So you got this error :

No space left on device: AH00023: Couldn’t create the ssl-cache mutex
AH00016: Configuration Failed

This relates to “semaphores” on your system (you’ve run out).

Semaphores can be thought of as simple counters that indicate the status of a resource. This counter is a protected variable and cannot be accessed by the user directly. The shield to this variable is provided by none other than the kernel. The usage of this semaphore variable is simple. If counter is greater that 0, then the resource is available, and if the counter is 0 or less, then that resource is busy or being used by someone else. This simple mechanism helps in synchronizing multithreaded and multiprocess based applications. Semaphores were invented and proposed by Edsger Dijkstra, and still used in operating systems today for synchronization purposes. The same mechanism is now available for application developers too. Its one of the most important aspects of interprocess communication.

How to fix  ?
In your ssh console / root execute following commands:

ipcs | grep apache | awk '{print $2}' > sem.txt

for i in `cat sem.txt`; do { ipcrm -s $i; }; done;

If this becomes a common occurance, then you may need to change your ipcs semaphore limits by setting the following in your /etc/sysctl.conf:

kernel.msgmni = 1024
kernel.sem = 250 256000 32 1024

Keep it real ,
Best Regards ,Alin Razvan
I'm a small fish in a big ocean , trying to make a difference and some waves while swimming my way through .

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