If you have problem with Apache 2.4, where the server reboot the service itself and no longer restart.
This was the error that appears whenever you try to start it:

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In addition, systemd reported the same problem:
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The cause is shown in the first error message:
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If we traced this, we noticed the directory /run/httpd no longer existed.
The simple fix in this case, was to re-create that missing directory:
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The directory should be owned by root and writable for the root user. The Apache group (usually httpd), needs executable rights to look into the directory.
Tag: Apache Failed to create shared memory, Centos7