To generate ssh key/value pairs and add for login without password

ssh-keygen
will prompt to create public/private rsa key pair.we can use default(/home/<username>/.ssh/id_rsa) or custom location to save.And an optional passphrase to enter.
public: id_rsa.pub private:id_rsa

copy public key to other machine where we want to connect: steps

Then, we need to add on the remote machine, the user we are connecting with sudoers group.:steps

then, we can connect directly
ssh machine1

ssh server should be installed on the remote machine to have ssh connection : steps