I am using debian 7.0 and I added "debian-transmission" to the group "pi" with:
usermod -a -G pi debian-transmission
I made this change because transmission was not able to write the pi mounted hdd. Later I realised that pi is also belongs to sudo. My question is: does debian-transmission belong also to sudo supplementary group just because became to member of pi group which belongs to sudo, or with the above mentioned command I put only the member of pi group?