"Firefox is already running" with -no-remote

The -no-remote option is used for running multiple Firefox profiles at the same time. You are getting the "Firefox is already running" message because you are trying to open a second Firefox instance with the same profile.

You should be using this option as follows:

firefox -no-remote -P "Another Profile"

or

firefox -no-remote -profile "profile_path"

where profile_path is an absolute or relative (to firefox.exe) path.

I had the same need like you : running many instances of firefox on the same machine.

Basically, when you run an instance of firefox, there is a folder .mozilla in your $HOME is created ( if it is not existed yet). You can use the multi-profile solution if you want, as iglvzx mentioned above. So all user's profiles live in that .mozilla directory(database).

I have another trick which I think is more elegant than that solution. Create a directory to save a new firefox:

$ mkdir $HOME/new_firefox

$ cd $HOME/new_firefox

$ tar xvf setup/firefox-33.0.tar.bz2

Then create a small script like:

#!/bin/sh
HOME=$HOME/new_firefox
$HOME/firefox/firefox -no-remote &

So now run the scrip to have another instance of firefox. And your new user's profile live in $HOME/new_firefox/.mozilla.

If you use GNOME, just create a new_firefox.desktop file and put it in /usr/share/applications directory or in $HOME/.local/share/applications directory. The Exec argument in that file is Exec=/home/your_name/path-to-your-script. If you don't know how to create one, see an existed one in either of 2 above directory.