I am trying to prevent the guest user from accessing software-center (I know it can't install anything, but I don't even want it to browse) The file is owned by root and in group root. I run: sudo chmod o= /usr/bin/software-center Afterwards I run ls -l and get the following output: lrwxrwxrwx 1 root root 40 Sep 10 14:28 /usr/bin/software-center -> ../share software- center/software-center The first part of the output indicates chmod didn't do anything and the second part I don't understand.