Server Fault is a question and answer site for system and network administrators. Join them; it only takes a minute:

Sign up
Here's how it works:
  1. Anybody can ask a question
  2. Anybody can answer
  3. The best answers are voted up and rise to the top

I have a problem where mysqld runs out of threads and throws errors when under heavy load. I have traced this back to a problem where the pid seems to be limited a soft limit of 1024 processes (have removed other limits for readability):

[root@db1 limits.d]# cat /proc/`pidof mysqld`/limits
Limit                     Soft Limit           Hard Limit           Units
Max processes             1024                 191967               processes

I have a file in /etc/security/limits.d/ called 99-mysql.conf which contains:

mysql soft nofile 20000
mysql hard nofile 20000
mysql soft nproc 20000
mysql hard nproc 20000

As far as I can see the problem comes from MySQL being started by a user. I haven't tested this, but I assume that if MySQL is started by the system at boot time, then it should have the correct limits.

Is there a way to increase the soft limit for nproc for this pid and for future mysqld processes?

share|improve this question

migrated from Dec 2 '13 at 0:57

This question came from our site for computer enthusiasts and power users.

It seems you can set the limits of a running pid by using:

echo -n "Max processes=20000:191967" > /proc/`pidof mysqld`/limits

This solves the immediate problem, but if I restart MySQL again I would need to reset the limits (unless I add this to the startup script), which seems like a pain.

share|improve this answer
I this can be done, only on new kernel version, because i saw this file on Redhat 5 is readonly /proc/$$/limits, on redhat 6 you can use prlimit or your trick – c4f4t0r Dec 24 '13 at 8:55

Look for and remove any entries in:


Also, add in your limits.d file:

root soft nofile 20000
root hard nofile 20000
root soft nproc 20000
root hard nproc 20000

That will cover restarts from the root prompt.

share|improve this answer
That might work fine, until the pam rpm package is updated next. – Noodles Dec 2 '13 at 3:02
True, edited my answer. – dmourati Dec 2 '13 at 3:07
Interestingly, I removed the * soft nproc 1024 line from /etc/security/limits.d/90-nproc.conf, logged out, logged back in and restarted mysql. This didn't increase the process limits for mysql. It may require a reboot. – Noodles Dec 2 '13 at 3:30
You may need to stop then start mysql, in case a restart re-uses the same process [?] – rogerdpack Sep 12 '14 at 17:07

Your Answer


By posting your answer, you agree to the privacy policy and terms of service.

Not the answer you're looking for? Browse other questions tagged or ask your own question.