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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.

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strace -o loglimit su - abc and after that egrep "(limit|open)" loglimit, maybe your pam configuration are wrong –  c4f4t0r Jan 23 at 11:02
    
@c4f4t0r, the - option to su only causes a new login when it's the last argument. I only know this because I was just reading that man page. Also, as a detail, a regular user cannot strace an suid root binary. –  etherfish Jan 23 at 11:08
    
as root you need to use the command strace -o loglimit su - abc –  c4f4t0r Jan 23 at 11:14
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2 Answers 2

I suspect the ulimit is being applied by a /etc/profile or a ~/.bashrc. The fact that your system has a complicated pam, I would confirm that something isn't going awry.

I'd also confirm that there isn't an errant file in /etc/security/limits.d/ being parsed as mentioned in pam_limits(8).

I'd add debug parameter to the session required pam_limits.conf line and then watch /var/log/auth.log as you log in.

If your soft limit is 1024, whats your hard limit?

su should get you a fresh, new log in with su using the -l argument.

su -l -s /bin/bash

Good Luck.

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my hard limit is 4096 i.e ulimit -Hn –  Nerrve Jan 23 at 11:23
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On Redhat server logged as root

/etc/security/limits.conf

user01  -       nofile  2048

strace command logged as root

strace -o loglimit su - user01

with other shell open loglimit

grep "limit" loglimit
open("/lib64/security/pam_limits.so", O_RDONLY) = 6
 ..........
 ..........
 open("/etc/security/limits.conf", O_RDONLY) = 3
 read(3, "# /etc/security/limits.conf\n#\n#E"..., 4096) = 1823
 open("/etc/security/limits.d", O_RDONLY|O_NONBLOCK|O_DIRECTORY) = 3
 setrlimit(RLIMIT_NOFILE, {rlim_cur=2*1024, rlim_max=2*1024}) = 0

I this way i know that, pam_limits was loaded and limits.conf was readed, if your pam_limits was loaded but you still see other values using ulimit -n, check your shell profile as @etherfish told

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