ulimit error while changing max files to unlimited: PAM / sshd options?

[Mike Burger]

> I tried changing the max limit on the number of open files but get an
> error:
>
> ssh root at eu033
> [root at eu033 ~]# ulimit -n unlimited
> -bash: ulimit: open files: cannot modify limit: Operation not permitted
>
> I verified that /etc/security/limits.conf has these two lines:
> *               hard    nofile          unlimited
> *               soft    nofile          unlimited
>
> The default kernel limits seem high enough:
> [root at eu033 ~]# cat /proc/sys/fs/file-max
> 1585781
>
> [root at eu033 ~]# sysctl -a|grep fs.file-max
> fs.file-max = 1585781
>
> So why is my change via ulimit being rejected? What else could be
> setting the limit at 1024. Any ideas how else I can get the file-limit
> to be set to unlimited?

I don't believe that you can dynamically set a ulimit value that is higher
than the value currently in use...

> Actually, I am not even sure limits.conf is being used since I have
> the following lines in the file /etc/ssh/sshd_config
>
> UsePAM no
> UsePrivilegeSeparation no

PAM and ulimits are mutually exclusive...one does not affect the other. 
In my experience, if you want to use unlimited ulimit settings, you need
to set them in the limits.conf file, and then start a new shell.

You can also set lower limits on a user by user basis by adding ulimit
commands to their .bash_profile files.

-- 
Mike Burger
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