Set up password-less ssh in 5 minutes

I do this freaking a lot of times, and I sometimes forget about the process, so just to remind myself. It’s not only real easy, but also very secure. I highly recommend it. Technically it is called “SSH Key Exchange.” There might be a better person to talk about how it works, so I only explain how to set up.

Precondition

• Server has configured to accept PubkeyAuthentication
  Most likely, what a server admin need to do is comment-in 3 lines at /etc/ssh/sshd_config, and reboot ssh.
• You have generated a RSA key pair
  This is also very easy. Just type ssh-keygen -t rsa
• Use Mac OS X or Unix based system.
  I know windows people can do it with Putty. When I need to do it, I will write this again.

Procedure

1. login to where you want to connect to.
2. make a directory on $HOME on the server you want to connect to

   mkdir .ssh
   chmod 700 .ssh

3. copy public key from the client where you want to connect from. You can just open it with any text editor and get rid of line break.

   open $HOME/.ssh/id_rsa.pub

4. make a file on the server you want to connect to.

   cd $HOME/.ssh
   vi authorized_keys
   ...
   chmod 755 authorized_keys

5. try to connect

   ssh -i $HOME/.ssh/id_rsa -l USERNAME HOST_TO_CONNECT

That’s all! I often times, forgot to change permission… It matters!