Max open file descriptors tuning

From Grid5000

Max open file descriptors must be increased to 8192 to allow some experiments to perform well. By default, most of the Linux distribution set this limit to 1024. To view current max open file descriptors limit value:

ulimit -n

This limit can be dynamically changed:

ulimit -n 8192

Upon connection thru oarsub or oarsh

To make this change permanent, ulimit -n 8192 must be added to

debian&co

/etc/default/oar-node

redhat&co

/etc/sysconfig/oar-node

Upon connection using ssh (OAR2 -t allow_classis_ssh)

To make this change permanent, /etc/security/limits.conf file must be edited:

*                hard    nofile          8192
*                soft    nofile          8192

This file is used by pam and its module pam_limits. To be sure this module is loaded please see:

/etc/pam.d/sshd and /etc/pam.d/system-auth on Redhat-based system
/etc/pam.d/ssh and /etc/pam.d/login on Debian-based system

	Warning
	If `sshd` is configured to use privilege separation, `pam_limits` becomes partially inoperative, because it is not run as `root`. A workaround is to dynamically change limit (ie. `ulimit` `-n`) in start section of `sshd`'s init.d script. By doing this, `limits.conf` becomes useless. Moreover watch out `sshd`'s init script during system package upgrade.