/slave-relay.log
relay-log-index = /var/lib/mysql/slave-relay-log.index
#slave-skip-errors=all  

[mysql.server]
user=mysql
basedir=/var/lib

[mysqld_safe]
log-error=/var/lib/mysql/mysqld.log
pid-file=/var/run/mysqld/mysqld.pid

Log files

In order for MySQL Replication to function properly you need to check log files in /var/lib/mysql

Open master-log-bin.index, it should contain names of the files which really exist in same folder. If there's some mismatch - edit this file: enter missing names for files or delete file names which does not represent real files in this folder.

Same with file slave-relay-log.index

Testing

Login to MySQL console on both servers:

mysql -u root -p 

Then:

SHOW SLAVE STATUS\G

If everything is ok you should see such lines between others on both servers:

Slave_IO_State: Waiting for master to send event
Slave_IO_Running: Yes

If Replication is off you will see:

Slave_IO_State:
Slave_IO_Running: No

Troubleshooting

Check file: /var/lib/mysql/mysqld.log

[ERROR] Got fatal error 1236: 'Could not find first log file name in binary log index file' from master when reading data from binary log

We go to the master and check /var/lib/mysql/master-log-bin.index file.

For example it can show:

/var/lib/mysql/mysql-bin.000001
/var/lib/mysql/mysql-bin.000002
/var/lib/mysql/mysql-bin.000003
/var/lib/mysql/mysql-bin.000005

In /var/lib/mysql/ we also have file mysql-bin.000004, so its' name is missing in index file, lets add it, so master-log-bin.index looks like:

/var/lib/mysql/mysql-bin.000001
/var/lib/mysql/mysql-bin.000002
/var/lib/mysql/mysql-bin.000003
/var/lib/mysql/mysql-bin.000004
/var/lib/mysql/mysql-bin.000005

Restart mysql on this server and try with slave again.

This is just an example - some other files records can be missing (or not existing be in file). Make sure file has all related files which are in same folder.