Answers for "Could not open lock file /var/lib/dpkg/lock-frontend - open (13: Permission d enied) E: Unable to acquire the dpkg frontend lock (/var/lib/dpkg/lock-frontend), are y ou root?"

dpkg: error: dpkg frontend lock was locked by another process with pid 4368

sudo rm /var/lib/dpkg/lock-frontend
sudo dpkg --configure -a

E: Could not open lock file /var/lib/dpkg/lock-frontend - open (13: Permission denied) E: Unable to acquire the dpkg frontend lock (/var/lib/dpkg/lock-frontend), are you root?

sudo must be used before and after &&
Example:

sudo apt-get update && sudo apt-get upgrade