How to set nginx max open files?

Question

On CentOS (tested on 7.x):

Create file /etc/systemd/system/nginx.service.d/override.conf with the following contents:

[Service]
LimitNOFILE=65536

Reload systemd daemon with:

systemctl daemon-reload

Add this to Nginx config file:

worker_rlimit_nofile 16384; (has to be smaller or equal to LimitNOFILE set above)

And finally restart Nginx:

systemctl restart nginx

You can verify that it works with cat /proc/<nginx-pid>/limits.