Note: I originally asked this on Server Fault and was told it was against the rules for mentioning Webuzo, so please do not ask me to take it there.
System: VPS running CentOS 7 and Webuzo. httpd and sendmail had both been configured, but I wanted to add Roundcube for webmail.
Backstory: I first tried installing Roundcube from the command line. I attempted to follow these instructions but when I put Roundcube in my document root directory, I still got a 404.
I uninstalled the maria-db server and mysql packages, and then went to Webuzo to try to install it there. I was able to locate the installation page but got the error Database is not posted. I was unable to find any explanation of this error. My best guess is a necessary database port is blocked by my firewall, but I have no way to find out what the port number should be.
The problem: This afternoon, I discovered I was getting 404 errors for pages that had previously been accessible. httpd reported that it was unable to run due ot the port already being in use. I killed the process listening on port 80, then ran systemctl start httpd, but that didn't fix anything. Moreover, when that was running, Webuzo reported that the Apache server was actually stopped.
After more investigation, I found there was an extra copy of httpd that was now registered with systemctl. My guess is that something imported with the Roundcube-related packages brought it along. Stopping that and running the Webuzo version restored home-directory Web pages. I had to edit webuzoVH.conf to get my DocumentRoot setting fixed.