Q:

Problems with su: Authentication Failure

I am currently using Ubuntu and am 100% new to Unix. I have installed Ubuntu to program in C and will be using the "Learn C the Hard Way" online textbook (http://c.learncodethehardway.org/book/ex0.html). I attempted the section in the textbook meant for setting up your computer and the second command is causing me some problems.
The first command in the link above executes without issue but when I try and run the second command:
$ su -c yum groupinstall development-tools

it prompts me for my password and when I enter it, it says 

su: Authentication Failure

How do I fix this?

A:

Look again at the web page. You are trying, wrongly, to run a command for an RPM based Linux like Fedora. Instead, run the command that says:
For Debian based systems, like Ubuntu you should just have to install a few things using these commands:
$ sudo apt-get install build-essential

