Ubuntu – 16.04 upgrade broke thesql-server

16.04MySQLupgrade

My overall upgrade went well, but I am left with a critically lingering issue of mysql-server not being able to install itself, and nothing I am trying gets it to work.

This is the error I see when trying to install/reinstall it:

Setting up mysql-server-5.7 (5.7.11-0ubuntu6) ...
Job for mysql.service failed because the control process exited with error code. See "systemctl status mysql.service" and "journalctl -xe" for details.
invoke-rc.d: initscript mysql, action "start" failed.
dpkg: error processing package mysql-server-5.7 (--configure):
 subprocess installed post-installation script returned error exit status 1
dpkg: dependency problems prevent configuration of mysql-server:
 mysql-server depends on mysql-server-5.7; however:
  Package mysql-server-5.7 is not configured yet.

dpkg: error processing package mysql-server (--configure):
 dependency problems - leaving unconfigured
No apport report written because the error message indicates its a followup error from a previous failure.
                   Processing triggers for systemd (229-4ubuntu4) ...
Processing triggers for ureadahead (0.100.0-19) ...
Errors were encountered while processing:
 mysql-server-5.7
 mysql-server
E: Sub-process /usr/bin/dpkg returned an error code (1)

I've tried completely removing it, though doing so attempts to install MariaDB because of dependencies (?). Any suggestions on what I can do to fix this would be most welcome.

EDIT:
Looks like I'm not the only one: https://bugs.launchpad.net/ubuntu/+source/mysql-5.7/+bug/1573279

Best Answer

The instructions @andrew-beerman posted are on the right track, though they aren't quite clear to me and seem to recommend more than is necessary. I pieced together the answer from the above and a helpful post in the bug thread.

These are the steps I took to correct this:

Back up your my.cnf file in /etc/mysql and remove or rename it
```
sudo mv /etc/mysql/my.cnf /etc/mysql/my.cnf.bak
```
Remove the folder /etc/mysql/mysql.conf.d/ using
```
sudo rm -r /etc/mysql/mysql.conf.d/
```
Verify you don't have a my.cnf file stashed somewhere else (I did in my home dir!) or in /etc/alternatives/my.cnf use
```
sudo find / -name my.cnf
```

Backup and remove /etc/mysql/debian.cnf files (not sure if needed, but just in case)

sudo mv /etc/mysql/debian.cnf /etc/mysql/debian.cnf.bak
sudo apt purge mysql-server mysql-server-5.7 mysql-server-core-5.7
sudo apt install mysql-server

In case your syslog shows an error like "mysqld: Can't read dir of '/etc/mysql/conf.d/'" create a symbolic link:
```
sudo ln -s /etc/mysql/mysql.conf.d /etc/mysql/conf.d
```
Then the service should be able to start with sudo service mysql start.

That got it working!

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Shutting down apache2 first before installing nginx should fix this problem:

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Ubuntu – thesql doesn’t ask for root password when installing

You can recover or set root password without knowing the current one by starting mysql without loading the grant-tables.

Please note the $ in the commands. This is specifying the terminal prompt you see when typing in the command. It's showing it's a line of text, but and actual typed terminal command. The "mysql>" prefix is also a prompt. That is the prompt you get when running mysql interactivately.

This is the cli (command line) to do this:
(Be sure to stop the current server before performing the steps. Only one server can run at a time.)

$ sudo mkdir /var/run/mysqld; sudo chown mysql /var/run/mysqld
$ sudo mysqld_safe --skip-grant-tables&

Now you can log in as root without a password and perform all commands, as in this case, set the root password as root.

$ sudo mysql --user=root mysql

This is the set root password that you will perform inside mysql if you have MySQL 5.6 or below:

mysql> update user set Password=PASSWORD('new-password') where user='root';
flush privileges;

In MySQL 5.7 or above

mysql> update user set authentication_string=PASSWORD('new-password') where user='root';
flush privileges;

From there, quit (kill the running msqld) mysql and start it as normal.

Notes on starting and stopping the mysql service:

Stop mysql:

$ sudo service mysql stop

Start mysql (normal):

$ sudo service mysql start

Kill the temporary mysql safe mode session:

$ sudo mysqladmin shutdown

Best Answer

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