A step by step guide to upgrading to MySQL 5.5

MySQL 5.5 has created a lot of hype and its not just hype, there are major performance enhancements not only in the MySQL server itself but in the newer InnoDB plugin shipped with MySQL 5.5. That’s exactly the reason why I have myself upgraded to MySQL 5.5 (The server running this blog run MySQL 5.5). Now since I haven’t come across a guide to help in upgrading to MySQL 5.5, I thought why not make one myself. So here goes nothing!

Download the binary

$ cd /root/
$ wget http://dev.mysql.com/get/Downloads/MySQL-5.5/mysql-5.5.11-linux2.6-i686.tar.gz/from/http://mysql.llarian.net/
$ mv index.html mysql-5.5.8-linux2.6-i686.tar.gz

Backup the MySQL configuration

$ mkdir /root/mysql-5.1-conf
$ cp -R /etc/mysql/ /root/mysql-5.1-conf

Backup the data directory

We will be backing up the data in the form of SQL dump as well as by copying the data files over to a safe place, just to be 100% sure about the data not getting lost.

$ mkdir /root/mysql-5.1-data
$ cp -R /var/lib/mysql/ /root/mysql-5.1-data

Backup the data as SQL dump

Backup the mysql database separately and not with all the other databases, because we are going to need it before we restore all the databases.

$ mkdir /root/mysql-5.1-dump
$ mysqldump -u user_name -p --databases mysql > /root/mysql-5.1-dump/mysql.sql
$ mysqldump -u user_name -p --databases db_name > /root/mysql-5.1-dump/db_name.sql

Install the asynchronous I/O library

This is so that we can take advantage of the asynchronous I/O capability in the new InnoDB plugin that ships with MySQL 5.5

$ apt-get install libaio-dev

Untar the archive

$ tar xzvf mysql-5.5.8-linux2.6-i686.tar.gz

Copy or move the untarred MySQL directory to the installation directory

$ cp -R mysql-5.5.8-linux2.6-i686 /usr/local/
$ cd /usr/local/
$ ln -s mysql-5.5.8-linux2.6-i686 mysql

Remove the older version of MySQL

Now is the time to remove the older version of MySQL, in this case I assume the older version to be MySQL 5.1

$ apt-get remove mysql-server-5.1
$ apt-get autoremove
$ apt-get remove mysql-client
$ apt-get autoremove

Add the path to MySQL bin directory to the PATH variable

$ vim /etc/environment

Set the correct file and directory permissions on the MySQL installation directory

Setting correct permissions is very important, make sure that all the files except those under the data directory are owned by root. The data directory has to be owned by the user mysql.

$ cd /usr/local/mysql
$ chown -R mysql:mysql data

Create the socket directory

Here again, setting the correct permissions on the socket directory is very important, otherwise MySQL would not run.

$ mkdir /var/run/mysqld/
$ chown -R mysql:mysql /var/run/mysqld/

Copy the sample MySQL configuration file to the etc directory and setup the paths

$ cd /usr/local/mysql/support-files/
$ cp my-large.cnf /etc/my.cnf

Now edit /etc/my.cnf so that it has the following values:

user            = mysql
socket          = /var/run/mysqld/mysqld.sock
port            = 3306
basedir         = /usr/local/mysql
datadir         = /usr/local/mysql/data
tmpdir          = /tmp
log_error       = /var/log/mysql/error.log

Copy the MySQL server startup script to the startup directory

The MySQL startup script has to be placed in the directory where all the startup scripts reside, so that MySQL starts on system startup. Make sure that you make the startup script executable, and update the rc.d database to notify the system about the presence of a new startup script.

$ cd /usr/local/mysql/support-files/
$ cp mysql.server /etc/init.d/mysql
$ chmod +x /etc/init.d/mysql
$ update-rc.d mysql defaults

Remove the MySQL files from the older version

Make sure you don’t delete files belonging to the new version we are installing.

$ rm -R /var/lib/mysql
$ rm -R /etc/mysql
$ rm -R /usr/lib/mysql

When starting the MySQL server for the first time after the new installation, it has to be started without the grants table, for two reasons. Firstly, because we want to retain the users and privileges data from the previous install of MySQL and secondly, because the schema of the grants table in MySQL 5.5 has changed.
So what we will do is start MySQL without the grants table, import the users and privileges data we backed up earlier in this guide and run the mysql_upgrade script that modifies the schema of the grants table to be in sync with that in MySQL 5.5. After that we will be able to run MySQL normally and have all the users and privileges same as in the previous version we had.

Start MySQL server without grants table.

$ mysqld --skip-grant-tables --user=mysql

Load the MySQL users and privileges data we backed up earlier

$ cd /root/mysql-5.1-backup/dump/
$ mysql < mysql.sql

Run the upgrade script so that everything gets upgraded to the version 5.5

$ mysql_upgrade

Stop the server and start it normally

$ /etc/init.d/mysql stop
$ /etc/init.d/mysql start

There you go, you have a MySQL 5.5 server up and running in no time! Do share your thoughts if you try out MySQL 5.5

UPDATE: This article is translated to Serbo-Croatian language by Anja Skrba from Webhostinggeeks.com.