A linux distro (distribution) is a complete, installable operating system based around the Linux Kernel.
There are some that are especially good for dedicated MythTV boxes (the kind you'd have on a HiFi stand in the lounge), others are especially suited for use as workstation PCs -- though you can use them to run MythTV as well, if you're sufficiently motivated.
Here's an alphabetic list...
Debian is a widespread distribution, Debian has a huge community and is probably the most 'free' and socially driven distribution - an excellent choice and MythTV is well supported. There are a couple of guides:
- Mythtv Installation Guide for Debian
- Debian Guide
- Another Debian Guide
- A.M.I.C.U.S. - The automatic installation script. An introductory guide with menu script specifically designed for new users of GNU/Linux and/or MythTV. Minimal hardware requirements and suitable for older/low end PCs.
Fedora is a very popular distro - especially well supported by the famous Jarod's Guide. Some work is also being done to write a single "kickstart" script based from Jarod's Guide. You can find this script at 
There is also the Fedora Core2 Guide
Here is a pointer to some resources: Fedora_Core2
FreeBSD - Stacey Son has provided a FreeBSD port of MythTV
Gentoo - If you are scared of command prompts, Gentoo is not for you. On the other hand the installation is extremely well documented in the Gentoo Handbook. Gentoo is more customizable than other 'binary' distros and each install can be optimized to the specific processor you use.
Gentoo MythTV setup guides:
Official Gentoo MythTV Guide:
- MythTV on Gentoo - currently Incomplete
Kanotix is one of the many Debian based Live CDs, which itself is based on the popular Knoppix Live CD, except Kanotix has the ability to be easily installed on to a harddrive, from which a fully working easy to maintain Debian system is had.
Knopp Myth is probably the easiest way to install MythTV. After all - that's what it was made to do. It's mainly oriented towards dedicated Myth boxes (though of course it runs a complete GNU/Linux OS so no worries about serving music or other files). Insert the CD into a 'blank' PC and you'll be running Myth after a few minutes. It's Debian based and, as a special trick, MythFrontend will run from the CD without installing. (Also see the Knopp Myth page).
While The Macintosh OS is not actually Linux, MythTV runs there, too. Open Darwin is a distribution that runs on Mac hardware - the Myth On Mac Osx guide is right here on Mythtv.info :) Also here is OS-X Frontend build instructions
- There's also the Setting up MythTV under Mandrake 10.1 Guide
- The MythTV How-To wikibook uses Mandrake as an example
Mini Myth boots over a network and runs MythFrontend on diskless Via EPIA M systems. (ie you need another 'proper' machine too!) This is great for 'satellite' systems - like having one in the bedroom or kitchen...
Slackware is one of the eldest linux distributions and still going strong. Historically often used for servers. Some of the MythTv users use this for both backend as well as frontend purposes.
Suse, A Popular distro in Europe and the US. Known for it's YaST installer. The company was recently purchased by Novell.
Ubuntu is a Debian based solution.
- Ubuntu Hoary Installation - A step-by-step guide for setting up MythTV on Ubuntu Hoary (5.04)
- Ubuntu Breezy Installation - A step-by-step guide for setting up MythTV on Ubuntu Breezy (5.10)