我在ubuntu14.10中没碰到过这个问题，但在xubuntu14.04LTS中碰到
Steam needs to install these additional packages:
libgl1-mesa-dri:i386, libgl1-mesa-glx:i386, libc6:i386
[sudo] password for XXX:
OK，上解决办法：
sudo dpkg --add-architecture i386
sudo apt-get update
sudo apt-get install libgl1-mesa-dri:i386
sudo apt-get install libgl1-mesa-glx:i386