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Old 06-16-2013, 10:16 PM   #1
Registered: Jan 2006
Distribution: Slackware
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How to set open file descriptor hard and soft limits

I have a script in /etc/profile.d that sets my normal unprivileged user account open file descriptors soft limit to 6144. I set it up years ago, but I just noticed that it isn't working anymore. I am not sure when it quit working, but it might have been when I upgraded from 32-bit Slackware 13.37 to 64-bit 14.0 about a month ago.

The /etc/profile.d/ script executes "ulimit -Sn 6144". I now get this message when I login:

-bash: ulimit: open files: cannot modify limit: Invalid argument
Of course I get the same error if I issue the ulimit command directly and specify a soft limit that exceeds the current hard limit of 4096. Apparently the hard limit used to be higher than 4096.

I don't know if the default hard limit changed in 14.0, or if I had increased the hard limit in the past and managed to lose that customization when I did the full install of 64-bit 14.0.

Here are limits as they exist on my system now:

$ cat /proc/sys/fs/file-max

$ ulimit -Sn

$ ulimit -Hn
I did some searches and found that system-wide limits can be set in /etc/sysctl.conf. I don't have that file, and I never have as far as I know. I also read that per-user/group/process limits can be set in /etc/security/limits.conf, but again, I have never had that file, or even the security subdirectory under /etc.

Where is the default open file descriptor hard limit set in Slackware? Did the default value change between 13.37 and 14.0?
Old 06-16-2013, 10:45 PM   #2
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Did you increase the hard limit before increasing the soft limit?
Old 06-16-2013, 11:01 PM   #3
Registered: Jan 2006
Distribution: Slackware
Posts: 841

Original Poster
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You mean like "ulimit -Hn 10000" or similar? No, that operation isn't permitted for unprivileged users. Unprivileged users can only alter the soft limit up to the value of the hard limit, and can only alter the hard limit down, not up.
Old 06-16-2013, 11:37 PM   #4
Registered: Jan 2006
Distribution: Slackware
Posts: 841

Original Poster
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Ok, I found it. I had created /sbin/initscript from /sbin/initscript.sample long ago, and updated it to raise the file descriptor hard limit. I dropped that modification when I did the full install from 13.37 to 14.0. I've updated my checklist to make sure I don't lose it again.

One other thing is that the location of initscript changed from 13.37 to 14.0. Up through 13.37 it had to be created in the /sbin directory, but as of 14.0, it has to be in /etc.


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