Getting Started with Ubuntu 16.04 LTS

A few configuration changes are needed as part of the basic setup with a new Ubuntu 16.04 LTS server. This article will provide a comprehensive list of those basic configurations and help to improve the security and usability of your server while creating a solid foundation to build on.

Root Login

First, we need to get logged into the server. To log in, you will need the Ubuntu server’s public IP address and the password for the “root” user account. If you are new to server administration, you may want to check out our SSH tutorial.
Start by logging in as the root user with the command below (be sure to enter your server’s public IP address):
ssh root@server_ipEnter the root password mentioned earlier and hit “Enter.” You may be prompted to change the root password upon first logging in.


Root User

The root user is the default administrative user within a Linux(Ubuntu) environment that has extensive privileges. Regular use of the root user account is discouraged as part of the power inherent within the root account is its ability to make very adverse changes. The control of this user can lead to many different issues, even if those changes made are by accident.
The solution is to set up an alternative user account with reduced privileges and make it a “superuser.”


Create a New User

Once you are logged in as root, we need to add a new user account to the server. Use the below example to create a new user on the server. Replace “test1” with a username that you like:

adduser test1

You will be asked a few questions, starting with the account password.
Be sure to enter a strong password and fill in any of the additional information. This information is optional, and you can just hit ENTER in any field you wish to skip.


Root Privileges

We should now have a new user account with regular account privileges. That said, there may be a time when we need to perform administrative level tasks.
Rather than continuously switching back and forth with the root account, we can set up what is called a “superuser” or root privileges for a regular account. Granting a regular user administrative rights will allow this user to run commands with administrative(root) privileges by putting the word “sudo” before each command.
To give these privileges to the new user, we need to add the new user to the sudo group. On Ubuntu 16.04, users that belong to the sudo group are allowed to use the sudo command by default.
While logged in as root, run the below command to add the newly created user to the sudo group:

usermod -aG sudo test1

That user can now run commands with superuser privileges using the sudo command!


Public Key Authentication

Next, we recommend that you set up public key authentication for the new user. Setting up a public key will configure the server to require a private SSH key when you try to log in, adding another layer of security to the server. To setup Public Key Authentication, please follow the steps outlined in our “Using-SSH-Keys” article.


Disable Password Authentication

Following the steps outlined in the previously mentioned “Using-SSH-Keys” article, results in the new user ability to use the SSH key to log in. Once you have confirmed the SSH Key is working, we can proceed with disabling password-only authentication to increase the server’s security even further. Doing so will restrict SSH access to your server to public key authentication only, reducing entry to your Ubuntu server via the keys installed on your computer.

You should only disable password authentication if you successfully installed and tested the public key as recommended. Otherwise, you have the potential of being locked out of your server.

To disable password authentication on the server, start with the sshd configuration file. Log into the server as root and make a backup of the sshd_config file:

cp /etc/ssh/sshd_config /etc/ssh/sshd_config.backup

Now open the SSH daemon configuration using nano:

nano /etc/ssh/sshd_config

Find the line for “PasswordAuthentication” and delete the preceding “#” to uncomment the line. Change its value from “yes” to “no” so that it looks like this:

PasswordAuthentication no

The below settings are important for key-only authentication and set by default. Be sure to double check to configure as shown:

PubkeyAuthentication yes
ChallengeResponseAuthentication no

Once done, save and close the file with CTRL-X, then Y, then ENTER.

We need to reload/restart the SSH daemon to recognize the changes with the below command:

systemctl reload sshd

Password authentication is now disabled, and access restricted to SSH key authentication.

Set Up a Basic Firewall

The default firewall management on Ubuntu is iptables. Iptables offers powerful functionality. However, it has a complex syntax that can be confusing for a lot of users. A more user-friendly language can make managing your firewall much easier.
Enter Uncomplicated Firewall (UFW); the recommended alternative to iptables for managing firewall rules on Ubuntu 16.04. Most standard Ubuntu installations are built with UFW by default. A few simple commands can install where UFW is not present.


Install UFW

Before performing any new install, it is always best practice to run a package update; you’ll need root SSH access to the server. Updating helps to ensure that the latest version of the software package. Use the below commands to update the server packages and then we can proceed with the UFW install:

apt update

apt upgrade

With the packages updates, it’s time for us to install UFW:
apt install ufwOnce the above command completes, you can confirm the UFW install with a simple version command:
ufw --version

UFW is essentially a wrapper for iptables and netfilters, so there is no need to enable or restart the service with systemd. Though UFW is installed, it is not “ON” by default. The firewall still needs to be enabled with the below command:

ufw enable

Recreating any pre-existing iptables rules is necessary for UFW. It is best to set up the basic firewall rules then enable UFW to ensure you are not accidentally locked out while working via SSH.


Using UFW

UFW is easy to learn! Various programs can provide support for UFW in the form of app profiles which are pretty straightforward. Using the app profiles, you can allow or deny access for specific applications. Below are a few examples of how to view and manage these profiles:

  • List all the profiles provided by currently installed packages:

ufw app list

Available applications:
Apache Full
Apache Secure

  • Allow “full” access to Apache on port 80 and 443:

ufw allow "Apache Full"

Rule added
Rule added (v6)

  • Allow SSH access:

ufw allow "OpenSSH"

Rule added
Rule added (v6)

  • View the detailed status of UFW:

ufw status verbose

Status: active
Logging: on (low)
Default: deny (incoming), allow (outgoing), disabled (routed)
New profiles: skip

To                         Action From
--                         ------ ----
22/tcp (OpenSSH)           ALLOW IN Anywhere           
22/tcp (OpenSSH (v6))      ALLOW IN Anywhere (v6)

As you can see, the App profiles feature in UFW makes it easy to manage services in your firewall. Newer servers will not have many profiles to start with. As you continue to install more applications, any that support UFW are included in the list of profiles shown when you run the ufw app list command.

If you have completed all of the configurations outlined above, you now have a solid foundation to start installing any other software you need on your new Ubuntu 16.04 server.


Enable Root Login via SSH

By default SSH comes configured in a way that disables root user logins. This is done as a security precaution and means that you cannot directly login as the root user over SSH. However you can usually get around the need for root ssh login by using the sudo command. In some cases though it’s just more convenient to get directly logged in as root.

Continue reading “Enable Root Login via SSH”