===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===
1) you may not be able to use ulimit to INCREASE your resource limits
1) 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) !
1) 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
%%

==see also==
PluggableAuthenticationModule
UlimitSwitches

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REFERRERS
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