I am running Linux: LMDE Cinnamon Edition - 64 bit I am using firefox version Mozilla Firefox 31.0 I wish to have two instances of FF running. One with my standard, personal settings and a second instance that ONLY connects to Facebook and will stop data leaking between the two. I can acheive this by opening Facebook in another browser (e.g. Chrome or Opera). I checked the ProfileManager under Firefox and created a second profile called "FB". I can run firefox -p FB and it will open an instance of FF with none of my personal settings available - that's what I was hoping for. However, if I run a second instance of FF - for example from the command line as firefox -p default it loads with the same profile as the first instance I opened, not the new profile as specified in the command. I can only select the profile if there are no prior firefox instances running under my user-id. The first instance defines which profile is used for all subsequent executions - no matter which profile I specify on the command line. Even running firefox -ProfileManager will start with the first-specified profile, not the profile manager.