Well that was quick. We've only know that Valve is working on a version of Steam for Linux for a few months, but now it seems that the studio is ready to put that incoming version to the test. Valve will be putting Steam for Linux through and internal beta sometime next week, and then later on in October, it will invite a group of people to participate in a small private beta.
When we say "small" we mean it too. Valve will only be inviting 1,000 people to take part in this private beta, explaining in a Valve Linux blog post that the beta will involve Steam, one Steam game, and support for Ubuntu 12.04 and later. It appears that Steam for Linux is still in the early stages of development, at least relatively, as Valve says that the beta won't feature Big Picture Mode or any additional Steam games.
Valve didn't say what that one Steam game featured in this incoming external beta is, but we have a feeling it's Left 4 Dead 2. Valve has been using that game to test out Steam for Linux internally, so it makes sense that the studio would want to use it in the beta. Valve says that a beta sign up form will be coming soon, but didn't give an specific date for its release.
Valve also recommends that those who are new to Linux sit this beta out and instead sign up for a future beta. If you're an existing Linux users, however, Valve wants you, saying that this beta will be a good opportunity to see how far the studio has come in porting Steam to Linux. We'll have more details about this upcoming Steam for Linux private beta soon, so keep it here to SlashGear.