title: MySQL 5.7 Upgrade error on Ubuntu 16.04
body: <p>I was just uninstalling nginx and then in that apt-get remove command, I see that mysql-server is updating. Then the update hung up. I killed the "apt-get" process (followed some answer somewhere). Then things kept on happening and the mysql was completely screwed up. I followed @jargonjunkie 's answer here: <a href="https://askubuntu.com/questions/763534/cannot-reinstall-mysql-server-after-its-purge">https://askubuntu.com/questions/763534/cannot-reinstall-mysql-server-after-its-purge</a> also but to no avail.
  (I have even removed /var/lib/mysql and /etc/mysql).</p>
  
  <p>Here's what happens when I try to start mysql:</p>
  
  <pre><code>root@lamp-512mb-nyc1-01:~/etc/mysql# sudo /etc/init.d/mysql start
  [....] Starting mysql (via systemctl): mysql.serviceJob for mysql.service failed because the control process exited with error code. See "systemctl status mysql.service" and "journalctl -xe" for details.
  failed!
  </code></pre>
  
  <p>Here's what "systemctl status mysql.service" shows:</p>
  
  <pre><code>root@lamp-512mb-nyc1-01:~/etc/mysql# systemctl status mysql.service
  ● mysql.service - MySQL Community Server
  Loaded: loaded (/lib/systemd/system/mysql.service; enabled; vendor preset: enabled)
  Active: activating (start-post) (Result: exit-code) since Tue 2017-10-24 13:40:38 UTC; 13s ago
  Process: 21324 ExecStart=/usr/sbin/mysqld (code=exited, status=1/FAILURE)
  Process: 21315 ExecStartPre=/usr/share/mysql/mysql-systemd-start pre (code=exited, status=0/SUCCESS)
  Main PID: 21324 (code=exited, status=1/FAILURE);         : 21325 (mysql-systemd-s)
  Tasks: 2
  Memory: 18.2M
    CPU: 423ms
  CGroup: /system.slice/mysql.service
         └─control
           ├─21325 /bin/bash /usr/share/mysql/mysql-systemd-start post
           └─21357 sleep 1
  
  Oct 24 13:40:38 lamp-512mb-nyc1-01 systemd[1]: Starting MySQL Community Server...
  Oct 24 13:40:38 lamp-512mb-nyc1-01 systemd[1]: mysql.service: Main process exited, code=exited, status=1/FAILURE
  </code></pre>
  
  <p>I have seen several questions related to mysql-server 5.7 upgrade on ubuntu, but couldn't find anything that worked. 
  Please help. Thanks in advance.</p>