How do I setup Public-Key Authentication?

Question

How do I setup Public-Key Authentication for SSH?

Answer 1

This is good tutorial on how to setup Public-Key Authentication.

http://sial.org/howto/openssh/publickey-auth/

Answer 2

For windows this is a good introduction and guide

Here are some good ssh-agents for systems other than linux.

• Windows - pageant
• OS X - SSHKeychain

Answer 3

If you have SSH installed, you should be able to run..

ssh-keygen

Then go through the steps, you'll have two files, idrsa and idrsa.pub (the first is your private key, the second is your public key - the one you copy to remote machines)

Then, connect to the remote machine you want to login to, to the file ~/.ssh/authorized_keys add the contents of your that id_rsa.pub file.

Oh, and chmod 600 all the id_rsa* files (both locally and remote), so no other users can read them.

Then, when you do ssh remote.machine, it should ask you for the key's password, not the remote machine.

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To make it nicer to use, you can use ssh-agent to hold the decrypted keys in memory - this means you don't have to type your keypair's password every single time. To launch the agent, you run

`ssh-agent`

On some distros, ssh-agent is started automatically. If you run echo $SSH_AUTH_SOCK and it shows a path (probably in /tmp/) it's already setup, so you can skip the previous command.

Then to add your key, you do

ssh-add ~/.ssh/id_rsa

and enter your passphrase. It's stored until you remove it (using the ssh-add -D command, which removes all keys from the agent)

Answer 4

@dbr in Linux/Unix, you'll probably need to chmod 600 the .ssh directory as well. ssh is very fussy about these things :-)