check current limitation:

#ulimit -n

increase limitation:

#vi /etc/security/limits.conf

Add the following values in file:

* 	 soft     nproc          65535
* 	 hard     nproc          65535
* 	 soft     nofile         65535
* 	 hard     nofile         65535
root 	 soft     nproc          200000
root 	 hard     nproc          200000
root 	 soft     nofile         200000
root 	 hard     nofile         200000
#vi /etc/sysctl.conf 

Add the following line:

fs.file-max = 2097152


#sysctl -p

check new limitations:

#ulimit  -n

Note For Docker:

if you want to execute ulimit inside unprivileged docker container you will get:

ulimit: open files: cannot modify limit: Operation not permitted

For resolving this execute below commands on docker HOST:

ulimit -l unlimited
ulimit -n 2097152 
ulimit -c unlimited

Then Restart Docker Service. The Problem Solved

Note: Increase Open Files Limit Per Process

current limit:

cat /proc/<pid>/limits | grep files

change limit:

prlimit -n65535 -p pid_of_process

By: Mehdi Sadighian
TAG: ubuntu, too many open files, increase file descriptor limitation, increase open files limit