Latest news from 5wire Networks

Introduction

This guide should cover everything needed for initial server setup with Ubuntu 18.04. When you first create a new Ubuntu 18.04 server, there are a few configuration steps that you should take early on as part of the basic setup. This will increase the security and usability of your server and will give you a solid foundation for subsequent actions.

Step 1 — Logging in as Root

To log into your server, you will need to know your server’s public IP address. You will also need the password or, if you installed an SSH key for authentication, the private key for the root user’s account.

If you are not already connected to your server, go ahead and log in as the root user using the following command (substitute [your_server_ip] your server’s public IP address):

ssh root@your_server_ip

Accept the warning about host authenticity if it appears. If you are using password authentication, provide your root password to log in and if you are using an SSH key that is passphrase protected, you may be prompted to enter the passphrase the first time you use the key each session. If this is your first time logging into the server with a password, you may also be prompted to change the root password.

About Root

The root user is the administrative user in a Linux environment that has very broad privileges. Because of the heightened privileges of the root account, you are discouraged from using it on a regular basis. This is because part of the power inherent with the root account is the ability to make very destructive changes, even by accident. So after initial server setup its use should be limited.

The next step is to set up an alternative user account with a reduced scope of influence for day-to-day work. We’ll teach you how to gain increased privileges during the times when you need them.

Step 2 — Creating a New User

Once you are logged in as root, we’re prepared to add the new user account that we will use to log in from now on.

This example creates a new user called sammy, but you should replace it with a username that you like:

adduser sammy

You will be asked a few questions, starting with the account password.

Enter a strong password and, optionally, fill in any of the additional information if you would like. This is not required and you can just hit [ENTER] in any field you wish to skip.

Step 3 — Granting Administrative Privileges

Now, we have a new user account with regular account privileges. However, we may sometimes need to do administrative tasks.

To avoid having to log out of our normal user and log back in as the root account, we can set up what is known as “superuser” or root privileges for our normal account. This will allow our normal user to run commands with administrative privileges by putting the word [sudo] before each command.

To add these privileges to our new user, we need to add the new user to the sudo group. By default, on Ubuntu 18.04, users who belong to the sudo group are allowed to use the [sudo] command.

As root, run this command to add your new user to the sudo group (substitute [sammy] with your new user):

usermod -aG sudo sammy

Now, when logged in as your regular user, you can type [sudo] before commands to perform actions with superuser privileges.

Step 4 — Setting Up a Basic Firewall

Ubuntu 18.04 servers can use the UFW firewall to make sure only connections to certain services are allowed. We can set up a basic firewall very easily using this application.

Different applications can register their profiles with UFW upon installation. These profiles allow UFW to manage these applications by name. OpenSSH, the service allowing us to connect to our server now, has a profile registered with UFW.

You can see this by typing:

ufw app list

Output
Available applications:
  OpenSSH

We need to make sure that the firewall allows SSH connections so that we can log back in next time. We can allow these connections by typing:

ufw allow OpenSSH

Afterwards, we can enable the firewall by typing:

ufw enable

Type “[y]” and press [ENTER] to proceed. You can see that SSH connections are still allowed by typing:

ufw status

Output
Status: active

To                         Action      From
--                         ------      ----
OpenSSH                    ALLOW       Anywhere
OpenSSH (v6)               ALLOW       Anywhere (v6)

As the firewall is currently blocking all connections except for SSH, if you install and configure additional services, you will need to adjust the firewall settings to allow acceptable traffic in. You can learn some common UFW operations in this guide from Digital Ocean.

Step 5 — Enabling External Access for Your Regular User

Now that we have a regular user for daily use, we need to make sure we can SSH into the account directly.

Note: Until verifying that you can log in and use [sudo] with your new user, we recommend staying logged in as root. This way, if you have problems, you can troubleshoot and make any necessary changes as root.

The process for configuring SSH access for your new user depends on whether your server’s root account uses a password or SSH keys for authentication.

If the Root Account Uses Password Authentication

If you logged in to your root account using a password, then password authentication is enabled for SSH. You can SSH to your new user account by opening up a new terminal session and using SSH with your new username:

ssh sammy@your_server_ip

After entering your regular user’s password, you will be logged in. Remember, if you need to run a command with administrative privileges, type [sudo] before it like this:

sudo command_to_run

You will be prompted for your regular user password when using [sudo] for the first time each session (and periodically afterwards).

To enhance your server’s security, we strongly recommend setting up SSH keys instead of using password authentication.

If the Root Account Uses SSH Key Authentication

If you logged in to your root account using SSH keys, then password authentication is disabled for SSH. You will need to add a copy of your local public key to the new user’s [~/.ssh/authorized_keys] file to log in successfully.

Since your public key is already in the root account’s [~/.ssh/authorized_keys] file on the server, we can copy that file and directory structure to our new user account in our existing session.

The simplest way to copy the files with the correct ownership and permissions is with the [rsync] command. This will copy the root user’s [.ssh] directory, preserve the permissions, and modify the file owners, all in a single command. Make sure to change the example [sammy] portions of the command below to match your regular user’s name:

Note: The [rsync] command treats sources and destinations that end with a trailing slash differently than those without a trailing slash. When using [rsync] below, be sure that the source directory [~/.ssh] does not include a trailing slash (check to make sure you are not using [~/.ssh/]).
If you accidentally add a trailing slash to the command, [rsync] will copy the contents of the root account’s [~/.ssh] directory to the [sudo] user’s home directory instead of copying the entire [~/.ssh] directory structure. The files will be in the wrong location and SSH will not be able to find and use them.

rsync --archive --chown=sammy:sammy ~/.ssh /home/sammy

Now, open up a new terminal session and using SSH with your new username:

ssh sammy@your_server_ip

You should be logged in to the new user account without using a password. Remember, if you need to run a command with administrative privileges, type [sudo] before it like this:

sudo command_to_run

You will be prompted for your regular user password when using [sudo] for the first time each session (and periodically afterwards).

Completed initial server setup

Now that initial server setup has been finished, these articles might be useful:

• How To Install the Apache Web Server on Ubuntu 18.04 – In this guide, we’ll explain how to install an Apache web server on your Ubuntu 18.04 server.
• How To Secure Apache with Let’s Encrypt on Ubuntu 18.04 – In this tutorial, you will use the Let’s Encrypt client Certbot to obtain a free SSL certificate for Apache on Ubuntu 18.04 and set up your certificate to renew automatically.

break

Original Content by Justin Ellingwood and edited by the author of this post according to the Creative Commons Attribution-NonCommercial-ShareAlike 4.0 International License.