I have just configured a new server that keeps dying from time to time. The error log indicated the following problem:

[Thu Feb 11 03:21:15.261690 2016] [mpm_prefork:emerg] [pid 1273] (43)Identifier removed: AH00144: couldn't grab the accept mutex
[Thu Feb 11 03:21:15.640431 2016] [core:alert] [pid 1256] AH00050: Child 1258 returned a Fatal error... Apache is exiting!

I tried the solution listed here (basically to add AcceptMutex flock to httpd.conf) , but Apache wouldn't start:

Invalid command 'AcceptMutex', perhaps misspelled or defined by a module not included in the server

So now I don't know what else to do.


If you go back and look at the page you linked to, there's a line a little bit further down that says:

With apache 2.4, use Mutex instead of AcceptMutex

  • Well...I feel so stupid. – carla Feb 12 '16 at 14:35
  • 1
    @carla Been there, done that... – Jenny D Feb 12 '16 at 14:59

Try adding

AcceptMutex posixsem

in your apache conf

  • Yes, I tried, and the same "Invalid Command" message appeared when I tried to restart Apache. – carla Feb 12 '16 at 14:23
  • 1
    @carla if you use apache 2.4 Mutex posixsem – ZiTAL Jul 14 '18 at 15:09

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