I've done the usual edit of /etc/sysctl.conf to include the parameter, but it just tosses errors. I haven't had to tune a kernel in a very long time, what's different about it nowadays (or have I simply forgotten how)?


Added "kernel.semmni = 2048" to the tail of /etc/sysctl.conf and then ran "sysctl -p". End result is an unknown key error (apparently kernel.semmni isn't the valid name anymore?).

  • OK, this doesn't work under Oracle Enterprise Linux either. There's got to be a way to change the number of system wide semaphores available, the default 128 is ridiculously low. Any more ideas? Sep 24, 2010 at 13:04

2 Answers 2


You can see the list of valid sysctl params with sysctl -a. I'd run that, see if it's changed in your newer kernel

  • Helpful, I was completely overlooking that option. "semmni" is not a valid option on this kernel. Rather unfortunate, since the software I'm trying to install says that I need to bump it from 128 up to 2048... Argh. Sep 14, 2010 at 15:00

Finally got it. Desipite what everything I found on Google suggested, semaphores aren't individually settable, they're all bundled together under "kernel.sem". Added:

kernel.sem=250 32000 100 2048

to my /etc/sysctl.conf and I'm in business!

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