handling Apache cannot start: "(28)No space left on device: Cannot create SSLMutex"

Today I tried to start apache server using below command

/etc/init.d/httpd2 start

It shows  Starting httpd:                                            [  FAILED  ]

I started debugging and opened apache log which shows me following error.

[Tue May 03 17:08:18 2016] [info] Init: Seeding PRNG with 136 bytes of entropy
[Tue May 03 17:08:18 2016] [info] Init: Generating temporary RSA private keys (512/1024 bits)
[Tue May 03 17:08:18 2016] [info] Init: Generating temporary DH parameters (512/1024 bits)
[Tue May 03 17:08:18 2016] [error] (28)No space left on device: Cannot create SSLMutex
Configuration Failed

REASON
 
This type of error comes when there is a lack of inner-process communication resources in the system, such as semaphores or shared memory segments:

We can check this by following command

ipcs -a

sample output is as blow.

------ Shared Memory Segments --------
key        shmid      owner      perms      bytes      nattch     status

------ Semaphore Arrays --------
key        semid      owner      perms      nsems
0x00000000 14614528   webdoc    600        1
0x00000000 14647297   webdoc    600        1

------ Message Queues --------
key        msqid      owner      perms      used-bytes   messages

RESOLUTION

use command below to delete memory segment used to free up space, so that inner process communication can get resources to run apache service

ipcs -s | grep webdoc | awk '{print $2}' | xargs ipcrm sem

after running this command you can now  start apache

/etc/init.d/httpd2 start

It shows  Starting httpd:                                            [  OK  ]