You does not need to use Firefox in order to use the onion router. I am using
Tor around one year and have it always turned on, even now. Assuming you are
using Trisquel 5.0 with Abrowser, just follow my installation procedure
described here:
Open Terminal (with [Ctrl]+[Alt]+[T]), then write:
$ sudo add-apt-repository 'deb http://deb.torproject.org/torproject.org natty
main'
$ sudo apt-key adv --keyserver pgp.mit.edu --recv-keys 886DDD89
$ sudo apt-get update;sudo apt-get install vidalia polipo
$ A=vidalia.desktop;ln -s /usr/share/applications/$A ~/.config/autostart/$A
Now, install Torbutton and reboot.
You can check if your browser is configured properly by clicking here.
I also recommend you to use 'Peerguardian Linux' which blocks the access of
anti-P2P organizations to your PC.