lsof /var/lib/dpkg/lock-frontend code example

Example 1: dpkg: error: dpkg frontend lock was locked by another process with pid 4368

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

Example 2: E: Unable to acquire the dpkg frontend lock (/var/lib/dpkg/lock-frontend), are you root?

ps aux | grep -i apt