Ubuntu – How to downgrade thesql 5.7 to 5.6 on Ubuntu 16.04

16.04MySQL

I'm finding MySQL 5.7 to be a massive memory hog and want to roll back to MySQL 5.6.

However everytime I try to uninstall 5.7 and install 5.6 I end up with a MySQL service that won't start. Also I need to make sure I keep all of my databases.

Can anyone tell me a simple step by step on how to roll back mysql from 5.7 to 5.6?

**UPDATE**
$ dpkg -l | grep mysql    

rc  akonadi-backend-mysql                                1.13.0-2ubuntu4                                      all          MySQL storage backend for Akonadi  
ii  dbconfig-mysql                                       2.0.4ubuntu1                                         all          dbconfig-common MySQL/MariaDB support  
ii  libdbd-mysql-perl                                    4.033-1build2                                        amd64        Perl5 database interface to the MySQL database  
rc  libmysqlclient18:amd64                               5.6.30-0ubuntu0.15.10.1                              amd64        MySQL database client library  
rc  libmysqlclient18:i386                                5.6.30-0ubuntu0.15.10.1                              i386         MySQL database client library  
ii  libmysqlclient20:amd64                               5.7.12-0ubuntu1.1                                    amd64        MySQL database client library  
ii  mysql-client-5.7                                     5.7.12-0ubuntu1.1                                    amd64        MySQL database client binaries  
ii  mysql-client-core-5.7                                5.7.12-0ubuntu1.1                                    amd64        MySQL database core client binaries  
ii  mysql-common                                         5.7.12-0ubuntu1.1                                    all          MySQL database common files, e.g. /etc/mysql/my.cnf  
iU  mysql-server                                         5.7.12-0ubuntu1.1                                    all          MySQL database server (metapackage depending on the latest version)  
rc  mysql-server-5.5                                     5.5.43-0ubuntu0.14.10.1                              amd64        MySQL database server binaries and system database setup  
rc  mysql-server-5.6                                     5.6.16-1~exp1                                        amd64        MySQL database server binaries and system database setup  
iF  mysql-server-5.7                                     5.7.12-0ubuntu1.1                                    amd64        MySQL database server binaries and system database setup  
ii  mysql-server-core-5.7                                5.7.12-0ubuntu1.1                                    amd64        MySQL database server binaries  
ii  php-mysql                                            1:7.0+42+deb.sury.org~xenial+2                       all          MySQL module for PHP [default]  
ii  php5.6-mysql                                         5.6.23-1+deb.sury.org~xenial+2                       amd64        MySQL module for PHP  
ii  php7.0-mysql                                         7.0.8-2+deb.sury.org~xenial+1                        amd64        MySQL module for PHP  

Best Answer

First make a mysqldump of all your databases (including information_schema). Then "stop" mysql" and this will remove anything related to mysql:

sudo apt-get purge mysql-server mysql-client mysql-common mysql-server-core-5.7 mysql-client-core-5.7

# Backup 5.6 config and data without deleting
sudo mv /etc/mysql /etc/mysql-5.6-backup
sudo mv /var/lib/mysql /var/lib/mysql-5.6-backup
sudo apt-get autoremove
sudo apt-get autoclean

and then

sudo apt-get install mysql-client-5.6
sudo apt-get update

Warnings:

  • Ubuntu switched to systemd with 16.04. You may need to start 16.04 with upstart too when using mysql 5.6.