I have a vital problem because of my stupid fault. I've been learning file security on my main OS (Ubuntu 16.04). I changed my /usr directory's permissions by executing sudo chmod 750 /usr command. Now, I'm not able to execute any app and not able to use sudo command anymore. I had never back-up the system. Is it possible to recover this? Thanks in advance...How can I recover this with live USB?
Unable to use sudo and other apps
sudo;chmod
Boot in recovery-mode. There you are root. mount -o remount,rw / chmod 0755 /usr