Quick setup for ssh into ubuntu headless server and force use of a private key

1. Install openssh-server on ubuntu headless server
   • server$ sudo apt-get install openssh-server
2. Generate keypair
   • user@client:~$ ssh-keygen
     • (accepting all defaults places keys in ~/.ssh/* &&& uses default names of “id_rsa”, “id_rsa.pub” &&& uses RSA 2048 / SHA 256)
     • um… set a passphrase for the private key. fo’real
3. Send public key to server
   • user@client:~$ ssh-copy-id -i ~/.ssh/id_rsa.pub [server_name||ip_address]
4. (test via password) ssh from client to ubuntu headless server
   • user@client:~$ ssh admin@server
5. Disable ssh via passwords
   • admin@server:~$ sudo vi /etc/ssh/sshd_config
     • from: #PasswordAuthentication yes
     • to: PasswordAuthentication no
   • (test via password) ssh from client to ubuntu headless server
     • user@client:~$ ssh admin@server
     • if this fails with “Permission denied (publickey).” you are winning
6. (test via private key) ssh from client to ubuntu headless server
   • user@client:~$ ssh -i ~/.ssh/id_rsa admin@server