How can I downgrade mysql 5.7 to 5.6 on Ubuntu 16.04?

Question

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

The official Ubuntu 16.04 repositories only have 5.7, so first you will need to find a repository which provides 5.6. Maybe the official MySQL one. — fkraiem, Jun 29 '16 at 03:21
You shouldn't do that, especially since it seems there are 5.6 packages for Xenial. — fkraiem, Jun 29 '16 at 03:38
For example, the system to manage services has changed (Trusty uses upstart, Xenial uses systemd), so it is not surprising that a service in a package made for Trusty (with upstart) does not start in Xenial (with systemd). — fkraiem, Jun 29 '16 at 03:40
Ah wow. Maybe this is why no matter what I have tried seems to work. — dibs, Jun 29 '16 at 03:41
Oh also, please include the output of dpkg -l | grep mysql so we can see the MySQL packages you have installed and their version numbers. — fkraiem, Jun 29 '16 at 03:42

score 7 · Answer 1 · edited May 24 '18 at 22:42

7

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.

edited May 24 '18 at 22:42

fosslinux

3,831

answered Jun 29 '16 at 03:33

Tyler

89

1

I'm pretty sure that $ sudo rm -rf on /var/lib/mysql will blow away all of my databases. – dibs Jun 29 '16 at 03:39
It will but you can not keep /var/lib/mysql/ anyways. You need a dump of your database so you can reload it. Otherwise you'd pick up settings from 5.7 than are invalid in 5.6 – Rinzwind Jun 29 '16 at 06:40
1

I see another mistake: mysql needs to be stopped before you remove it. And another warning: we switched to systemd between 5.6 and 5.7. Not a dealbreaker but worth mentioning – Rinzwind Jun 29 '16 at 06:42
@Rinzwind what does this practically mean re: the systemd change? Also good to know I HAVE to dump dbs. I'll make sure I do that first. – dibs Jun 30 '16 at 02:26
upstart was Ubuntu's own start up system for system and services. systemd is the same but more widely accepted so we switched to it. Means software for release 16.04 will provide systemd services and maybe an upstart and 15.10 and lower will provide upstart services. And the 2 do not mix. – Rinzwind Jun 30 '16 at 06:50
3

mysql-client-5.6 is no longer available in apt-get by default. See http://askubuntu.com/questions/762384/install-mysql-5-6-on-ubuntu-16-04 for how to install it. – Tony Sep 28 '16 at 20:07
Can't purge mysql 5.7 because of unmet dependencies, and can't install 5.6 anyway. Will look up @Tony link. – Shautieh Oct 28 '16 at 10:36
Package mysql-client-5.6 is not available, but is referred to by another package. – Kiran Reddy Jan 15 '18 at 06:19

score 0 · Answer 2 · edited May 24 '18 at 22:42

0

I added the Ubuntu 14.04 repository (in Ubuntu 18.04):

sudo add-apt-repository 'deb http://archive.ubuntu.com/ubuntu trusty universe'

I am able to install:

sudo apt install mysql-client-5.6

edited May 24 '18 at 22:42

fosslinux

3,831

answered May 24 '18 at 07:01

Rahul Thakur

11

2

This is a really bad idea. See https://askubuntu.com/questions/499800/can-i-mix-sources-from-different-ubuntu-versions. – fosslinux May 24 '18 at 22:40
Ok to do this, but don't update, and follow with "-r" remove once installe d"sudo add-apt-repository -r 'deb http://archive.ubuntu.com/ubuntu trusty universe'"as much as it is a bad idea to leave this in your repo, if you remove it once 5.6 is installed, I don't think this is as bad an idea as the above comment made. The same answer here has 60 upvotes, and he did an apt-get update, which has more potential to cause problems https://askubuntu.com/questions/762384/install-mysql-5-6-on-ubuntu-16-04#765458 – MagicLAMP Sep 13 '18 at 02:42

How can I downgrade mysql 5.7 to 5.6 on Ubuntu 16.04?

2 Answers2

Linked