Apache not start : device: AH01760: failed to create lock (client_lock)

This’s very likely that Apache leaving a bunch of stray semaphore sets
lying around after an attempted restart of apache.

you can use the following commands to check:
#ipcs -s | grep apache

and use the following to kill:
ipcs -s | grep apache | awk ‘ { print $2 } ‘ | xargs -n 1 ipcrm -s

use the username you starts apache (e.g., specified by “User” directive)
instead of ‘apache’ in the commands.

Device: AH01760: failed to create lock (client_lock) – all nonce-count che
cking, one-time nonces, and MD5-sess algorithm disabled

Now, in almost all cases, Apache should start properly. If it doesn’t, you may just be completely out of available semaphores. You may want to increase your available semaphores, and you’ll need to tickle your kernel to do so. Add this to /etc/sysctl.conf:

1 2	kernel.msgmni = 1024 kernel.sem = 250 256000 32 1024

And then run sysctl -p to pick up the new changes.