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Yuri Ushakov's questions

Martin Hope
Yuri Ushakov
Asked: 2015-06-11 04:22:09 +0800 CST
  • 2

Debian 8.0, pam 1.1.8-3.1, sshd 1:6.7p1-5.

I'm trying to permanently increase the maximum number of open files.

In /etc/pam.d/ I've got:

/etc/pam.d# grep pam_limits.so *
atd:session    required   pam_limits.so
common-session:session required pam_limits.so
common-session-noninteractive:session required pam_limits.so
cron:session    required   pam_limits.so
login:session    required   pam_limits.so
runuser:session         required        pam_limits.so
sshd:session    required     pam_limits.so
su:session    required   pam_limits.so

In /etc/security/limits.conf:

*       hard    nofile  20000500
*       soft    nofile  20000500

In /etc/ssh/sshd_config:

UsePAM yes

In /etc/sysctl.conf:

fs.file-max = 20000500

I've rebooted the OS and what I'm seeing in /var/log/auth.log is:

sshd[807]: pam_limits(sshd:session): Could not set limit for 'nofile' to soft=20000500, hard=20000500: Operation not permitted; uid=0,euid=0

Same thing trying to do ulimit -Hn 20000500 as root:

bash: ulimit: open files: cannot modify limit: Operation not permitted

Using trial-and-error, I've found the maximum number I can give ulimit -Hn without failing: 1048576. Why exactly this number and where does it come from?

P.S. When it says "operation not permitted", how do I know who decides? I assume the code within pam_limits.so is trying to set the limits, but who does actually refuse? Is it the PAM system which possibly takes over the whole security system in the OS?

ssh
Martin Hope
Yuri Ushakov
Asked: 2011-02-15 01:18:21 +0800 CST
  • 85

We switched from PostgreSQL 8.3 to 9.0. Perhaps it's a new feature or perhaps just a configuration change, but now when output from commands (like, \d tablename) exceeds visible vertical space, psql seem to pipe the output through something similar to less. I could not find a way to turn this behaviour off. Any advice? Thanks.

P.S. I'm scrolling the buffer using PuTTY's Shift+PgUp/PgDn so I don't need psql's paging. Plus, when I press q in the psql's paging, its output disappears from the screen entirely (just like after running less in bash), which is wrong from the general use-cases point of view.

psql