How to Increase max_connections of MySQL service on Ubuntu 16.04

From: http://stackoverflow.com/questions/30901041/can-not-increase-max-open-files-for-mysql-max-connections-in-ubuntu-15, by Fredik

As of MySQL 5.7.7, this is what the documentation recommends for Red Hat Enterprise Linux 7, Oracle Linux 7, CentOS 7, SUSE Linux Enterprise Server 12, Fedora 24 and 25:

https://dev.mysql.com/doc/refman/5.7/en/using-systemd.html

On Ubuntu 16.04 the service is called mysql, not mysqld, so this is what Fredik did:

sudo mkdir /etc/systemd/system/mysql.service.d
sudo vi /etc/systemd/system/mysql.service.d/override.conf

Added this in the new file override.conf:

[Service]
LimitNOFILE=5000

Then restarted the service:

sudo systemctl daemon-reload
sudo systemctl restart mysql