Chris Paquin

AI, Virtualization, Containers, Infrastructure, Linux

Category: mysql

  • Install Mysql Server on Centos 5 and Setup Root Password

    Dolphin-cartoon

    Oops, needed mysql server installed in order to install Zenoss on a centos 5 vm.

    First lets do the following…

    #yum install php-mysql mysql mysql-server

    #/sbin/chkconfig mysqld on
    #/etc/init.d/mysqld start

    To set the password run the following

    #mysqladmin -u root password NEWPASSWORD

    If you need to change it, use the command below

    #mysqladmin -u root -p’oldpassword’ password newpass

  • Fixing Mysql Replication on RHEL/CentOS

    Mysql Oh crap, replication between my media wiki server in datacenter 1 and in datacenter 2 has for some reason stopped working.

    Logging into the slave server,  I was able to verify this was in fact by typing the following and looking for the two SLAVE specific lines.

    mysql> show slave status \G

    Slave_IO_Running: No
    Slave_SQL_Running: No

    So I stopped the slave with the following command. Note that this does not stop the database, rather it just stops the slave from attempting to replicate

    mysql> stop slave;

    Then go onto the master and get the current log file and log file position. This information is used later to sync the slave with the master.

    mysql> show master status \g

    mysql-bin.000004 | 90171568

    Now freeze the master.

    mysql> flush tables with read lock; (dont close this window)

    Then in a new console on the master and dump out the database.

    mysqldump –all-databases –lock-all-tables >dbdump.db

    scp the dump file to the slave server and import it.

    mysql < dbdump.db

    Then set the master configuration on the slave server using the command below from within the database.

    mysql> CHANGE MASTER TO
    -> MASTER_HOST='master_host_name',
    -> MASTER_USER='replication_user_name',
    -> MASTER_PASSWORD='replication_password',
    -> MASTER_LOG_FILE='recorded_log_file_name',
    -> MASTER_LOG_POS=recorded_log_position;

    Then start the slave.

    mysql> start slave;

    Then check the slave status again and look for Yes in the two Slave lines.

    mysql> show slave status \G

    Slave_IO_Running: Yes
    Slave_SQL_Running: Yes

    In my case I was able to verify that all changes from my master wiki replicated to the slave wiki.