How to connect to remote linux machine with key without entering password

On workstation

Create public/private key pair.

Put private key in  .ssh/id_rsa. Assign permissions as below.

ssh-keygen -t rsa -b 4096

mkdir .ssh

mv yolo ../.ssh/id_rsa

cd ../.ssh

chmod 600 id_rsa

cd ../

chmod 700 .ssh

On server

You need to create directory .ssh on substitute

Creat file authorized_keys

Assign appropriate permissions on file and directory

chmod 700 .ssh

cd .ssh

nano authorized_keys

chmod 600 authorized_keys

Connection made in form ssh username@hostname

How to avoid prompting password for sudo

In file /etc/sudoers modify add row where 'username' are your username

# Allow members of group sudo to execute any command

%sudo   ALL=(ALL:ALL) ALL

username ALL=(ALL) NOPASSWD:ALL

One key can be used to connect to any number of hosts.