When I enter the command in Terminal.app as shown in the article, replacing italicized text with my specific info, I get:
WARNING: Improper use of the sudo command could lead to data loss
or the deletion of important system files. Please double-check your
typing when using sudo. Type "man sudo" for more information.
To proceed, enter your password, or type Ctrl-C to abort.
This worries me. I have never used Terminal.app and am new to running my own server. I have a Mac Mini Server, running a netboot for 24 student computers. My server alerts tell me the certificate has expired and is expiring. I have also been having problems with students not being able to access a shared folder that I put resources in for their projects. I don't know if the two are related, but wanted to give as much info as possilbe.
The alert is baked in. It is designed to make you think before committing commands as sudo. This is effectively executing actions as root. If you know what you are doing, then enter the command with confidence. Screwing up as root could take down the whole server. Classic case... sudo rm -R * in the wrong place can make for a really, really bad day.
Regarding your certificates, open Server.app and take a look at what you have. If you are using the self-signed, you may not even be using it for any services. If this is the case, then let it expire. If you are using a purchased cert, and it is active on services, then renew it.
And for students not accessing the shared folder, what is the behavior that the student sees? Permissions denied? No connectivity?