新Linux入門｜sshコマンドで安全にリモート接続する：ホスト認証と公開鍵認証の仕組み

[suzuki@AlmaLinux ~]$ ssh tanaka@192.168.0.10

ssh [オプション] [ユーザー名@]接続先ホスト名（またはIPアドレス）

[suzuki@AlmaLinux ~]$ ssh tanaka@10.0.2.15
The authenticity of host '10.0.2.15 (10.0.2.15)' can't be established.
ED25519 key fingerprint is SHA256:N3+a6TS/PmMLOm3mCnCSvDio06LM3vQyEWyRrkmpd0I.
This key is not known by any other names
Are you sure you want to continue connecting (yes/no/[fingerprint])? yes
Warning: Permanently added '10.0.2.15' (ED25519) to the list of known hosts.
tanaka@10.0.2.15's password: 
Last login: Sun Dec  7 22:55:41 2025
[tanaka@AlmaLinux ~]$ exit
ログアウト
Connection to 10.0.2.15 closed.
[suzuki@AlmaLinux ~]$ 

[suzuki@AlmaLinux ~]$ su - tanaka
パスワード:
[tanaka@AlmaLinux ~]$ ssh-keygen -t rsa
Generating public/private rsa key pair.
Enter file in which to save the key (/home/tanaka/.ssh/id_rsa): 
Created directory '/home/tanaka/.ssh'.
Enter passphrase (empty for no passphrase): # パスフレーズの入力
Enter same passphrase again:                # 再度パスフレーズの入力
Your identification has been saved in /home/tanaka/.ssh/id_rsa
Your public key has been saved in /home/tanaka/.ssh/id_rsa.pub
The key fingerprint is:
SHA256:qw4++oa1cYWEE4uve9I38p3euxFOZuO/UWeOv56xzvs tanaka@AlmaLinux
The key's randomart image is:
+---[RSA 3072]----+
|    .o           |
|   .o..          |
|  . .o .         |
|   .  . .        |
|    .  .S *   . o|
|   .o .  B o . = |
|  .+.+  . + . ...|
|  ooB.oo o o ...+|
|  o*o*+o+ +oo.oOE|
+----[SHA256]-----+

[tanaka@AlmaLinux ~]$ ssh-copy-id tanaka@10.0.2.15
/usr/bin/ssh-copy-id: INFO: Source of key(s) to be installed: "/home/tanaka/.ssh/id_rsa.pub"
The authenticity of host '10.0.2.15 (10.0.2.15)' can't be established.
ED25519 key fingerprint is SHA256:N3+a6TS/PmMLOm3mCnCSvDio06LM3vQyEWyRrkmpd0I.
This key is not known by any other names
Are you sure you want to continue connecting (yes/no/[fingerprint])? yes
/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
tanaka@10.0.2.15's password: # パスワードの入力

Number of key(s) added: 1

Now try logging into the machine, with:   "ssh 'tanaka@10.0.2.15'"
and check to make sure that only the key(s) you wanted were added.

[tanaka@AlmaLinux ~]$ ssh tanaka@10.0.2.15
Enter passphrase for key '/home/tanaka/.ssh/id_rsa': # パスフレーズの入力
Last login: Mon Dec  8 01:08:58 2025 from 10.0.2.15
[tanaka@AlmaLinux ~]$ 

[tanaka@AlmaLinux ~]$ exit
ログアウト
Connection to 10.0.2.15 closed.
[tanaka@AlmaLinux ~]$