Waiting for cache lock: Could not get lock /var/lib/dpkg/lock-frontend. It is held by proc 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: 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 3: E: Could not get lock /var/lib/dpkg/lock-frontend - open (11: Resource temporarily unavailable) E: Unable to acquire the dpkg frontend lock (/var/lib/dpkg/lock-frontend), is another process using it?

ps aux | grep -i apt

sudo kill <process_id>
# Check if the process was killed by running the ‘ps aux | grep -i apt’ command. If it is still running, force kill it with SIGKILL signal:

sudo kill -9 <process_id>
# Another, easier way would be to use the killall command. This will kill all the instances of a running program:

sudo killall apt apt-get