# apt purge mysql-server
Reading package lists... Done
Building dependency tree       
Reading state information... Done
The following packages were automatically installed and are no longer required:
  mysql-client-5.7 mysql-common mysql-server-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 5 not upgraded.
2 not fully installed or removed.
After this operation, 177 kB disk space will be freed.
Do you want to continue? [Y/n] Y
(Reading database ... 98077 files and directories currently installed.)
Removing mysql-server (5.7.19-0ubuntu0.17.04.1) ...
Setting up mysql-server-5.7 (5.7.19-0ubuntu0.17.04.1) ...
Renaming removed key_buffer and myisam-recover options (if present)
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.
● mysql.service - MySQL Community Server
   Loaded: loaded (/lib/systemd/system/mysql.service; enabled; vendor preset: enabled)
   Active: activating (auto-restart) (Result: exit-code) since Fri 2017-09-08 16:35:54 EDT; 13ms ago
  Process: 26774 ExecStartPost=/usr/share/mysql/mysql-systemd-start post (code=exited, status=0/SUCCESS)
  Process: 26773 ExecStart=/usr/sbin/mysqld (code=exited, status=1/FAILURE)
  Process: 26765 ExecStartPre=/usr/share/mysql/mysql-systemd-start pre (code=exited, status=0/SUCCESS)
 Main PID: 26773 (code=exited, status=1/FAILURE)
      CPU: 296ms

Sep 08 16:35:54 LKNServer-Ubuntu systemd[1]: Failed to start MySQL Community…er.
Sep 08 16:35:54 LKNServer-Ubuntu systemd[1]: mysql.service: Unit entered fai…te.
Sep 08 16:35:54 LKNServer-Ubuntu systemd[1]: mysql.service: Failed with resu…e'.
Hint: Some lines were ellipsized, use -l to show in full.
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)