Apache 2.4 AH01762 & AH01760: failed to initialize shm (Shared Memory Segment)

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Mattias Geniar, January 12, 2016

Follow me on Twitter as @mattiasgeniar

I recently ran into the following problem on an Apache 2.4 server, where after server reboot the service itself would no longer start.

This was the error whenever I tried to start it:

$ tail -f error.log
[auth_digest:error] [pid 11716] (2)No such file or directory:
   AH01762: Failed to create shared memory segment on file /run/httpd/authdigest_shm.11716
[auth_digest:error] [pid 11716] (2)No such file or directory:
   AH01760: failed to initialize shm - all nonce-count checking, one-time nonces,
   and MD5-sess algorithm disabled

Systemd reported the same problem;

$ systemctl status -l httpd.service
 - httpd.service - The Apache HTTP Server
   Loaded: loaded (/usr/lib/systemd/system/httpd.service; enabled; vendor preset: disabled)
   Active: failed (Result: exit-code) since ...

The cause is shown in the first error message: Failed to create shared memory segment on file /run/httpd/authdigest_shm.11716.

If I traced this, I noticed the directory /run/httpd no longer existed. The simple fix in this case, was to re-create that missing directory.

$ mkdir /run/httpd
$ chown root:httpd /run/httpd
$ chmod 0710 /run/httpd

The directory should be owned by root and writeable for the root user. The Apache group (in my case, httpd), needs executable rights to look into the directory.

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