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How can I increase the number of semaphores?

Postby chandranjoy » Wed Sep 01, 2010 8:54 pm

A Red Hat Enterprise Linux Server running Apache crashes after about a day or so of running. Using the ipcs command it was discovered that the server crashes once Apache has used 100 out of 128 semaphores.


Before beginning, check the defaults so they can be referenced later. To view the current semaphore settings, use the cat command:

# cat /proc/sys/kernel/sem
250 32000 32 128

The following is an example of how to make these adjustments permanent.

Edit the /etc/sysctl.conffile by adding:

kernel.sem = 250 32000 32 256

Note: the '=' (is (space)=(space)) - spaces are important in this file. There should be a space before and after the equals (=) sign.

Issue the sysctl -p command to make these changes take effect immediately. Setting the values in this file will also save them for future system reboots.

Enjoy :)
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