MySQL Migration from Slave to Master

Question

I recently had a problem with our server. It required us to install a new hard drive, cpanel, and setup the old hard drive as a slave. How can I migrate the mysql database from the slave drive to the master drive? The slave contains the tables with MYD, MYI, and frm files. The database is probably about 20G.

I'm assuming SSH is the best way to do this. I am not very familiar with SSH commands and cannot find out how to do this. I've already setup the new database (on the fresh install on the master drive) with the same name, users, and passwords.

System: Linux, Centos 6.4

Answer 1

I was left wondering because you mentioned SSH which implied connecting from your database server to a different machine (free tip: You use "SSH" to connect to a machine, but the things you type after that are "shell commands", not "SSH commands." I googled that phrase just now and was horrified at how frequently they're improperly called "SSH commands") ... and in Sqlbot's world, a "slave" is a different machine -- a replication slave -- which also was initially confusing.

You mentioned MYD and MYI files but not IBD files, so either you are using MyISAM and not InnoDB, or you're using a mix but you never set innodb_file_per_table = 1.

Your path to recovery depends on whether you are using InnoDB.

If you're not using InnoDB, then you can -- believe it or not -- just copy the old database directories and files into place and fix the permissions if needed. MySQL is extremely forgiving about this with MyISAM tables.

Connect to your MySQL server and locate the data directory. From an old CentOS machine of mine (probably still the same for you):

mysql> show variables like 'datadir';
+---------------+-----------------+
| Variable_name | Value           |
+---------------+-----------------+
| datadir       | /var/lib/mysql/ |
+---------------+-----------------+
1 row in set (0.00 sec)

Find the comparable directory on your old hard drive, and copy all of the directories -- but not the files, and not the "mysql" directory -- into your datadir (probably /var/lib/mysql).

Then, if the files aren't owned by the "mysql" user,

root@host# chown -R mysql:mysql /var/lib/mysql

Then see if it worked.

mysql> SHOW DATABASES;

If you are using MyISAM only, your databases and tables should be on the new server, though you will need to do CHECK TABLES on all of your tables or use the mysqlcheck utility to verify that they are all intact and repair them as needed.

If you're using InnoDB, the steps will be different, so see if this works for you.