How can I increase open files limit for all processes?

Question

I can use ulimit but I think that only affects my shell session. I want the limit increased for all processes. This is on Red Hat.

Answer 1

Justin's answer tells you how to raise the number of open files available total to the whole system. But I think you're asking how to raise the per-user limit, globally. The answer to that is to add the following lines to /etc/security/limits.conf:

*               soft    nofile            2048
*               hard    nofile            2048

(Where the * means all users.)

There's some summary documentation in that file itself and in man limits.conf. This is implemented via the pam_limits.so module which is called for various services configured in /etc/pam.d/.

And, I have to admit, I have no idea where that 1024 default comes from. And believe me, I looked. I even tried without the pam_limits module configured, and it's still there. It must be hard-coded in somewhere, but I'm not exactly sure where.

Answer 2

According to the article Linux Increase The Maximum Number Of Open Files / File Descriptors (FD), you can increase the open files limit by adding an entry to /etc/sysctl.conf.

Append a config directive as follows:

fs.file-max = 100000

Then save and close the file. Users need to log out and log back in again to changes take effect or they can just type the following command:

# sysctl -p

You can also verify your settings with the command:

# cat /proc/sys/fs/file-max