Howto always run privoxy within Firefox, with switching between tor on/off.
You have to run two Privoxy daemons in parallel.
You have Privoxy installed. Now You copy it's configuration directory to a second place:
cp -a /etc/privoxy /etc/privoxy2
In one config you forward to tor daemon (using Tor), in the other not (not using Tor). Second, the two Privoxys have to listen on different ports. So, if the first Privoxy listens on the standard port 8118, edit /etc/privoxy2/config and edit:
listen-address 127.0.0.1:8119
So the first listens on port 8118 and the second on 8119.
Now You have to create an init script for the second Privoxy. The following I have done for this in Debian Etch:
cp /etc/init.d/privoxy /etc/init.d/privoxy2
Then edit /etc/init.d/privoxy2:
NAME=privoxy2
CONFIGFILE=/etc/privoxy2/config
Now You have to add privoxy2 to the rc-directorys to start and stop automatically when entering runlevels:
update-rc.d privoxy2 defaults
and start it the first time manually:
/etc/init.d/privoxy2 start
Now You should have running two Privoxy processes (check with ps aux | grep privoxy).
Now install the Firefox switchproxy extension and configure it to switch between the two Privoxys (localhost:8118 and localhost:8119).
That's it!