OpenSSH : Password Authentication2025/08/11

	Configure SSH Server to manage a server from the remote computer. SSH uses 22/TCP.
[1]	Password Authentication for OpenSSH Server on Debian is enabled by default, so it's possible to login without changing any settings. Furthermore, root account is prohibited Password Authentication by default with [PermitRootLogin prohibit-password], so default setting is good for use. But if you prohibit root login all, change like follows.

root@dlp:~#

apt -y install openssh-server

root@dlp:~#

vi /etc/ssh/sshd_config

# line 33 : uncomment and change to [no]

PermitRootLogin

root@dlp:~#

systemctl restart ssh

SSH Client : Debian

	Configure SSH Client for Debian.
[2]	Install SSH Client.

root@client:~#

apt -y install openssh-client

[3]	Connect to the SSH server with a common user.

# ssh [username@hostname or IP address]

debian@client:~$

ssh debian@dlp.srv.world

The authenticity of host 'dlp.srv.world (10.0.0.30)' can't be established.
ED25519 key fingerprint is SHA256:CH6c2yxTWxqmciVV1P1uDl3jwqKYsJFL3Iwa/fc5wKw.
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.
debian@dlp.srv.world's password:
Linux dlp.srv.world 6.12.38+deb13-amd64 #1 SMP PREEMPT_DYNAMIC Debian 6.12.38-1 (2025-07-16) x86_64

The programs included with the Debian GNU/Linux system are free software;
the exact distribution terms for each program are described in the
individual files in /usr/share/doc/*/copyright.

Debian GNU/Linux comes with ABSOLUTELY NO WARRANTY, to the extent
permitted by applicable law.
debian@dlp:~$     # logined

[4]	It's possible to execute commands on remote Host with adding commands to ssh command.

# for example, open [/etc/passwd] on remote host

debian@client:~$

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

debian@dlp.srv.world's password:
root:x:0:0:root:/root:/bin/bash
daemon:x:1:1:daemon:/usr/sbin:/usr/sbin/nologin
bin:x:2:2:bin:/bin:/usr/sbin/nologin
sys:x:3:3:sys:/dev:/usr/sbin/nologin
sync:x:4:65534:sync:/bin:/bin/sync
games:x:5:60:games:/usr/games:/usr/sbin/nologin
man:x:6:12:man:/var/cache/man:/usr/sbin/nologin
.....
.....

SSH Client : Windows#1

	Configure SSH Client for Windows.
[5]	Get a SSH Client for Windows. This example shows to use Putty like follows. Input your server's IP address and Click [Open] button.

[6]	After authentication on SSH server, it's possible to login remotely with SSH.

SSH Client : Windows #2

[7]	OpenSSH Client has been implemented as an Windows feature, so it's possible to use ssh command on PowerShell or Command Prompt without Putty and other SSH software.

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