Normally you know which version of a given distro you are running if you are on your machine, but what if you are on a rented server, or a friend’s machine.
If you want to know which version of Debian or Ubuntu you are running, you can always check the
/etc/apt/sources.list there you will see the version you are running but a better way is to run this on a terminal:
The output in my Debian Box is:
Distributor ID: Debian Description: Debian GNU/Linux 5.0 (lenny) Release: 5.0 Codename: lenny
You can also run this in a Debian Linux.
In my Debian box this is the output:
I do not have an Ubuntu machine now, but I can remember that if you run this on an Ubuntu Linux, you will get
As the output, as Ubuntu is based on Debian sid.