Passwordless logins

A passwordless login is possible via ssh if you have established a trust relationship between two computers.

Goal

You want to log in using ssh to a computer. You do not want to enter a password, however it needs to be secured.

Solution

Establish a trust relationship so your desktop's ssh key is authorized on your server like this:

desktop:~ # ssh-keygen -t dsa
Generating public/private dsa key pair.
Enter file in which to save the key (/root/.ssh/id_dsa):
Enter passphrase (empty for no passphrase):
Enter same passphrase again:
Your identification has been saved in /root/.ssh/id_dsa.
Your public key has been saved in /root/.ssh/id_dsa.pub.
The key fingerprint is:
1c:9a:b8:03:ab:04:b3:7b:75:49:99:8c:51:79:5d:06 root@scorpio
desktop:~ # scp .ssh/id_dsa.pub root@server:~/.ssh/authorized_keys

In this example, you create a key pair with no passphrase and distribute the public key from the computer desktop to server. The user root from desktop no longer needs to authenticate with his password, he can log in to server from desktop with the command

desktop:~ # ssh server
Welcome to server.
server:~ #