Lesson 1.4: Access remote systems using SSH

 
[root@client bin]# dnf install openssh-server
[root@client bin]# dnf install -y openssh-clients
[root@client bin]# systemctl enable --now sshd
[root@client bin]# systemctl status sshd

output

 
● sshd.service - OpenSSH server daemon
     Loaded: loaded (/usr/lib/systemd/system/sshd.service; enabled; preset: enabled)
     Active: active (running) since Sat 2024-04-06 08:47:20 +0545; 28s ago
       Docs: man:sshd(8)
             man:sshd_config(5)
   Main PID: 11214 (sshd)
      Tasks: 1 (limit: 22585)
     Memory: 1.3M
        CPU: 6ms
     CGroup: /system.slice/sshd.service
             └─11214 "sshd: /usr/sbin/sshd -D [listener] 0 of 10-100 startups"

Machine 1 - Server Configutation

 
[sanjeeb@server ~]$ hostname
server
[sanjeeb@server ~]$ hostname -I 
192.168.208.120

Machine 2 - Client Configutation

 
[sanjeeb@client ~]$ hostname
client
[sanjeeb@client ~]$ hostname -I 
192.168.208.130

Machine 1 --> Machine 2

 
[sanjeeb@server ~]$ ssh sanjeeb@192.168.208.130
The authenticity of host '192.168.208.130 (192.168.208.130)' can't be established.
ED25519 key fingerprint is SHA256:HOPA4UyrPYpCEWcP4vMfeocqZn9r5fEBYgg9+lXNyeY.
This host key is known by the following other names/addresses:
    ~/.ssh/known_hosts:1: 192.168.208.136
Are you sure you want to continue connecting (yes/no/[fingerprint])? yes
Warning: Permanently added '192.168.208.130' (ED25519) to the list of known hosts.
sanjeeb@192.168.208.130's password: 
Last login: Fri Apr  5 17:58:46 2024

Machine 1 - Generating SSH Key & Copying it to Machine 2

 
[sanjeeb@server ~]$ ssh-keygen
Generating public/private rsa key pair.
Enter file in which to save the key (/home/sanjeeb/.ssh/id_rsa): 
/home/sanjeeb/.ssh/id_rsa already exists.
Overwrite (y/n)? y
Enter passphrase (empty for no passphrase): 
Enter same passphrase again: 
Your identification has been saved in /home/sanjeeb/.ssh/id_rsa
Your public key has been saved in /home/sanjeeb/.ssh/id_rsa.pub
The key fingerprint is:
SHA256:e6+iQ8yUsMAvLRZvimHqzhngCNdgdKJSM/FtA6tW5I8 sanjeeb@server
The key's randomart image is:
+---[RSA 3072]----+
| .B.+            |
| ++O.+           |
|o o*=o+.         |
|oo+=*+o.         |
|=++=E+. S        |
|Bo.   +  .       |
|oo   .  . .      |
|..o   . .. .     |
|.+    .o ....    |
+----[SHA256]-----+

 
[sanjeeb@server ~]$ ssh-copy-id sanjeeb@192.168.208.130
/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
sanjeeb@192.168.208.130's password: 
 
Number of key(s) added: 1
 
Now try logging into the machine, with:   "ssh 'sanjeeb@192.168.208.130'"
and check to make sure that only the key(s) you wanted were added.

Machine 2 - Accessing Machine 1 from Machine 2 without Password Prompt

This shows that the authorized_keys.

 
[sanjeeb@client .ssh]$ pwd
/home/sanjeeb/.ssh
[sanjeeb@client .ssh]$ cat authorized_keys 
ssh-rsa AAAAB.......91YUs= sanjeeb@server

Now Machine 2 will not require the password of the Machine 1 user when connecting from Machine 1 to Machine 2.

 
[sanjeeb@server ~]$ ssh sanjeeb@192.168.208.130
Last login: Sat Apr  6 10:01:05 2024 from 192.168.208.120