[UBUNTU] Fixed Error E: Could not get lock /var/lib/dpkg/lock-frontend. It is held by process xxxx (unattended-upgr)

When I ran a command sudo apt-get upgrade (apt upgrade) or sudo apt-get install (apt install ). I receive an error

ubuntu@NUC-DEV:~$ sudo apt-get upgrade
E: Could not get lock /var/lib/dpkg/lock-frontend. It is held by process 6146 (unattended-upgr)
N: Be aware that removing the lock file is not a solution and may break your system.
E: Unable to acquire the dpkg frontend lock (/var/lib/dpkg/lock-frontend), is another process using it?

Solution

• Check which process lock file /var/lib/dpkg/lock-frontend by command

sudo lsof /var/lib/dpkg/lock

• Set Process ID (PID) -- Sample is 6750

COMMAND    PID USER   FD   TYPE DEVICE SIZE/OFF     NODE NAME
unattende 6750 root   11uW  REG    8,2        0 21501278 /var/lib/dpkg/lock

• Kill PID, who hold lock file

sudo kill -9 6750

• Delete and Clear Cache

#Clear Lock File
sudo rm /var/lib/dpkg/lock
sudo rm /var/lib/dpkg/lock-frontend
sudo rm /var/lib/apt/lists/lock
#Clear Cache
sudo rm /var/cache/apt/archives/lock

• reconfig state

sudo dpkg --configure -a

• Test sudo apt-get upgrade again.