OpenSSH : Password Authentication2023/02/20

	Configure SSH Server to operate servers from remote computers.
[1]	OpenSSH is already installed by default even if you installed AlmaLinux with [Minimal] Install, so it does not need to install new packages. You can login with Password Authentication by default. If you like to improve the security, you should change PermitRootLogin parameter.

[root@dlp ~]#

vi /etc/ssh/sshd_config

# line 40: change ( prohibit root login )
# for other options, there are [prohibit-password], [forced-commands-only]

PermitRootLogin

[root@dlp ~]#

systemctl restart sshd

[2]	If Firewalld is running, allow SSH service. SSH uses [22/TCP].

[root@dlp ~]#

firewall-cmd --add-service=ssh

success
[root@dlp ~]#

firewall-cmd --runtime-to-permanent

success

SSH Client : AlmaLinux

	Configure SSH Client for AlmaLinux.
[3]	Install SSH Client.

[root@node01 ~]#

dnf -y install openssh-clients

[4]	Connect to SSH server with any common user.

# ssh [username@(hostname or IP address)]

[alma@node01 ~]$

ssh alma@dlp.srv.world

The authenticity of host 'dlp.srv.world (10.0.0.30)' can't be established.
ED25519 key fingerprint is SHA256:HpNlL+G8ceaugq5hFtzPJMDIu6MSSzGIwM4CxyhNDuw.
This key is not known by any other names
Are you sure you want to continue connecting (yes/no/[fingerprint])? yes
Warning: Permanently added 'dlp.srv.world' (ED25519) to the list of known hosts.
alma@dlp.srv.world's password:
[alma@dlp ~]$   # logined

[5]	It's possbile to execute commands on remote Host with SSH like follows.

# for example, run [cat /etc/passwd]

[alma@node01 ~]$

ssh alma@dlp.srv.world "cat /etc/passwd"

alma@dlp.srv.world's password:
root:x:0:0:root:/root:/bin/bash
bin:x:1:1:bin:/bin:/sbin/nologin
daemon:x:2:2:daemon:/sbin:/sbin/nologin
adm:x:3:4:adm:/var/adm:/sbin/nologin
lp:x:4:7:lp:/var/spool/lpd:/sbin/nologin
.....
.....
systemd-oom:x:984:984:systemd Userspace OOM Killer:/:/usr/sbin/nologin
systemd-resolve:x:983:983:systemd Resolver:/:/usr/sbin/nologin
alma:x:1000:1000::/home/alma:/bin/bash

SSH Client : Windows #1

	Configure SSH Client for Windows.
[6]	Download a SSH Client software for Windows. On this example, it uses Putty (www.chiark.greenend.org.uk/~sgtatham/putty/). Install and start Putty, then Input your server's Hostname or IP address on [Host name] field and Click [Open] button to connect.

[7]	After successing authentication, it's possible to login and operate AlmaLinux server from remote computer.

SSH Client : Windows #2

[8]	If you are using Windows 11, OpenSSH Client has been implemented as a Windows feature, so it's possible to use [ssh] command on PowerShell or Command Prompt without Putty or other 3rd party SSH softwares.

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