:/# apt install mysql-server-5.7
Reading package lists... Done
Building dependency tree
Reading state information... Done
Suggested packages:
  mailx tinyca
The following NEW packages will be installed:
  mysql-server-5.7
0 upgraded, 1 newly installed, 0 to remove and 5 not upgraded.
Need to get 0 B/3,363 kB of archives.
After this operation, 50.0 MB of additional disk space will be used.
Preconfiguring packages ...
Selecting previously unselected package mysql-server-5.7.
(Reading database ... 98007 files and directories currently installed.)
Preparing to unpack .../mysql-server-5.7_5.7.19-0ubuntu0.17.04.1_amd64.deb ...
Unpacking mysql-server-5.7 (5.7.19-0ubuntu0.17.04.1) ...
Processing triggers for ureadahead (0.100.0-19) ...
Processing triggers for systemd (232-21ubuntu5) ...
Processing triggers for man-db (2.7.6.1-2) ...
Setting up mysql-server-5.7 (5.7.19-0ubuntu0.17.04.1) ...
update-alternatives: using /etc/mysql/mysql.cnf to provide /etc/mysql/my.cnf (my.cnf) in auto mode
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 16:58:25 EDT; 15ms ago
  Process: 29965 ExecStartPost=/usr/share/mysql/mysql-systemd-start post (code=exited, status=0/SUCCESS)
  Process: 29964 ExecStart=/usr/sbin/mysqld (code=exited, status=1/FAILURE)
  Process: 29956 ExecStartPre=/usr/share/mysql/mysql-systemd-start pre (code=exited, status=0/SUCCESS)
 Main PID: 29964 (code=exited, status=1/FAILURE)
      CPU: 304ms

Sep 08 16:58:25 LKNServer-Ubuntu systemd[1]: Failed to start MySQL Community Server.
Sep 08 16:58:25 LKNServer-Ubuntu systemd[1]: mysql.service: Unit entered failed state.
Sep 08 16:58:25 LKNServer-Ubuntu systemd[1]: mysql.service: Failed with result 'exit-code'.
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)