BusyBox v1.19.3 (Debian 1.19.3power3) built-in shell (ash)
Enter 'help' for a list of built-in commands.

~ $ root
sudo: must be setuid root
~ $ ls -l /usr/bin/sudo
-rwxr-xr-x 2 root root 90040 Apr 17 2009 /usr/bin/sudo
~ $ chown root:root /usr/bin/sudo
chown: /usr/bin/sudo: Operation not permitted
~ $ chmod 4755 /usr/bin/sudo
chmod: /usr/bin/sudo: Operation not permitted
~ $ reboot
-sh: reboot: not found