Invalid Mutex directory in argument file:${APACHE_LOCK_DIR}
Solution 1:
I ran into this once and this worked for me:
source /etc/apache2/envvars
apache2 -V
sudo service apache2 restart
I haven't had the problem since.
Solution 2:
That looks like you tried to start Apache by running something like
apache2
That doesn't work. Use
sudo service apache2 start
instead.