ssh-passwordless

Sometimes we need a ssh connection that do not ask for passwords. It is use frequently in scripts that involve ssh, scp or sftp connections. Steps to make such connection:

1. Login as user1 on computer1 and generate a pair of authentication keys. Note: even if is unsecured to work without password, do not enter it. Let it empty...

[user1@computer1]$ ssh-keygen -t rsa 

Generating public/private rsa key pair. 

Enter file in which to save the key (/home/user1/.ssh/id_rsa): 

Created directory '/home/user1/.ssh'. 

Enter passphrase (empty for no passphrase): 

Enter same passphrase again: 

Your identification has been saved in /home/user1/.ssh/id_rsa. 

Your public key has been saved in /home/user1/.ssh/id_rsa.pub. 

The key fingerprint is: 31:df:a5:73:4a:2f:a6:6c:1c:32:a2:f2:b3:c5:a7:1f user1@computer1

2. Login to the remote computer (computer2) as user2 and create the .ssh directory (many Linux distributions create this folder by default). You still need the password for now.

[user1@computer1]$ ssh user2@computer2 mkdir -p .ssh 

user2@computer2's password:

3. Copy the user1 public key to user2@computer2 .ssh folder into authorized_keys [or authorized_keys2] file. And, type the password again for the last time.

[user1@computer1]$ cat .ssh/id_rsa.pub | ssh user2@computer2 > 'cat >> .ssh/authorized_keys' 

user2@computer2's password:

4. If all things are OK, you don't need the password:

[user1@computer1]$ ssh user2@computer2 

[user2@computer2]$

Or optionaly:

[user1@computer1]$ ssh -i $HOME/.ssh/id_rsa user2@computer2