Using chmod for /usr directory

I used the following command to change the permissions of the usr directory from root

root> chmod -R 777 /usr

Now when I try to use the sudo command it gives the following error: sudo: must be setuid root

On googling, I found that this error happens if /usr is chowned and I need to reinstall Ubuntu. But am I getting this error for chmod? Is there anyw开发者_JAVA百科ay to fix this problem without reinstalling?

To setuid /usr/bin/sudo: chmod +s /usr/bin/sudo.

But you changed ALL file/directory attributes in /usr recursivly (-R). You really should try some rescue mode. I don't think you'll have any chance to repair it.