https://developer.valvesoftware.com/wiki/SteamCMD

Which Ubuntu and do you have non-free packages activated (and did an apt-get update afterwards)?

Whenever you are looking for a package on Ubuntu / Debian you can use the following command to try & track down the package in the repository when you don't know it's full name ect ..


COMMANDS:

su

sudo apt-get update

sudo apt-cache policy steam*


That will list every package in the repository that contains the word steam. The more accurate you are about the package name the easier it is to find it.

You can do ..

sudo apt-cache policy steamcm* for example .. assuming those letters are part of the package name.


Lastly, you can Google the Ubuntu packages online & check to see what repository contains the package you require.


Here ..

https://packages.ubuntu.com/


You would then add the repository to your system and update the package manager before searching for the package again.


The following command will install "gedit" and "nano" packages which allow you to use either one to edit the "sources.list" file which contains the Ubuntu repository links.


sudo apt-get install gedit nano -f


sudo nano /etc/apt/sources.list

or

sudo gedit /etc/apt/sources.list


There you will find the repository links that are currently available for your system. If you add or disable one you must save the changes and run . ..

"sudo apt-get update" ( Without the quotes ) to ensure the package manager will see the changes you made there so that the system can find files that may be located in the repository links you have added or enabled.


This directory also contains repository links when they are imported via the command terminal.


cd / etc/apt/sources.list.d && ls


You might see some configuration files there directly related to various repositories.