Could not get lock /var/lib/dpkg/lock-frontend. It is held by process 5403 (unattended-upgr) code example

Example 1: 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

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

sudo rm /var/cache/apt/archives/lock
sudo rm /var/lib/dpkg/lock