[EN] Setting open descriptors on Ubuntu18.04

Hello! this is a tricky question; many times you are used to do something in an special way but suddenly, one day it doesn't work. That's what happened to me with open file descriptors on Ubuntu 18.04.

 By default this Ubuntu release has

esther@host:~# sudo ulimit -n
1024
esther@host:~#

which may be very little if you plan to run, for example, an nginx server. If you want to change that value, you have to

1) edit /etc/sysctl.conf and add

fs.file-max = 65535
fs.nr_open = 65535

at the end of the file

2) edit /etc/security/limits.conf and add at the end

* soft     nproc          65535   
* hard     nproc          65535  
* soft     nofile         65535  
* hard     nofile         65535
root soft     nproc          65535   
root hard     nproc          65535  
root soft     nofile         65535  
root hard     nofile         65535

3) check that 

/etc/pam.d/common-session 
/etc/pam.d/common-session-noninteractive 

contain

session    required    pam_unix.so

which is the default configuration for the pam.d service; if you need to update any of those two files, restart the pam.d service.

If you have done all of those changes, reload them and check if still have the same values

esther@host:~# sudo sysctl -p
esther@host:~# sudo ulimit -n

shows the default value, make one last change on /etc/systemd/user.conf and set

DefaultLimitNOFILE=65535

Save and restart... and check it again ;)