Jun
23
2014

SSH Public Key Auth

PublicKey Authentication SSH

PublicKey Authentication SSH

If you frequently access hosts using ssh with user and password and do not know public key authentication, this post is for you.

I will not explain about advantages and disadvantages, clearly and practically I want to show you how create and use the private key to authenticate on ssh.

To create a public key and a private key we use the command ssh-keygen

$ ssh-keygen -t dsa

Type enter until create the keys, that will stay at .ssh in your home

$ ls -l ~/.ssh
/home/your_username/.ssh/id_dsa
/home/your_username/.ssh/id_dsa.pub

Now you need copy the content of public key to autorized_key file at the .ssh directory of your remote server.
There are many ways to do it, the simplest may be the following.

$ ssh remote_user@remote_host "echo `cat ~/.ssh/id_dsa.pub` >> ~/.ssh/authorized_keys"

In one line, this command connect to remote host and copy the public key to correct file. Probably you need to type the remote user’s password to login.

Replace remote_user to user that should login in remote host and, logically replace remote_host to server that you want to login.

May occur that the .ssh does not exists in the remote server at the home user directory, to solve it I run the command to create directory if do not exists.

$ ssh remote_user@remote_host mkdir -p .ssh

It is important to stress that the server should be configured to accept public key authentication, where is configured in the file /etc/ssh/sshd_config

# allow public key authentication
PubkeyAuthentication yes

If necessary to reconfigure the server, you need restart the service:
For CentOS

$ svc -du /var/service/sshd/

Plus!

I created a script that does everything at once. You only need to replace the variables that I mentioned above (user and host) and then the script is ready:

I hope this helps.

Written by Luis com S in: Quick Posts |

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