Could not get lock /var/lib/dpkg/lock-frontend. It is held by process 4337 (unattended-upgr) code example

Example 1: Unable to acquire the dpkg frontend lock (/var/lib/dpkg/lock-frontend), is another process using it?

ps aux | grep -i dpkg

// Kill processes which are running
sudo kill -9 <pid>

// Restart the accounts daemon
sudo systemctl restart accounts-daemon

Example 2: E: Could not get lock /var/lib/dpkg/lock-frontend - open (11: Resource temporarily unavailable)

sudo rm /var/lib/apt/lists/locksudo rm /var/lib/apt/lists/lock-frontend