Overview

I often forget, so I'm taking notes. I'll add more if needed.

Environment

• ConoHa
• Ubuntu 18.04.2 LTS (Bionic Beaver)

Preparation

Install Ubuntu & Verify Root Login

Prepare an Ubuntu server on ConoHa and verify that you can log in as root.

Prepare SSH Keys on the Client Side

Create a private key and a public key.

ssh-keygen -t rsa ssh root@<ip address>

Setup

Server Update

Make sure to update.

sudo apt update && sudo apt upgrade -y

Create a User

Create a user with sudo privileges.

adduser <username> usermod -aG sudo <username>

Verify if the user belongs to the wheel group. groups <username>

※ Check the list of users cat /etc/passwd

Transfer the Public Key to the Server

Log in as the created user. su <username>

Prepare the .ssh directory. mkdir .ssh touch .ssh/authorized_keys chmod 700 .ssh chmod 600 .ssh/authorized_keys

Paste the public key created on the client side into ./ssh/authorized_keys.

Configure sshd_config and Open Ports

Change the SSH settings.

sudo vi /etc/ssh/sshd_config

Port 5005                                     // Change from default 22 to a custom number
PermitRootLogin no                    // Change from yes to no
PubkeyAuthentication yes         // Change from no to yes
PasswordAuthentication no      // Change from yes to no
UserPAM no                               // Change from yes to no

Restart SSH. sudo /etc/init.d/ssh restart

Continue to open ports.

sudo ufw allow 5005
sudo ufw allow 443
sudo ufw default deny    // Default setting might be deny...
sudo ufw enable

Check port settings. sudo ufw status

Verify SSH Connection

Edit the ~/.ssh/config file like this.

ServerAliveInterval 300
TCPKeepAlive yes
AddKeysToAgent yes
ForwardAgent yes
UseKeychain yes

Host conoha-demo
    Hostname    <ip address>
    User         <username>
    Port         5005   // The custom port number set above
    IdentityFile ~/.ssh/<pubkey name>

Verify SSH connection with ssh conoha-demo.

Thoughts

I feel like I wrote a similar note when I first touched CentOS.