pelo terminal dá pra fazer isso com o comando:
su usuario firefox
espero que ajude
Fala Felix!
Bom, fiz o que me disse, mas não deu certo, apareceu a seguinte mensagem:
"No protocol specified
ERROR: X: Can't open display ":0.0".
Either the connection was refused and you do not have enough
access rights to connect to your X server or there is
something wrong with the contents of your DISPLAY variable.
If the connection was refused then please consult your system
administator or read the X documentation for a solution
(use xauth, xhost, or ssh -X)."
O que será?