docker-commands

e) in jenkins UI portal:
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open jenkins dashboard > manage jenkins > manage plugins > install the following plugins 
"Docker", "Docker API"   "Docker Pipeline"   ""        , "Docker build steps", "CloudBees Docker Build and Publish plugin" and "Docker Commons Plugin"


b)In jenkins machine, run the below Install Docker engine <https://docs.docker.com/engine/install/ubuntu/>:
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sudo apt-get update

sudo apt-get install \
    apt-transport-https \
    ca-certificates \
    curl \
    gnupg-agent \
    software-properties-common

curl -fsSL https://download.docker.com/linux/ubuntu/gpg | sudo apt-key add -

sudo apt-key fingerprint 0EBFCD88

add-apt-repository \
   "deb [arch=amd64] https://download.docker.com/linux/ubuntu \
   $(lsb_release -cs) \
   stable"

sudo apt-get update

sudo apt-get install docker-ce docker-ce-cli containerd.io

sudo docker run hello-world



c) In jenkins machine, Manage Docker as a non-root user:
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sudo groupadd docker	                // Add the docker group if it doesn't already exist
sudo gpasswd -a jenkins docker     	// Add the connected user jenkins to the docker group.
newgrp docker
docker run hello-world	                // to check if you can run docker without sudo
systemctl restart docker	        // restart the docker daemon to get things working
sudo chmod 666 /var/run/docker.sock	// that is the key



d) supporting commands to manage jenkins user:
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getent passwd	                       // To get a list of all Linux user
less /etc/passwd	               // Get a List of All Users using the /etc/passwd File
getent passwd | grep jenkins	       // list details of specific user ex: jenkins
sudo passwd jenkins	               // set the password for user jenkins


e) stop asking the password for sudo:
-------------------------------------
sudo visudo                            // run this command
jenkins ALL=(ALL) NOPASSWD: ALL        // at the end of the file add this line then click ctrl+x