Free Software Server Environment: Resource Limits

Resource Limits

resource limits are defined for each shell and its processes there are hard limits and soft limits

ulimit

ulimit -{H|S}a displays your current resource limits

$ ulimit -Ha

core file size        (blocks, -c) unlimited
data seg size         (kbytes, -d) unlimited
file size             (blocks, -f) unlimited
max locked memory     (kbytes, -l) 4
max memory size       (kbytes, -m) unlimited
open files                    (-n) 500
pipe size          (512 bytes, -p) 8
stack size            (kbytes, -s) unlimited
cpu time             (seconds, -t) unlimited
max user processes            (-u) 7168
virtual memory        (kbytes, -v) unlimited

$ ulimit -Sa
core file size        (blocks, -c) 0
data seg size         (kbytes, -d) unlimited
file size             (blocks, -f) unlimited
max locked memory     (kbytes, -l) 4
max memory size       (kbytes, -m) unlimited
open files                    (-n) 300
pipe size          (512 bytes, -p) 8
stack size            (kbytes, -s) 10240
cpu time             (seconds, -t) unlimited
max user processes            (-u) 7168
virtual memory        (kbytes, -v) unlimited

resource limit defined

your resource limits are defined and can be changed in a number of files !

/etc/sysctl.conf

kernel.shmall = 2097152
kernel.shmmax = 536870912
kernel.shmmni = 4096

/etc/security/limits.conf

you must enable ulimits for user in security.conf !

myuser hard nproc 16000
myuser soft nproc 2000
myuser hard nofile 65000
myuser soft nofile 1000

/etc/profile

if [ $USER = "myuser" ] ; then
		ulimit -u 10000
		ulimit -n 65000
fi

.bash_profile

ulimit -n 60000

.bashrc

ulimit -n 50000

/etc/bashrc

ulimit -n 40000

ulimit problems

you may not be able to use ulimit to INCREASE your resource limits
if you are using SSH to connect to your server you may not even be able to use ulimit at all and might get an error as soon as you connect/login if there is a ulimit command in one of your startup scripts (unless you disable SSH PrivilegeSeparation) !
ulimit switches are different in bash and ksh

trying to increase a ulimit

$ ulimit -n 8000
-bash: ulimit: open files: cannot modify limit: Operation not permitted

/etc/ssh/sshd_config

#UsePrivilegeSeparation yes
UsePrivilegeSeparation no

Free Software Server Environment : ResourceLimits