>>> I've edited the /etc/security/limits.conf and added
>>> * soft stack 12288
>>> * hard stack 12288
>> on a CentOS 6.7 box I can confirm that adding those lines to
>> /etc/security/limits.conf DOES increase the limit to 12288
>> (after a reboot).
>>
>> I don't see the PAM line, though. What version of CentOS are
>> you using?
> I'm using CentOS7.1, here's the heading from my /etc/security/limit.conf
> [...]
> #It does not affect resource limits of the system services.
> well what does!??
I don't have yet a lot of experience with Centos7, but so far
whenever things that used to work in Centos6 didn't in Centos7
for me the guilty part was systemd. Systemd is the new replacement
for init and a bunch of other things.
If I google
systemd security/limits.conf
I get hits that your problem too is due to systemd.
For example here is a guide to change one of the ulimits in centos7:
https://ma.ttias.be/increase-open-files-limit-in-mariadb-on-centos-7-with-systemd/
I don't know if that works, but it is in line with the
"systemd broke things" idea...
Bye,
Chris.