Re: Mac OS X + Linux
Commandline syntax for Linux, MacOSX, and Win is (are?) here: Mozilla Command Line Options.
Mac OS X syntaxes:
hold down Option key (Alt key) when launching FF
* go to "
/Applications/Firefox.app/Contents/MacOS", type "
* also, "firefox -?" or "firefox --help" should show you the full list of options; chances are the shorter "-P" is also implemented for macosx
* Browser: type
About:Profiles into URL-bar, configure as desired