Il est possible d'utiliser le meme binaire mysql pour gérer plusieurs instances mysql sur des ports et/ou ip differentes sur le même serveur.

==Installation==
L'installation se fait via le systeme de paquet habituel
<pre># yum install mysql-server</pre>

Une fois installé nous allons crée les repertoires qui contiendront les nouvelles instances
<pre># mkdir -p /export/data/mysql_33023
# mkdir -p /export/data/mysql_33024</pre>

Puis nous allons faire des liens depuis /var/lib (optionnel car les chemins plus haut peuvent être défini en dur sur le fichier de configuration):
<pre># cd /var/lib
# ln -s /export/data/mysql_33023
# ln -s /export/data/mysql_33024</pre>

Enfin, nous allons installer les bases
<pre># mysql_install_db --user=mysql --datadir=/var/lib/mysql_33023/
# mysql_install_db --user=mysql --datadir=/var/lib/mysql_33024/</pre>

==Configuration==
Dans le fichier my.cnf
<source lang="text">
[mysqld_multi]
mysqld     = /usr/bin/mysqld_safe
mysqladmin = /usr/bin/mysqladmin
user       = multi_admin
password   = xxxxxxx
log        = /var/log/mysqld_multi.log

[mysqld33023]
socket     = /var/lib/mysql_33023/mysql.sock
port       = 33023
pid-file   = /var/lib/mysql_33023/mrs-prd-ossbdd-1.pid
datadir    = /var/lib/mysql_33023
language   = /usr/share/mysql/english
user       = mysql
mysqld     = /usr/libexec/mysqld
log-error  = /var/lib/mysql_33023/mrs-prd-ossbdd-1.err

[mysqld33024]
socket     = /var/lib/mysql_33024/mysql.sock
port       = 33024
pid-file   = /var/lib/mysql_33024/mrs-prd-ossbdd-1.pid
datadir    = /var/lib/mysql_33024
language   = /usr/share/mysql/english
user       = mysql
mysqld     = /usr/libexec/mysqld
log-error  = /var/lib/mysql_33024/mrs-prd-ossbdd-1.err
</source>

Il est possible de lancer les instances
<pre># mysqld_multi start 33023
# mysqld_multi start 33024</pre>

Enfin, il faut créer l'utilisateur multi_admin afin de lui permettre d'éteindre les instances. Nous allons aussi modifier l'utilisateur root
<pre># mysql -u root -S /var/lib/mysql_33023/mysql.sock -p
mysql> GRANT SHUTDOWN ON *.* TO 'multi_admin'@'localhost' IDENTIFIED BY 'xxxxxxx';
mysql> GRANT ALL PRIVILEGES ON *.* TO 'root'@'localhost' identified by "yyyyyyy" WITH GRANT OPTION;
mysql> flush privileges;
# mysql -u root -S /var/lib/mysql_33024/mysql.sock -p
mysql> GRANT SHUTDOWN ON *.* TO 'multi_admin'@'localhost' IDENTIFIED BY 'xxxxxxx';
mysql> GRANT ALL PRIVILEGES ON *.* TO 'root'@'localhost' identified by "yyyyyyy" WITH GRANT OPTION;
mysql> flush privileges;</pre>

Il est désormais possible d'éteindre les instances
<pre># mysqld_multi stop 33023
# mysqld_multi stop 33024</pre>

==Lancement au boot==
Copier le scripts dans /etc/init.d/mysqld_multi.server
<source lang="bash">
#!/bin/sh
#
# A simple startup script for mysqld_multi by Tim Smith and Jani Tolonen.
# This script assumes that my.cnf file exists either in /etc/my.cnf or
# /root/.my.cnf and has groups [mysqld_multi] and [mysqldN]. See the
# mysqld_multi documentation for detailed instructions.
#
# This script can be used as /etc/init.d/mysql.server
#
# Comments to support chkconfig on RedHat Linux
# chkconfig: 2345 64 36
# description: A very fast and reliable SQL database engine.
#
# Version 1.0
#

basedir=/var/lib/mysql/mysql
bindir=/usr/bin/

if test -x $bindir/mysqld_multi
then
  mysqld_multi="$bindir/mysqld_multi";
else
  echo "Can't execute $bindir/mysqld_multi from dir $basedir";
  exit;
fi

case "$1" in
    'start' )
        "$mysqld_multi" start $2
        ;;
    'stop' )
        "$mysqld_multi" stop $2
        ;;
    'report' )
        "$mysqld_multi" report $2
        ;;
    'restart' )
        "$mysqld_multi" stop $2
        "$mysqld_multi" start $2
        ;;
    *)
        echo "Usage: $0 {start|stop|report|restart}" >&2
        ;;
esac</source>

On rajoute les droits d'execution.
Puis on test que toutes les instances se lancent et s'arrêtent correctement via le script :
<pre># /etc/init.d/mysqld_multi.server start
# /etc/init.d/mysqld_multi.server stop</pre>

Puis configurer chkconfig
<pre># chkconfig mysqld_multi.server on</pre>

==Administration==
===Lancement de l'instance 33024===
<pre># mysqld_multi start 33024</pre>
ou
<pre># /etc/init.d/mysqld_multi.server start 33024</pre>
===Extinction de l'instance 33024===
<pre># mysqld_multi stop 33024</pre>
ou
<pre># /etc/init.d/mysqld_multi.server stop 33024</pre>
===Status de l'instance 33024===
<pre># mysqld_multi report 33024</pre>
ou
<pre># /etc/init.d/mysqld_multi.server start 33024</pre>
===Connexion à l'instance 33024===
<pre># mysql -S /export/data/mysql_33024/mysql.sock -u root -p</pre>