Apache HTTPD: Address already in use: make_sock: could not bind to address 0.0.0.0:443

During my latest Apache configuration change I ran into an issue where I wasn’t able to restart/start. This was the first time I encountered this and I was fairly positive the issue wasn’t due to my configuration changes. I also knew that a port can only be used by one application or daemon at a time so that clued me in that something else was already using the port. While I can’t give a definitive cause for the situation, I can give pointers on resolving the issue. Note that this pertains to Apache running on Linux so your mileage may vary.

Here’s what I encountered after I ran the ./apachectl start command:

(98)Address already in use: make_sock: could not bind to address 0.0.0.0:443
no listening sockets available, shutting down
Unable to open logs

To solve the issue I first tried the following to see if there were some running httpd processes that shouldn’t have been running at this point:

This revealed no processes running. Next I tried netstat and that didn’t reveal anything either. Then I decide to view all processes with ps -aux, and after close inspection found the culprit:

root      5004  0.0  0.0  4384    4 ?        S    Apr25   0:00 bash
mysql     5095  0.0  0.7 41968 7980 ?        S    Apr25   0:47 ./mysqld --user mysql
apache    7323  0.0  0.0 3014368  0 ?        TW   Apr25   0:01

There was a phantom process (line 3 above) running as the apache user but didn’t have a command associated with it. Knowing that nothing else on the server runs as the apache user, I decided to kill the varmit:

After doing this, I was able to start the apache server again.

Has anyone else run into this issue and more importantly why it happened?