debian apt-get install net-tools permission denied frontend lock root code example

Example 1: Could not open lock file /var/lib/dpkg/lock-frontend - open (13: Permission denied)

Try 'sudo apt-get update' or 'sudo apt-get upgrade'

Example 2: 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