As of today the Steam client for Linux is only offered in 32-bit format. It can be easily installed on 64-bit distributions such as Fedora 18 by the help of the 32-bit dependencies which are available in the OS package repositories, but to fully support Steam on 64-bit Linux you also need to configure the 32-bit version of the Adobe flash plugin which is used by Steam to display flash content within the application.
I’ve found several online guides to manually download the 32-bit version of flash and sym-link it to the firefox plugin folder (which is read by Steam apparently), but I prefer the yum way which is more elegant and it has one important feature: it takes care of (security) updates automatically.
Here’s how to setup the 32-bit Adobe flash plugin on Fedora 18 64-bit:
Install the 32-bit Adobe repository
sudo yum install linuxdownload.adobe.com/adobe-release/adobe-release-i386-1.0-1.noarch.rpm
Install the 32-bit flash plugin
sudo yum install flash-plugin.i386
Create a symbolic link in the Steam user path:
mkdir -p ~/.local/share/Steam/ubuntu12_32/plugins/
ln -s /usr/lib/flash-plugin/libflashplayer.so ~/.local/share/Steam/ubuntu12_32/plugins/
That’s it. Steam will now always load and use the latest version of the 32-bit flash plugin provided that you update the OS.
Note that having both the 32-bit and the 64-bit packages installed won’t create any conflicts, there are files shared by both variants (such as the icons) but they can easily co-exist on the same machine as long as both rpm packages have the same version number. As of now I have these packages installed:
$ rpm -qa | egrep 'flash-plugin|adobe'