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Old 08-06-2009, 04:28 AM   #1
Registered: Mar 2008
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How to set these linux parameter

hi ppl,

i was told by my vendor to add in these parameters in my redhat 4 and 5 servers

Parameter Value Description
semmns 640 Max Number of Semaphores
semmni 64 Number of Semaphore Identifiers
Semmap 66 Max Number of Semaphore Map Entries(semmni+2)
Semmnu 640 Number of Semaphore Undo Structures
semume 30 Semaphore Undo Entries per Process
Shmmax 20000000 Max Shared Mem Segment (bytes)
Shmall 40000000 Max Shared Mem Segment (bytes)

i put in /etc/sysctl.conf and run sysctl -p. i got this error
kernel.shmmax = 68719476736
kernel.shmall = 4294967296
error: "kernel.semmns" is an unknown key
error: "kernel.semmni" is an unknown key
error: "kernel.semmap" is an unknown key
error: "kernel.semmnu" is an unknown key
error: "kernel.semume" is an unknown key

is that the correct place to input them?

Kindly assist. Really appreciate
Old 08-06-2009, 08:41 AM   #2
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You can determine all settable parameters by running "sysctl -a".

Running "sysctl -a |grep sem" you'll see only kernel.sem.

Semaphore related parameters in Linux are all set with kernel.sem.
kernel.sem parameter has multiple values in the format:
'semmsl semmns semopm semmni'

So you'd need to find your current values by typing:
sysctl kernel.sem which should produce something like:
kernel.sem = 250 32000 32 128

You then add a line to sysctl.conf like:
kernel.sem = 250 640 32 64

I wouldn't actually do that though - my rule of thumb is to set parameters higher than defaults if required but not lower. Typically the vendor just wants enough to insure their application will run. The defaults are much higher than they're requesting.

However the fact they are telling you to set parameters not relevant to Linux and NOT telling you to set some that are means they don't know Linux. Have they indicated their application runs on Linux?

Also check the kernel.shmmax. I've often seen vendors suggest setting this value based on the memory of the system they did their development on and completely ignore the fact your system may allow for more or less than that.


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