Why doesn't man work?

You run man followed by whatever it is you need the manual for. So for example: man ufw Some packages don't have a man page.

I ran man ls
And nothing

What is the output of these commands:

command -V man
ls -l /usr/share/man/man1/ls.1*
man ls

'man' will respond with "No manual entry" if you do not have the software installed--Once you have installed the software, you should be able to use the 'man' command on that particular software, as the man pages are installed during the software installation (apt-get install).

• Example of man with ufw not installed

$ man ufw
No manual entry for ufw

• Example of man on ufw after the installation

$ apt-get install ufw
$ man ufw
NAME
       ufw - program for managing a netfilter firewall
... output omitted ...

However, if you are receiving the following error message when you are attempting to use 'man' then it could mean it is not installed.

$ man man
-bash: man: command not found

In this case, I would recommend installing 'man' with the following command.

$ sudo apt update && sudo apt upgrade && sudo apt install man

I hope this helps.

Thanks Ferez, installing man did the trick!