How to set up password less SSH in linux ?

Source: Node1 (10.20.30.1)

Target: Node2 (10.20.30.2)

From Node1 we will setup passwordless SSH to Node2 and vice verse.

1- Login to Node1 as the same user on which the password less SSH is required .

Here we are using root user .

2-Now run the ssh keygen

[root@node1 ]# ssh-keygen -t rsa

Generating public/private rsa key pair.

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

Enter passphrase (empty for no passphrase):

Enter same passphrase again:

Your identification has been saved in /root/.ssh/id_rsa.

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

The key fingerprint is:

SHA256:qYu/TJOvB44ewNd4UU3A/kmMG1bhAJRIqnjinl9C2Cw root@node1

The key's randomart image is:

+---[RSA 2048]----+

| .o+...oo |

| .. ..... |

| .. .o . |

| . o o.o. + o |

| o o = So . O |

| o B.= o + . |

| Eo@.. |

| .B.B. |

| .ooX+. |

+----[SHA256]-----+

3-Now we will use the ssh-copy-id to installs the SSH key on target server as an authorized key. Its purpose is to provide access without requiring a password for each login

[root@node1 ]# ssh-copy-id root@10.20.30.2

/usr/bin/ssh-copy-id: INFO: Source of key(s) to be installed: "/root/.ssh/id_rsa.pub"

/usr/bin/ssh-copy-id: INFO: attempting to log in with the new key(s), to filter out any that are already installed

/usr/bin/ssh-copy-id: INFO: 1 key(s) remain to be installed -- if you are prompted now it is to install the new keys

root@10.20.30.2's password:

Number of key(s) added: 1

Now try logging into the machine, with: "ssh 'root@10.20.30.2'"

and check to make sure that only the key(s) you wanted were added.

4-As mentioned above now we will try to ssh the target server to check the password less ssh is working or not .

[root@node1 ]# ssh root@10.20.30.2

Last login: Wed Aug 30 18:44:41 2023 from 10.20.30.1

[root@node2 ~]# exit