sudo /usr/bin/sudo must be owned by uid 0 and have the setuid bit set
Got stuck by this error in Ubuntu 14.4 which is really painful as without sudo you cannot move forward … it will not allow you to do anything.
Solution:- Get in to Ubuntu Recovery Console
Start your computer and press and hold SHIFT key while booting. It will take you to the grub loader page as shown in image – 1.
Select and enter Advanced options for Ubuntu and from there select the kernel named as recovery mode as shown in image – 2.
select root – drop to root shell prompt as shown in image – 3
Now the file system is read only to Remount to Read Write run below command
# mount -o remount,rw /
# mount –all
then need to change the ownership for sudo
# chown root:root /usr/bin/sudo
give permisson for sudo
# chmod 4755 /usr/bin/sudo
it’s done … let’s see by restarting the machine
# shutdown -r now
Hopefully now you have solved the issue and sudo is working fine …