Get SteamOS Beta running on VirtualBox
This step by step guide will easily let you install Steam OS beta on virtualbox. However, please be aware that a VM will not exhibit the same performance level as a bare installation. Gaming (of any type) is likely to be awful. It's fine to try out the install though and have a good overview of the OS. You could try out how to setup a dual boot on your machine for example.
Download SteamOS beta (http://repo.steampowered.com/download/SteamOSInstaller.zip).
You get a zip file which you need to unzip to then create an iso.
To create the iso from the SteamOSInstaller folder, run:
xorriso -as mkisofs -r -V 'Steam OS' -o /tmp/SteamOSInstaller.iso -J -joliet-long -cache-inodes -no-emul-boot -boot-load-size 4 -boot-info-table -eltorito-alt-boot -append_partition 2 0x01 /tmp/SteamOSInstaller/boot/grub/efi.img -partition_offset 16 /tmp/SteamOSInstaller
The above commands believes you have the SteamOSInstaller you extracted from the zip in the /tmp folder
Then in VirtualBox, create the New button to create a new VM.
Name it Steam OS for example
Choose Type = Linux and Version = Debian (64 bit)
Select 2048Mb of RAM
Create a virtual hard disk with 500Gb
Now go in the settings of this VM, then Storage and in Controller IDE, click on Empty, click on the little CD, click Choose a virtual CD/DVD disk file... and select the SteamOSInstaller.iso created before.
Now click on System in the left menu and tick the box Enable EFI.
Finally, click on Display in the left menu and tick the box for 3D Acceleration and choose the amount of memory you want to allocate.
You can now start the VM, the installer will start and you can choose Automated Install (WILL ERASE DISK)
Now, drink a cup of tea while the install is being done.
When install is finished, you will be asked to click a Continue button to reboot, you should then see the grub bootloader with Steam OS entry, select the entry with recovery mode.
You are now on a shell, you need to uninstall nvidia packages, so you run:
apt-get remove xserver-xorg-video-nvidia nvidia-driver glx-alternative-nvidia libgl1-nvidia-glx libnvidia-ml1 nvidia-alternative nvidia-installer-cleanup nvidia-kernel-common nvidia-kernel-dkms nvidia-support nvidia-vdpau-driver
apt-get purge ".*nvidia.*"
Give a password to the desktop user:
Click on Devices -> Insert Guest Additions CD image...
Once that's done, mount it:
And run the install script for the guest additions
You now choose the first entry in grub (and not the recovery like before), it boots, you can login with the desktop user and you can now run Steam (alt + f2 -> steam -> enter).
If you shutdown the VM and end up in the EFI shell, then you can type the following:
To avoid having to type that line, you can add a file /boot/efi/startup.nsh with the line above in it. You can do this from the EFI shell directly:
You write EFI\steamos\grubx64.efi and press ctrl + s, press enter and ctrl + q to quit.