Fixing: apt-get install mc is not available error on Ubuntu
So you’ve just installed Ubuntu 16.04, you’ve configured networking and it works properly but when you want to install Midnight Commander (or other package) you get an error:
apt-get install mc is not available
To fix the problem run first apt-get update command:
sudo apt-get update
Then try to install mc:
sudo apt-get install mc
Of course there could be other reasons (like your /etc/apt/sources.list file missing or containing wrong links to package repos) but on a default Ubuntu installation this could fix the problem).