I have a tor service already running in a VM and I want TorBrowser uses that instance of tor instead start up another process in current machine. Is it possible? How can I do? What's the correct configuration of torrc in VM?
I wrote a guide for this, I was asked to transcribe it to the Tor Project wiki so that it was as easier to find resource (and so that I didn't have editorial authority over it).
You can find the wiki page here TorBrowserBundleSAQ, as far as I am aware there have been no changes to it since I originally transcribed it from my original version but edits, improvements and corrections are welcome and encouraged.
In short, there are specific environment variables that can be set that both Tor Button and Tor Launcher will use to decide how to act when starting up Tor Browser. In linux you can add these to your
/etc/profile or as a file in
/etc/profile.d/ or add them to the start-tor-browser script itself. They just need to be set in the environment variables before you start tor browser.