- Show no of open files sorted by PID -
lsof | awk '{ print $2; }' | uniq -c | sort -rn | head - Check individual file limits of a process -
cat /proc/<PID>/limits - to obtain a precise count of the open files at given instant of time -
ls /proc/<PID>/fd | wc -l - This will list all open files with given process -
lsof -p <PID>
In some cases you might have to look at the open file limit of the process which started your process.
Make sure you add ulimit -n XXX values inside your startup script, if you have configured it to start the process on machine startup or restart. Especially on Debian Linux flavour refer (https://bugs.launchpad.net/ubuntu/+source/upstart/+bug/938669)