Linux – ulimit -n not changing – values limits.conf has no effect

bashlinuxpamUbuntuulimit

I am trying to raise the open file descriptor maximum for all users on an ubuntu machine.

This question is somewhat of a follow up to this question.

open file descriptor limits.conf setting isn't read by ulimit even when pam_limits.so is required

except that i've added the required "root" entries in limits.conf

Here are the entries

*               soft    nofile           100000
*               hard    nofile           100000
root            soft    nofile           100000
root            hard    nofile           100000

Lines related to pam_limits.so have been un-commented in all relevant files in /etc/pam.d/ and fs.file-max has been set correctly in /etc/sysctl.conf

However, I still see

abc@machine-2:/etc/pam.d$ ulimit -n
1024

after reboot.

What could be the problem?

My default shell is /bin/sh and i can't use chsh to change my default shell since the my user on the machine is authenticated via some distributed authentication scheme.

Best Answer

I had a similar problem, but with SSH logins only. Local logins (via console) respected the /etc/security/limits.conf.

As it turned out, when you set:

UsePrivilegeSeparation yes

in /etc/ssh/sshd_config file, then sshd forks an unprivileged child to set up the account's env. Because this child is unprivileged, then pam_limits.so setting upper limits had no effect.

As soon as I set

UsePrivilegeSeparation no

in /etc/ssh/sshd_config and bounced the SSH service, then the limits.conf file were respected with SSH logins.

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