root@ali-Latitude-E6420:~# service mysql stop
root@ali-Latitude-E6420:~# killall -KILL mysql mysqld_safe mysqld
mysql: no process found
mysqld_safe: no process found
mysqld: no process found
root@ali-Latitude-E6420:~# apt-get --yes purge mysql-server mysql-client
Reading package lists... Done
Building dependency tree       
Reading state information... Done
Package 'mysql-client' is not installed, so not removed
The following packages were automatically installed and are no longer required:
  libaio1 mysql-client-5.7 mysql-client-core-5.7 mysql-common mysql-server-5.7
  mysql-server-core-5.7
Use 'sudo apt autoremove' to remove them.
The following packages will be REMOVED:
  mysql-server*
0 upgraded, 0 newly installed, 1 to remove and 0 not upgraded.
2 not fully installed or removed.
After this operation, 159 kB disk space will be freed.
(Reading database ... 413698 files and directories currently installed.)
Removing mysql-server (5.7.12-0ubuntu1) ...
Setting up mysql-server-5.7 (5.7.12-0ubuntu1) ...
AppArmor parser error for /etc/apparmor.d/usr.sbin.mysqld in /etc/apparmor.d/usr.sbin.mysqld at line 9: Could not open 'abstractions/mysql'
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
Errors were encountered while processing:
 mysql-server-5.7
E: Sub-process /usr/bin/dpkg returned an error code (1)
root@ali-Latitude-E6420:~# apt-get --yes autoremove --purge
Reading package lists... Done
Building dependency tree       
Reading state information... Done
The following packages will be REMOVED:
  libaio1* mysql-client-5.7* mysql-client-core-5.7* mysql-common*
  mysql-server-5.7* mysql-server-core-5.7*
0 upgraded, 0 newly installed, 6 to remove and 0 not upgraded.
1 not fully installed or removed.
After this operation, 160 MB disk space will be freed.
(Reading database ... 413694 files and directories currently installed.)
Removing mysql-server-5.7 (5.7.12-0ubuntu1) ...
update-alternatives: using /etc/mysql/my.cnf.fallback to provide /etc/mysql/my.cnf (my.cnf) in auto mode
Purging configuration files for mysql-server-5.7 (5.7.12-0ubuntu1) ...
Removing mysql-server-core-5.7 (5.7.12-0ubuntu1) ...
Removing mysql-client-5.7 (5.7.12-0ubuntu1) ...
Removing mysql-client-core-5.7 (5.7.12-0ubuntu1) ...
Removing libaio1:amd64 (0.3.110-2) ...
Removing mysql-common (5.7.12-0ubuntu1) ...
Purging configuration files for mysql-common (5.7.12-0ubuntu1) ...
dpkg: warning: while removing mysql-common, directory '/etc/mysql' not empty so not removed
Processing triggers for man-db (2.7.5-1) ...
Processing triggers for libc-bin (2.23-0ubuntu3) ...
root@ali-Latitude-E6420:~# apt-get autoclean
Reading package lists... Done
Building dependency tree       
Reading state information... Done
root@ali-Latitude-E6420:~# deluser --remove-home mysql
Looking for files to backup/remove ...
Removing user `mysql' ...
Warning: group `mysql' has no more members.
Done.
root@ali-Latitude-E6420:~# delgroup mysql
The group `mysql' does not exist.
root@ali-Latitude-E6420:~# rm -rf /etc/apparmor.d/abstractions/mysql /etc/apparmor.d/cache/usr.sbin.mysqld /etc/mysql /var/lib/mysql /var/log/mysql* /var/log/upstart/mysql.log* /var/run/mysqld
root@ali-Latitude-E6420:~# updatedb