My environment is Windows 7==>Oracle Virtual Box==>Ubuntu. I am still struggling with FQDN. I posted on the subject previously here.

Well, after some reading and contemplations I figure that I need to enter a couple of lines in the file /etc/hosts.

The result is in the first thumbnail. I used the lines the user chrism01 gave to me:

Then I updated the system and so what? An attempt to install Gfortran gives me the same error: "I need a FQDN."

Why do people give me suggestions that do not work?

The result of the attempt to install GFortran is in the second thumbnail.

Can I get sensible, detailed instructions from someone who knows how to do it?

Thanks, - Alex

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You misunderstood that, it was just an example of lines in /etc/hosts.
It seems to me that you know very little about networking, fqdn and such. That wiki page chrism01 linked to is good but probably a bit over your head. I'll try to be very clear:
In /etc/hosts you add entries that are supposed to be resolved, it is like a small DNS server. If you add a line "192.168.1.2 www.yahoo.com" to /etc/hosts and then in a browser writes url "www.yahoo.com" you will not get Yahoo - you'll reach a server with ip 192.168.1.2.
Some applications, like apache, searches /etc/hosts for a fqdn.
The actual hostname your computer has is written in /etc/hostname (Using LinuxMint now).

Now, looking at your pictures, your second snapshot tells me what you need: "The hostname -f returned ..."
"hostname -f" reads from /etc/hostname not /etc/hosts

So you need to do this:
Set a correct hostname, edit /etc/hostname and restart network or use some GUI-tool to change the hostname. (Don't know what tools Ubuntu has.)
Then try installing again - you could use "sudo apt-get -f install"

pingu, Thank you very much. I actually have a domain name, I figured, which is my last_name.org. I use it for emailing. Can I sue that?

I appreciate a thorough explanation though. Thanks, - Alex

Well, then you could use a fqdn like "alexb.last_name.org"

Those 2 lines I gave above are for the machine to talk to itself (yes, that's not a typo).
Certain processes use that info, so do keep those at the top of /etc/hosts, then append any other reqd lines.

In your case it looks like Ubuntu provides the equivalents already, plus others.
Do ensure you don't have duplicate entries.

pingu and chrism01, thank you very much. - Alex