What Linux distro/version is running

Most people know about uname -a to get a good amount of information. However, if you want an easy way to discover the distro/version you can run:

cat /etc/issue

The problem is that /etc/issue was never meant to keep track of the release version. So it may not exist on certain machines. I believe the most reliable method would be to:

cat /etc/*release

or

lsb_release -a