I think I already have all the things I can have except the root in this box.
I got two users, I find the two groups that my R user belongs too.
One group with many ppl, one group only have R.
After I read all the hints, I still have no idea about the next step.
Tried to google with the Win version, with the groups and the privilege of R, no luck.
At this moment, I see no hope to get it through.