Error : “Identifier removed: couldn’t grab the accept mutex” in apache error logs

Apache was getting stopped automatically with the below logs in the Apache Error log:

[Tue Jul 22 22:29:35 2014] [alert] Child 30758 returned a Fatal error… Apache is exiting!
[Tue Jul 22 22:29:35 2014] [emerg] (43)Identifier removed: couldn’t grab the accept mutex
[Tue Jul 22 22:29:35 2014] [emerg] (43)Identifier removed: couldn’t grab the accept mutex
[Tue Jul 22 22:29:35 2014] [emerg] (43)Identifier removed: couldn’t grab the accept mutex

These type of errors occur on systems low on memory or file handlers.The AcceptMutex directives sets the method that Apache uses to serialize multiple children accepting requests on network sockets.

One suggested resolution for the error message would be to try adding the following line to /usr/local/apache/conf/httpd.conf file:

AcceptMutex fcntl

If you add this above “<IfModule prefork.c>” in tht file, you could then try running these commands to distill the change and restart Apache:

/usr/local/cpanel/bin/apache_conf_distiller --update
/scripts/rebuildhttpdconf
/etc/init.d/httpd restart

Please check on the rebuild that the line you’d entered was maintained.

If you  are using Mod_ruid, then you may need to use the below as some users have encountered problems with mod_ruid2 while using mutual exclusion.

To solve this issue, add the following line to /usr/local/apache/conf/mod_ruid2.conf:

AcceptMutex posixsem

For more reference you may check the below links

http://docs.cpanel.net/twiki/bin/view/EasyApache3/ModRuid2
http://httpd.apache.org/docs/2.2/mod/mpm_common.html
http://forums.cpanel.net/f189/apache-2-crashing-252991.html

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