Answers for "could not get lock /var/lib/dpkg/lock-frontend linux"

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

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

Method 1
ps aux | grep -i apt
sudo kill -9 <process_id>

Method 2

sudo lsof /var/lib/dpkg/lock
sudo lsof /var/lib/apt/lists/lock
sudo lsof /var/cache/apt/archives/lock

sudo kill -9 <process_id>

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

sudo dpkg --configure -a

sudo apt update

waiting for cache lock, Could not get lock /var/lib/dpkg/lock-frontend.

sudo lsof /var/lib/dpkg/lock
or 
sudo lsof /var/lib/apt/lists/lock
or
sudo lsof /var/lib/dpkg/lock-frontend

apt lock

rm -rf /var/cache/apt/* /var/lib/dpkg/lock /var/lib/dpkg/lock-frontend 
/var/cache/debconf/ /var/lib/apt/lists/* 
/var/lib/dpkg/lock /var/lib/dpkg/lock-frontend /var/cache/debconf/