su

I enter the su command, enter the password, and I get an error. And when sudo, everything is fine. What could be wrong? Distribution: ubuntu.

I entered some command and it "knocked down" the rights. I restored them, almost everything works, but I can't run the shell ... output: $ ls -l /bin/su -rwsr-xr-x 1 jashka jashka 41072 июля 15 2015 /bin/su $ su Пароль: setgid: Операция не позволена