I use Tor Browser in Ubuntu. I want to learn a way if possible to make the Tor Browser take the same identity each time I open it. Is it possible?
I interpret your use of the phrase "take the same identity" to mean that you want to have the same IP address (of your exit node) as in a past Tor session. In that case, the answer to your question is "Yes, but only indirectly".
Locate and edit your "torrc" file.
Add one new line to it, that says:
In the place of
SomeExitNodeName include the Name of the exit node that is at the IP address that you want to 'be'. Then stop Tor and restart it.
You can lookup the ExitNode name at http://torstatus.blutmagie.de/
If you cannot find the IP address you desire on that page then the party who previously hosted an exit node on that IP address is no longer doing that, so in that case you're out of luck.
pabouk is correct, I made mistake when I read question.
always the same identity is related to exit node, so, you can choose exit node in your torrc file. just find IP address you want (for example like below) and write:
ExitNodes 10.100.234.333 StrictNodes 1
in that way you will always get the same exit node, if you don't write strictnodes 1, tor can override your torrc parameters. theoretically if you pay some server anonymously with bitcoins and you make tor exit node, you can always use it for yourself, just add mentioned changes in your torrc file.
why he would do it is not valid question. for example I don't believe 100% to tor bridges and would make my own private bridge to connect to tor nodes.
so, my answer: I am not professional, but I think you can make your own obfuscate bridge and use it to connect to tor network. I suppose you would have to rent vps if not dedicated server, install obfuscate bridge and configure it to refuse to send information to tor developers so it will not be listed and known anywhere, then use at your PC: Pluggable Transports Tor Browser Bundle (https://www.torproject.org/docs/pluggable-transports.html.en). you can try to include only one obfs bridge, your one. I never tried, you can try it. bridges are written in torrc-defaults file.