topic ulimt question in Operating System - Linux

ulimt question

joseph wholey — Wed, 13 Sep 2006 10:00:22 GMT

RHEL 4. I'm trying to set the ulimit for open files (ulimit -n) on one of my RHEL servers from the default to 66536. I put the value in my /etc/sysctl.conf as follows:
fs.file-max = 65536.

However, when I log in as root or any other user, it is set to the default value of 1024. Why is that?

Re: ulimt question

Alexander Chuzhoy — Wed, 13 Sep 2006 10:22:58 GMT

ulimit is to be set in files that control your shell. For example for all users on the system that use bash edit /etc/bashrc.
ulimit -n number
In /etc/sysctl.conf file your define kernel tunnings.

Re: ulimt question

sandeep_raman — Wed, 13 Sep 2006 10:23:55 GMT

Hello joseph,

http://forums1.itrc.hp.com/service/forums/questionanswer.do?threadId=69798
http://www.linuxquestions.org/questions/showthread.php?postid=592509

Hope this helps.

SRH

Re: ulimt question

George Liu_4 — Wed, 13 Sep 2006 10:57:43 GMT

There should no trailing dot (.) after 65536.
BTW, default file-max is 102043 on RHEL4. Can you get the output of

cat /proc/sys/fs/file-max

Re: ulimt question

joseph wholey — Wed, 13 Sep 2006 11:14:56 GMT

Thanks for all of the responses... one remaining question... why when I issue "ulimit -n" I get 1024, but when I look in /proc/sys/fs/file-max, it's set to what I have in /etc/sysctl.conf. What is ulimit -n showing me, and where is it picking up the value?

Re: ulimt question

Jorge Cocomess — Wed, 13 Sep 2006 12:36:44 GMT

Joseph,

Just a quick clarification, Max-File and Ulimit are two different parameters.

Max-file:
file-max is a system level maximum number of file handles that the system will allocate. The cumulative number across all jobs cannot exceed that.

Ulimit:
ulimit sets the limit for the process itself. So for a telnet session, ulimit can be used to set the soft limit up or down for a particular resource for that telnet session and its child processes. (And ulimit can set the hard limit down, but not up).

The only paramter that you should worry about is the limits.conf and add the user that you'd like to have the ulimit increased (/etc/security/limits.conf).
Once you done that, restart the sshd service. Have the user log back in and do this command ulimit -a

Let me know if you need more details on this.

Jorge

Re: ulimt question

joseph wholey — Wed, 13 Sep 2006 13:32:02 GMT

Jorge,

I did exactly as you specified... updated the /etc/security/limits.conf as follows:

usr hard nofile 65536

recycled the sshd daemon, logged out, logged back in as 'usr', issued ulimit -a, and open files still has the value of 1024.

Re: ulimt question

Jorge Cocomess — Fri, 15 Sep 2006 08:31:18 GMT

How much memory do you have on your box?

What's your setting for max-file?
What's your limits.conf file look like now?

Please give me these details and I will try to help you.

Jorge

Re: ulimt question

Mike Stroyan — Wed, 20 Sep 2006 13:40:47 GMT

The limits setting in /etc/security/limits.conf is done by a PAM login. You need to have a "UsePAM yes" line in /etc/ssh/sshd_config in order to tell sshd to use PAM. Without that the limits.conf setting will be ignored for ssh logins.
You should look through "man sshd_config" to see that you are getting the behavior you want from sshd and PAM after making this change.