MySQL failed to restart on Ubuntu 16.04

Fatal Error:

MYQL is failing to start because as the Journalctl output indicates, but you haven't provided the mandatory server-id. Add the mandatory id as indicated in the code below.

/etc/mysql/mysql.conf.d/mysqld.cnf
Change from:

log-bin=mysql-bin
binlog-format = 'ROW'

Change to:

server-id=master-01
log-bin=mysql-bin
binlog-format = 'ROW'

This will get your server running while you address the proper formatting of your desired logging.

non-fatal warnings:

For the open files limit of your error you will have to either decrease the demand in the configuration you edited or increase the system's limits with:

/etc/security/limits.conf

* soft nofile [new number]
* hard nofile [new number]

The first column describes WHO the limit is to apply for. '' is a wildcard, meaning all users. To raise the limits for root, you have to explicitly enter 'root' instead of ''.

Taken from:
https://askubuntu.com/a/162230/29012

Got the same error, but in my case simply the disk was full. Make also sure to check this.

df -h --total