Prerequisites

To complete this tutorial, you will require root access on at least three Ubuntu 14.04 servers. Instructions to set up root access can be found here (steps 3 and 4): Initial Server Setup with Ubuntu 14.04.

If you are planning on using this in your own environment, you will have to plan out how your servers need to access each other, and adapt the examples presented in this tutorial to your own needs. If you are adapting this to your own setup, be sure to substitute the highlighted values in the examples with your own values.

If you would like to follow this tutorial exactly, create two VPSs in the same datacenter, with private networking, and create another VPS in a separate datacenter. We will create two VPSs in the NYC2 datacenter and one in AMS2 datacenter with the following names:

• externalnyc: All of the VPN nodes will connect to this server, and the connection must be maintained for proper VPN functionality. Additional servers can be configured in a similarly to this one to provide redundancy, if desired.
• internalnyc: Connects to externalnyc VPN node using its private network interface
• ams1: Connects to externalnyc VPN node over the public Internet

Tinc Configuration

Tinc uses a “netname” to distinguish one Tinc VPN from another (in case of multiple VPNs), and it is recommended to use a netname even if you are only planning on configuring one VPN. We will call our VPN “netname” for simplicity.

The ping should work fine, and you should see some debug output in the other windows about the connection on the VPN. This indicates that ams1 is able to communicate over the VPN through externalnyc to internalnyc. This indicates that ams1 is able to communicate over the VPN through externalnyc to internalnyc.

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When you first create a new Debian 8 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 One: Root Login

To log into your server initially, you will need to know your server’s public IP address and the password for the “root” user’s account. For servers on DigitalOcean, you will receive an email with your server credentials and the server’s IP address.

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 actually 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.

In this guide, we’ll help you 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. The first step is to log into your server, and the only account we start out with is the root account. We can connect to the server by using the ssh command in the terminal. The command will look like this:

ssh root@server_ip_address

You will most likely see a warning in your terminal window that looks like this:

The authenticity of host '123.123.123.123 (123.123.123.123)' can't be established.
ECDSA key fingerpring is
79:95:46:1a:ab:37:11:8e:86:54:36:38:bb:3c:fa:c0.
Are you sure you want to continue connecting (yes/no)?

Here, your computer is basically telling you that it doesn’t recognize your remote server. Since this is your first time connecting, this is completely expected. Go ahead and type “yes” to accept the connection. Afterwards, you’ll need to enter the password for the root account.

Step Two: Change Your Password

You are not likely to remember the password that is currently set for your root account. You can change the password to something you will remember more easily by typing:

passwd

It will ask you to enter and confirm your new password. During this process, you will not see anything show up on your screen as you type. This is intentional and is there so that people looking over your shoulder cannot guess your password by the number of characters.

Step Three: Create a New User

At this point, we’re prepared to add the new user account that we will use to log in from now on. I’m going to name my user “demo”, but you can select whatever name you’d like:

adduser demo

You will be asked a few questions, starting with the account password. Fill out the 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 Four: Root Privileges

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 “sudo” 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 account, we need to use a command called visudo. This will open a configuration file:

visudo

Scroll down until you find a section that deals with user privileges. It will look similar to this:

# User privilege specification
root    ALL=(ALL:ALL) ALL

While this might look complicated, we don’t need to worry about that. All we need to do is add another line below it that follows the format, replacing “demo” with the user you created:

# User privilege specification
root    ALL=(ALL:ALL) ALL
demo    ALL=(ALL:ALL) ALL

After this is done, press CTRL-X to exit. You will have to type “Y” to save the file and then press “ENTER” to confirm the file location.

Step Five: Configure SSH (Optional)

Now that we have our new account, we can secure our server a little bit by modifying the configuration of SSH (the program that allows us to log in remotely). Begin by opening the configuration file with your text editor as root:

nano /etc/ssh/sshd_config

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Step One: Install Nginx

We can install Nginx easily because the Ubuntu team provides an Nginx package in its default repositories. Since this is our first interaction with the apt packaging system in this session, we should update our local package index before we begin so that we are using the most up-to-date information. Afterwards, we will install nginx:

sudo apt-get update
sudo apt-get install nginx

You will probably be prompted for your user’s password. Enter it to confirm that you wish to complete the installation. The appropriate software will be downloaded to your server and then automatically installed.

Step Two: Check your Web Server

You can access the default Nginx landing page to confirm that the software is running properly by visiting your server’s domain name or public IP address in your web browser.

If you do not have a spare domain name, or have no need for one, you can use your server’s public IP address. If you do not know your server’s IP address, you can get it a few different ways from the command line.

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In computing, a firewall is a network security system that monitors and controls the incoming and outgoing network traffic based on predetermined security rules. A firewall typically establishes a barrier between a trusted, secure internal network and another outside network, such as the Internet, that is assumed to not be secure or trusted.

Getting Started

• If you are just getting started with configuring your firewall.
• Most of the rules that are described here assume that your iptables is set to DROP incoming traffic, through the default input policy, and you want to selectively allow traffic in.
• Use whichever subsequent sections are applicable to what you are trying to achieve. Most sections are not predicated on any other, so you can use the examples below independently.
• Use the Contents menu on the right side of this page (at wide page widths) or your browser’s find function to locate the sections you need.
• Copy and paste the command-line examples given, substituting the values in red with your own values.

Keep in mind that the order of your rules matter. All of these iptables commands use the -A option to append the new rule to the end of a chain. If you want to put it somewhere else in the chain, you can use the -I option which allows you to specify the position of the new rule (or simply place it at the beginning of the chain by not specifying a rule number).

Allow Loopback Connections

The loopback interface, also referred to as lo, is what a computer uses to for network connections to itself. For example, if you run ping localhost or ping 127.0.0.1, your server will ping itself using the loopback. The loopback interface is also used if you configure your application server to connect to a database server with a “localhost” address. As such, you will want to be sure that your firewall is allowing these connections.

Conclusion

That should cover many of the commands that are commonly used when configuring an iptables firewall. Of course, iptables is a very flexible tool so feel free to mix and match the commands with different options to match your specific needs if they aren’t covered here. Continue reading this guide at Digital Ocean. This article has been used as an example of an Ecko WordPress theme. This work is licensed under a Creative Commons Attribution-NonCommercial-ShareAlike 4.0 International License.

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