Preparing to unpack .../libaio1_0.3.110-2_amd64.deb ...
Unpacking libaio1:amd64 (0.3.110-2) ...
Selecting previously unselected package mysql-client-core-5.7.
Preparing to unpack .../mysql-client-core-5.7_5.7.21-0ubuntu0.16.04.1_amd64.deb ...
Unpacking mysql-client-core-5.7 (5.7.21-0ubuntu0.16.04.1) ...
Selecting previously unselected package mysql-client-5.7.
Preparing to unpack .../mysql-client-5.7_5.7.21-0ubuntu0.16.04.1_amd64.deb ...
Unpacking mysql-client-5.7 (5.7.21-0ubuntu0.16.04.1) ...
Selecting previously unselected package mysql-server-core-5.7.
Preparing to unpack .../mysql-server-core-5.7_5.7.21-0ubuntu0.16.04.1_amd64.deb ...
Unpacking mysql-server-core-5.7 (5.7.21-0ubuntu0.16.04.1) ...
Selecting previously unselected package libevent-core-2.0-5:amd64.
Preparing to unpack .../libevent-core-2.0-5_2.0.21-stable-2ubuntu0.16.04.1_amd64.deb ...
Unpacking libevent-core-2.0-5:amd64 (2.0.21-stable-2ubuntu0.16.04.1) ...
Selecting previously unselected package mysql-server-5.7.
Preparing to unpack .../mysql-server-5.7_5.7.21-0ubuntu0.16.04.1_amd64.deb ...
Unpacking mysql-server-5.7 (5.7.21-0ubuntu0.16.04.1) ...
Selecting previously unselected package mysql-server.
Preparing to unpack .../mysql-server_5.7.21-0ubuntu0.16.04.1_all.deb ...
Unpacking mysql-server (5.7.21-0ubuntu0.16.04.1) ...
Processing triggers for libc-bin (2.23-0ubuntu10) ...
Processing triggers for man-db (2.7.5-1) ...
Processing triggers for systemd (229-4ubuntu21.1) ...
Processing triggers for ureadahead (0.100.0-19) ...
Setting up libaio1:amd64 (0.3.110-2) ...
Setting up mysql-client-core-5.7 (5.7.21-0ubuntu0.16.04.1) ...
Setting up mysql-client-5.7 (5.7.21-0ubuntu0.16.04.1) ...
Setting up mysql-server-core-5.7 (5.7.21-0ubuntu0.16.04.1) ...
Setting up libevent-core-2.0-5:amd64 (2.0.21-stable-2ubuntu0.16.04.1) ...
Setting up mysql-server-5.7 (5.7.21-0ubuntu0.16.04.1) ...
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 Sun 2018-03-11 21:24:32 IST; 9ms ago
  Process: 6963 ExecStartPre=/usr/share/mysql/mysql-systemd-start pre (code=exited, status=1/FAILURE)

Mar 11 21:24:32 akshay-VirtualBox systemd[1]: mysql.service: Control process...1
Mar 11 21:24:32 akshay-VirtualBox systemd[1]: Failed to start MySQL Communit....
Mar 11 21:24:32 akshay-VirtualBox systemd[1]: mysql.service: Unit entered fa....
Mar 11 21:24:32 akshay-VirtualBox systemd[1]: mysql.service: Failed with res....
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