ssh using authorized_keys

You can use this guide to connect via ssh to Linux machines without using a password, but instead use an authorized public/private key pair.

1. Follow these steps to generate a ssh-key with ssh-keygen
   • Open a local terminal on your laptop and type

     ssh-keygen -t rsa -b 4096
     

   • Hit enter to each of the questions
   • No, you do not need a passphrase
2. Follow these steps to copy your public key
   • In the local terminal type

     cat .ssh/id_rsa.pub
     

   • This will print out your public key, select and copy it from the terminal
   • Make sure you copy the whole thing beginning with ssh-rsa ending with something like dbalash@m1-mcs-dbalash
3. Open a new terminal and login to a Linux machine via ssh.
   • In the local terminal type

     ssh username@machine.name
     

   • Enter your password when prompted. (Note: you will not see the password characters as you type them.)
   • If you see a message like this

     RSA key fingerprint is 96:a9:23:5c:cc:d1:0a:d4:70:22:93:e9:9e:1e:74:2f.
     Are you sure you want to continue connecting (yes/no)? yes
     

   • Type yes and hit return.
4. Change directory to the .ssh folder.
   • In the new Linux terminal type

      cd .ssh
     

   • Note, if the above command does not work because there is no .ssh folder then run the following command to make the directory.

      mkdir .ssh
      cd .ssh
     

5. Edit or create the file authorized_keys to add your newly created public key to the file.
   • In the Linux terminal type

      nano authorized_keys
     

   • Paste your public key into the file.
   • Save and exit nano, by typing Ctrl-X, the type Y (for yes), and hit enter to accept the file name to save to is authorized_keys.
6. Logout of the Linux machine.
   • In the Linux terminal type

      exit
     

7. On your personal laptop edit the .ssh/config file.
   • In the local terminal type

      nano .ssh/config
     

     Note: if you are on a Windows PC and nano is not installed, you can try notepad.exe like this notepad.exe .ssh/config

   • Add the following lines to the file

       Host kali
           HostName 44.201.224.29
           User username
           IdentityFile ~/.ssh/id_rsa
     

   • Replace username with your username. For example, dbalash for me.
   • Save and exit nano, by typing Ctrl-X, the type Y (for yes), and hit enter to accept the file name to save to is ./ssh/config.
8. Connect again Linux machine.
   • In a local terminal type

      ssh kali
     

9. Troubleshooting: if it did not work, you can try the following.
   • Open a terminal on your laptop type the following to start the ssh-agent

       eval "$(ssh-agent -s)"
     

   • then use the ssh-add command

       ssh-add .ssh/id_rsa