ulimit - Runtime system resource tuning

When you're dealing with daemons, you're likely to run into the system's process-level constraints. In additional to the kernel params that are set in the setup scripts, there are process limits you need to be aware of to keep from bumping your head.

The shell has a built-in command to query and set those values: ulimit.

ulimit: usage: ulimit [-SHacdfilmnpqstuvx] [limit]

brutus:~ nsmc$ ulimit -a

core file size (blocks, -c) 0

data seg size (kbytes, -d) unlimited

file size (blocks, -f) unlimited

max locked memory (kbytes, -l) unlimited

max memory size (kbytes, -m) unlimited

open files (-n) 256

pipe size (512 bytes, -p) 1

stack size (kbytes, -s) 8192

cpu time (seconds, -t) unlimited

max user processes (-u) 266

virtual memory (kbytes, -v) unlimited

As you can see, there are very tight limits on this system for the number of processes a user can run, as well as the number of files any of those processes can have open.

These values can be set using a basic syntax:

#ulimit -n 9162

However, they won't survive a reboot. Since these limits are tied to the shell process that invokes them, you need to set them in /etc/bashrc (or whatever your shell takes its initialization parameters from) in order to have them come up automatically.