mysql service fails to start/hangs up - timeout (Ubuntu, MariaDB)

Question

I set up my first Ubuntu Server with Ubuntu 16.04, nginx, php7.0, MariaDB, nextcloud and external DynDNS using this tutorial here: Install Nextcloud 9 on Ubuntu 16.04

Answer 1

FYI:

In my case neither the solution of Vincent or Lw Bi worked exactly, I needed some further actions.

Disabling the profile through placing a link in /etc/apparmor.d/disable/ simply didn't work, I don't know why.

On the other hand, setting MySQL to complain mode didn't work either immediately.

:~$ sudo aa-complain /usr/sbin/mysqld

Setting /usr/sbin/mysqld to complain mode.

ERROR: /etc/apparmor.d/usr.sbin.mysqld contains no profile

I needed to add the lines:

/usr/sbin/mysqld {
}

to /etc/apparmor.d/usr.sbin.mysqld, and then I could set it to complain mode successfully.

Answer 2

This last option worked for me (from quazgar). I have Ubuntu 18.10 installed with MariaDB 10.3.13:

$ echo "/usr/sbin/mysqld { }" > /etc/apparmor.d/usr.sbin.mysqld
$ apparmor_parser -v -R /etc/apparmor.d/usr.sbin.mysqld
$ systemctl restart mariadb

I had to use "sudo su" for it to work though.

Answer 3

Run the following commands:

sudo dpkg --configure -a
sudo service mysql start

Answer 4

In case you are bitten by this bug, the solution is given as a suggestion in the bug report:

1. echo "/usr/sbin/mysqld { }" > /etc/apparmor.d/usr.sbin.mysqld
2. apparmor_parser -v -R /etc/apparmor.d/usr.sbin.mysqld
3. systemctl restart mariadb

Background

If you previously had MySQL installed, it activated an AppArmor profile which is incompatible with MariaDB. apt-get remove --purge only removes the profile, but does not deactivate/unload it. Only manually unloading it lets MariaDB work unhindered by AppArmor.