If you are setting up nginx,chances are you will discover your worker_connections is at some low number, such as 1024.
You can’t increase this number unless you increase kernel limit as well.
First of all run cat /proc/sys/fs/file-max to discover your maximum limit.

abc@ubuntu:~$ cat /proc/sys/fs/file-max
1048576
abc@ubuntu:~$ ulimit -n
1024

As you can see there’s plenty of space for improvement. Lets say I want my new ‘ulimit -n’ to read 131072.

abc@ubuntu:~$ sudo nano /etc/sysctl.conf

add

fs.file-max = 131072

run

sudo sysctl -p

edit

sudo nano /etc/security/limits.conf

add

* soft     nproc          131072    
* hard     nproc          131072   
* soft     nofile         131072   
* hard     nofile         131072
root soft     nproc          131072    
root hard     nproc          131072   
root soft     nofile         131072   
root hard     nofile         131072

sudo nano /etc/pam.d/common-session

add

session required pam_limits.so

And that’s it. Log out and in and try ulimit -n

abc@ubuntu:~$ ulimit -n 131072

Now you can edit nginx as well

events {
    worker_connections 131072;
    use epoll;
    multi_accept on;
}