SSH (Secure Shell) [IlyasaWiki]

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====== SSH (Secure Shell) ======

SSH (Secure Shell) adalah protokol jaringan yang digunakan untuk komunikasi aman antar komputer.  
Semua data yang dikirim melalui SSH dienkripsi sehingga terlindungi dari penyadapan maupun serangan.  
SSH banyak dipakai untuk:

  * Mengelola server jarak jauh
  * Transfer file dengan aman
  * Membuat koneksi terenkripsi di jaringan publik

----

===== Instalasi SSH Server (Ubuntu/Debian) =====

<code bash>
sudo apt update
sudo apt install openssh-server
</code>

=== Mengecek status service ===
<code bash>
systemctl status ssh
</code>

Output normalnya akan menunjukkan service **active (running)**.  

=== Lokasi file konfigurasi utama ===
<code>
/etc/ssh/sshd_config
/etc/ssh/sshd_config.d/
</code>

----

===== Menggunakan SSH =====

=== Koneksi ke server ===
<code bash>
# Default port (22)
ssh user@192.168.1.5

# Dengan port tertentu
ssh user@192.168.1.5 -p 6222
</code>

=== Menjalankan perintah langsung ===
<code bash>
# Menjalankan perintah di server
ssh user@192.168.1.5 'ls -l'

# Menjalankan script lokal di server
ssh user@192.168.1.5 bash < script.sh

# Kompres dan unduh file/folder dari server
ssh user@192.168.1.5 "tar czf - ~/source" > output.tgz
</code>

----

===== Transfer File dengan SCP =====
<code bash>
# Copy dari remote ke local
scp user@server:/dir/file.ext ./dest/

# Copy dari local ke remote
scp ./file.ext user@server:/dir/

# Copy folder (rekursif)
scp -r user@server:/dir ./dest/

# Copy antar remote server
scp user@server1:/file user@server2:/dir

# Copy semua isi folder
scp user@server:/dir/* ./
</code>

----

===== SSH Key =====

SSH Key memudahkan login tanpa password dengan sistem **public/private key**.

=== Membuat SSH Key ===
<code bash>
# RSA 4096 bit
ssh-keygen -t rsa -b 4096 -C "your@mail.com"

# Ed25519 (lebih modern & ringan)
ssh-keygen -t ed25519 -C "comment's key"

# Interaktif default
ssh-keygen

# Tentukan nama file key
ssh-keygen -f ~/.ssh/custom_key
</code>

=== Operasi tambahan ===
<code bash>
# Buat public key dari private key
ssh-keygen -y -f private.key > public.pub

# Ubah komentar key
ssh-keygen -c -f ~/.ssh/id_rsa

# Ubah passphrase private key
ssh-keygen -p -f ~/.ssh/id_rsa
</code>

=== Menyalin key ke server ===
<code bash>
ssh-copy-id user@server

# Menyalin key tertentu
ssh-copy-id -i ~/.ssh/id_rsa.pub user@server
</code>

==== Jenis Key ====
  * rsa
  * ed25519
  * dsa (lama, jarang dipakai)
  * ecdsa

==== Format Key ====
  * PEM
  * PKCS8

----

===== File Konfigurasi SSH =====

^ Path                        ^ Deskripsi                   |
| /etc/ssh/ssh_config         | Konfigurasi global (client) |
| ~/.ssh/config               | Konfigurasi user (client)   |
| ~/.ssh/id_{type}            | Private key                 |
| ~/.ssh/id_{type}.pub        | Public key                  |
| ~/.ssh/known_hosts          | Daftar host yang dikenal    |
| ~/.ssh/authorized_keys      | Public key yang diizinkan   |

----

===== Contoh Konfigurasi ~/.ssh/config =====

<code>
# Opsi global
ForwardAgent yes
ServerAliveInterval 60
Compression yes

# Host tertentu
Host example.com
    HostName example.com
    User username
    Port 22
    IdentityFile ~/.ssh/id_rsa
    # ProxyJump jump.example.com   # Gunakan bastion/jump host

# Alias untuk koneksi cepat
Host server1
    HostName 192.168.1.10
    User admin
    Port 2222
    IdentityFile ~/.ssh/id_ed25519
</code>

=== Menggunakan alias ===
<code bash>
ssh server1
</code>