Set max file limit on a running process

As documented here, the prlimit command, introduced with util-linux 2.21 allows you to read and change the limits of running processes.

This is a followup to the writable /proc/<pid>/limits, which was not integrated in mainline kernel. This solution should work.

If you don't have prlimit(1) yet, you can find the code to a minimalistic version in the prlimit(2) manpage.

On newer kernels (2.6.32+) on CentOS/RHEL you can change this at runtime with /proc/<pid>/limits:

cd /proc/7671/
[root@host 7671]# cat limits  | grep nice
Max nice priority         0                    0                    
[root@host 7671]# echo -n "Max nice priority=5:6" > limits
[root@host 7671]# cat limits  | grep nice
Max nice priority         5                    6                    

On newer version of util-linux-ng you can use prlimit command, for more infomation read this link https://superuser.com/questions/404239/setting-ulimit-on-a-running-process

You can try ulimit man ulimit with the -n option however the mag page does not most OS's do not allow this to be set.

You can set a system wide file descriptions limit using sysctl -w fs.file-max=N and make the changes persist post boot up in /etc/sysctl.conf

However I would also suggest looking at the process to see if it really needs to have so many files open at a given time, and if you can in fact close some files down and be more efficient in the process.