= Permission denied (publickey)
Mengutip dari salah satu [[https://askubuntu.com/a/16665 | jawaban]] di AskUbuntu, SSH sangat pilih-pilih terhadap permisi folder `.ssh` dan file `authorized_keys`.
```
sudo chown -R username:username /home/username/.ssh
sudo chmod 0700 /home/username/.ssh
sudo chmod 0600 /home/username/.ssh/authorized_keys
```
= Menyalin kunci ke peladen
Dari manual ssh-copy-id:

```
NAME
       ssh-copy-id — use locally available keys to authorise logins on a remote machine

SYNOPSIS
       ssh-copy-id [-f] [-n] [-s] [-i [identity_file]] [-p port] [-o ssh_option] [user@]hostname
       ssh-copy-id -h | -?

DESCRIPTION
       ssh-copy-id  is  a  script that uses ssh(1) to log into a remote machine (presumably using a login password, so password authentication should be enabled, unless you've done some
       clever use of multiple identities).  It assembles a list of one or more fingerprints (as described below) and tries to log in with each key, to see if any of them are already in‐
       stalled (of course, if you are not using ssh-agent(1) this may result in you being repeatedly prompted for pass-phrases).  It then assembles a list of those that  failed  to  log
       in,  and  using ssh, enables logins with those keys on the remote server.  By default it adds the keys by appending them to the remote user's ~/.ssh/authorized_keys (creating the
       file, and directory, if necessary).  It is also capable of detecting if the remote system is a NetScreen, and using its ‘set ssh pka-dsa key ...’ command instead.
```

Skrip ini menginstal kunci SSH pada server sebagai kunci resmi. Tujuannya adalah untuk menyediakan akses tanpa memerlukan kata sandi untuk setiap login. Hal ini memfasilitasi login otomatis tanpa kata sandi dan sistem masuk tunggal menggunakan protokol SSH.

```
ssh-copy-id -i ~/.ssh/mykey user@host
```

= SSH Tunnel
Secure Shell (SSH) Tunnel terdiri dari sebuah "terowongan" terenkripsi yang dibuat melalui koneksi protokol SSH. Pengguna dapat mengatur terowongan SSH untuk mentransfer lalu lintas yang tidak dienkripsi melalui jaringan melalui saluran terenkripsi.
```
ssh -N -L 8080:127.0.0.1:destinationport username@hostname
```