ssh-password-less-login-with-dsa-publickey-authentication

Q. How do you set-up SSH with DSA public key authentication? I have Linux laptop called tom and remote Linux server called jerry. How do I setup DSA based authentication so I don’t have to type password?

A. DSA public key authentication can only be established on a per system / user basis only i.e. it is not system wide. You will be setting up ssh with DSA public key authentication for SSH version 2 on two machines:

#1 machine : your laptop called tom
#2 machine : your remote server called jerry

Command to type on your laptop/desktop (local computer)

First login to local computer called tom and type the following command.

Step #1: Generate DSA Key Pair

Use ssh-keygen command as follows:
$ ssh-keygen -t dsa
Output:

Enter file in which to save the key (/home/vivek/.ssh/id_dsa):  Press [Enter] key

Enter passphrase (empty for no passphrase):

Enter same passphrase again:

Your identification has been saved in /home/vivek/.ssh/id_dsa.

Your public key has been saved in /home/vivek/.ssh/id_dsa.pub.

The key fingerprint is:

04:be:15:ca:1d:0a:1e:e2:a7:e5:de:98:4f:b1:a6:01 vivek@vivek-desktop

Caution: a) Please don’t enter any passphrase or enter a passphrase different from your account password and confirm the same.
b) The public key is written to /home/you/.ssh/id_dsa.pub.
c) The private key is written to /home/you/.ssh/id_dsa.
d) It is important you never-ever give out your private key.

Step #2: Set directory permission

Next make sure you have correct permission on .ssh directory:
$ cd
$ chmod 755 .ssh

Step #3: Copy public key

Now copy file ~/.ssh/id_dsa.pub on Machine #1 (tom) to remote server jerry as ~/.ssh/authorized_keys:
$ scp ~/.ssh/id_dsa.pub user@jerry:.ssh/authorized_keys

Command to type on your remote server called jerry

Login to your remote server and make sure permissions are set correct:
$ chmod 600 ~/.ssh/authorized_keys

Task: How do I login from client to server with DSA key?

Use scp or ssh as follows from your local computer:
$ ssh user@jerry
$ ssh user@remote-server.com
$ scp file user@jerry:/tmp