Parallel installation of two versions of Mathematica on Linux

What that knowledgebase article doesn't tell you is that the installer won't blindly overwrite the symlinks in /usr/local/bin (well, not unless you set options to make it do that). So if the installer finds exisiting (symlinks to) executables in /usr/local/bin, it will ask you whether to overwrite or rename the existing links. Choose rename, and give them some sensible suffix (I use 1130). Then math and mathematica will refer to your most recently installed version, and older versions will have specific names. This is how I managed the more than 20 versions of Mathematica I have installed on my machine...

Also, the installer has a help message with brief descriptions of automation options for calling the script, which are useful if you'll be installing on a large number of machines. Do ./MathInstaller -help. (If you use the self extracting installer script rather than the CD image, it has a separate set of options for the extraction stage. Do ./installer.sh -help.)