I tried running sudo
in a terminal and was greeted with the error message:
sudo: unknown uid 501: who are you?
I tried doing an ls -l ~
, and instead of seeing my user name in the file entries, I saw 501
.
I think this might have happened in the process of upgrading Mac OS to Sierra; at least I think this is the first time I tried to run sudo
since upgrading.
Best Answer
The problem was fixed by restarting the MacBook Pro.
However, when I first executed the restart, the system hung with a black screen. I then forced the power off (by keeping pressed the power button for several seconds), then turned it on. Then it worked.