Category Archives: Linux

Linux

How To Protect WordPress with Fail2Ban on Ubuntu 14.04

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Introduction

WordPress is a very robust content-management system (CMS) that is free and open source. Because anyone can comment, create an account, and post on WordPress, many malicious actors have created networks of bots and servers that compromise and spam WordPress sites through brute-force attacks. The tool Fail2ban is useful in preventing unauthorized access to both your Droplet and your WordPress site. It notes suspicious or repeated login failures and proactively bans those IPs by modifying firewall rules for your Droplet.

In this guide, we will be using version 0.9.3 of Fail2ban on an Ubuntu 14.04 LAMP server, and integrating it with WordPress by using a spam log plugin.

Prerequisites

To complete this guide, you need

Continue reading How To Protect WordPress with Fail2Ban on Ubuntu 14.04 →

Linux

How to Set Up Apache Traffic Server as a Reverse-Proxy on Ubuntu 14.04

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Introduction

Apache Traffic Server is a highly scalable caching proxy server capable of handling large volumes of concurrent requests while maintaining a very low latency. Compared to other popular proxy servers, such as Varnish or Squid, it usually consumes less memory and responds faster. It is also designed to make the most of modern multi-core processors. Depending on your requirements, you can use it as a reverse proxy or as a forward proxy.

This tutorial will cover how to install Apache Traffic Server on Ubuntu 14.04 and configure it to behave as a caching reverse proxy.

Prerequisites

To follow this tutorial, you will need:

Continue reading How to Set Up Apache Traffic Server as a Reverse-Proxy on Ubuntu 14.04 →

Linux

Understanding Nginx HTTP Proxying, Load Balancing, Buffering, and Caching

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Understanding Nginx HTTP Proxying, Load Balancing, Buffering, and Caching

Introduction

In this guide, we will discuss Nginx’s http proxying capabilities, which allow Nginx to pass requests off to backend http servers for further processing. Nginx is often set up as a reverse proxy solution to help scale out infrastructure or to pass requests to other servers that are not designed to handle large client loads.

Along the way, we will discuss how to scale out using Nginx’s built-in load balancing capabilities. We will also explore buffering and caching to improve the performance of proxying operations for clients.

General Proxying Information

If you have only used web servers in the past for simple, single server configurations, you may be wondering why you would need to proxy requests.

One reason to proxy to other servers from Nginx is the ability to scale out your infrastructure. Nginx is built to handle many concurrent connections at the same time. This makes it ideal for being the point-of-contact for clients. The server can pass requests to any number of backend servers to handle the bulk of the work, which spreads the load across your infrastructure. This design also provides you with flexibility in easily adding backend servers or taking them down as needed for maintenance.

Another instance where an http proxy might be useful is when using an application servers that might not be built to handle requests directly from clients in production environments. Many frameworks include web servers, but most of them are not as robust as servers designed for high performance like Nginx. Putting Nginx in front of these servers can lead to a better experience for users and increased security.

Proxying in Nginx is accomplished by manipulating a request aimed at the Nginx server and passing it to other servers for the actual processing. The result of the request is passed back to Nginx, which then relays the information to the client. The other servers in this instance can be remote machines, local servers, or even other virtual servers defined within Nginx. The servers that Nginx proxies requests to are known as upstream servers.

Nginx can proxy requests to servers that communicate using the http(s), FastCGI, SCGI, and uwsgi, or memcached protocols through separate sets of directives for each type of proxy. In this guide, we will be focusing on the http protocol. The Nginx instance is responsible for passing on the request and massaging any message components into a format that the upstream server can understand. Continue reading Understanding Nginx HTTP Proxying, Load Balancing, Buffering, and Caching →

Linux

How To Set Up an OpenVPN Server on Ubuntu 14.04

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How To Set Up an OpenVPN Server on Ubuntu 14.04

Introduction

Want to access the Internet safely and securely from your smartphone or laptop when connected to an untrusted network such as the WiFi of a hotel or coffee shop? A Virtual Private Network (VPN) allows you to traverse untrusted networks privately and securely to your DigitalOcean Droplet as if you were on a secure and private network. The traffic emerges from the Droplet and continues its journey to the destination.

When combined with HTTPS connections, this setup allows you to secure your wireless logins and transactions. You can circumvent geographical restrictions and censorship, and shield your location and unencrypted HTTP traffic from the untrusted network.

OpenVPN is a full-featured open source Secure Socket Layer (SSL) VPN solution that accommodates a wide range of configurations. In this tutorial, we’ll set up an OpenVPN server on a Droplet and then configure access to it from Windows, OS X, iOS and Android. This tutorial will keep the installation and configuration steps as simple as possible for these setups.

Note: OpenVPN can be installed automatically on your Droplet by adding this script to its User Data when launching it. Check out this tutorial to learn more about Droplet User Data.

Continue reading How To Set Up an OpenVPN Server on Ubuntu 14.04 →

Linux

How To Set Up Apache Virtual Hosts on Ubuntu 14.04 LTS

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How To Set Up Apache Virtual Hosts on Ubuntu 14.04 LTS

Introduction

The Apache web server is the most popular way of serving web content on the internet. It accounts for more than half of all active websites on the internet and is extremely powerful and flexible.

Apache breaks its functionality and components into individual units that can be customized and configured independently. The basic unit that describes an individual site or domain is called a virtual host.

These designations allow the administrator to use one server to host multiple domains or sites off of a single interface or IP by using a matching mechanism. This is relevant to anyone looking to host more than one site off of a single VPS.

Each domain that is configured will direct the visitor to a specific directory holding that site’s information, never indicating that the same server is also responsible for other sites. This scheme is expandable without any software limit as long as your server can handle the load.

In this guide, we will walk you through how to set up Apache virtual hosts on an Ubuntu 14.04 VPS. During this process, you’ll learn how to serve different content to different visitors depending on which domains they are requesting. Continue reading How To Set Up Apache Virtual Hosts on Ubuntu 14.04 LTS →

Linux

How To Set Up SSH Keys

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How To Set Up SSH Keys

About SSH Keys

SSH keys provide a more secure way of logging into a virtual private server with SSH than using a password alone. While a password can eventually be cracked with a brute force attack, SSH keys are nearly impossible to decipher by brute force alone. Generating a key pair provides you with two long string of characters: a public and a private key. You can place the public key on any server, and then unlock it by connecting to it with a client that already has the private key. When the two match up, the system unlocks without the need for a password. You can increase security even more by protecting the private key with a passphrase.

Step One—Create the RSA Key Pair

The first step is to create the key pair on the client machine (there is a good chance that this will just be your computer): Continue reading How To Set Up SSH Keys →

Linux

Add Swap on Ubuntu 14.04

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How To Add Swap on Ubuntu 14.04

Introduction

One of the easiest way of increasing the responsiveness of your server and guarding against out of memory errors in your applications is to add some swap space. Swap is an area on a hard drive that has been designated as a place where the operating system can temporarily store data that it can no longer hold in RAM.

Basically, this gives you the ability to increase the amount of information that your server can keep in its working “memory”, with some caveats. The space on the hard drive will be used mainly when space in RAM is no longer sufficient for data.

The information written to disk will be slower than information kept in RAM, but the operating system will prefer to keep running application data in memory and use swap for the older data. Overall, having swap space as a fall back for when your system’s RAM is depleted is a good safety net.

In this guide, we’ll cover how to create and enable a swap file on an Ubuntu 14.04 server.

Check the System for Swap Information

Before we begin, we will take a look at our operating system to see if we already have some swap space available. We can have multiple swap files or swap partitions, but generally one should be enough.

We can see if the system has any configured swap by typing: Continue reading Add Swap on Ubuntu 14.04 →

Linux

Understanding the Nginx Configuration File Structure and Configuration Contexts

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Understanding the Nginx Configuration File Structure and Configuration Contexts

Introduction

Nginx is a high performance web server that is responsible for handling the load of some of the largest sites on the internet. It is especially good at handling many concurrent connections and excels at serving static content.

While many users are aware of Nginx’s capabilities, new users are often confused by some of the conventions they find in Nginx configuration files. In this guide, we will focus on discussing the basic structure of an Nginx configuration file along with some guidelines on how to design your files.

Understanding Nginx Configuration Contexts

This guide will cover the basic structure found in the main Nginx configuration file. The location of this file will vary depending on how you installed the software on your machine. For many distributions, the file will be located at /etc/nginx/nginx.conf. If it does not exist there, it may also be at /usr/local/nginx/conf/nginx.conf or /usr/local/etc/nginx/nginx.conf.

One of the first things that you should notice when looking at the main configuration file is that it appears to be organized in a tree-like structure, defined by sets of brackets (that look like { and }). In Nginx parlance, the areas that these brackets define are called “contexts” because they contain configuration details that are separated according to their area of concern. Basically, these divisions provide an organizational structure along with some conditional logic to decide whether to apply the configurations within.

Because contexts can be layered within one another, Nginx provides a level of directive inheritance. As a general rule, if a directive is valid in multiple nested scopes, a declaration in a broader context will be passed on to any child contexts as default values. The children contexts can override these values at will. It is worth noting that an override to any array-type directives will replace the previous value, not append to it.

Directives can only be used in the contexts that they were designed for. Nginx will error out on reading a configuration file with directives that are declared in the wrong context. The Nginx documentation contains information about which contexts each directive is valid in, so it is a great reference if you are unsure.

Below, we’ll discuss the most common contexts that you’re likely to come across when working with Nginx. Continue reading Understanding the Nginx Configuration File Structure and Configuration Contexts →

Linux

Set Up Nginx Server Blocks (Virtual Hosts) on Ubuntu 14.04 LTS

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Introduction

When using the Nginx web server, server blocks (similar to the virtual hosts in Apache) can be used to encapsulate configuration details and host more than one domain off of a single server.

In this guide, we’ll discuss how to configure server blocks in Nginx on an Ubuntu 14.04 server.

Prerequisites

We’re going to be using a non-root user with sudo privileges throughout this tutorial. If you do not have a user like this configured, you can make one by following steps 1-4 in our Ubuntu 14.04 initial server setup guide.

You will also need to have Nginx installed on your server. If you want an entire LEMP (Linux, Nginx, MySQL, and PHP) stack on your server, you can follow our guide on setting up a LEMP stack in Ubuntu 14.04. If you only need Nginx, you can install it by typing:

sudo apt-get update
sudo apt-get install nginx

When you have fulfilled these requirements, you can continue on with this guide.

For demonstration purposes, we’re going to set up two domains with our Nginx server. The domain names we’ll use in this guide are example.com and test.com.

You can find a guide on how to set up domain names with DigitalOcean here. If you do not have two spare domain names to play with, use dummy names for now and we’ll show you later how to configure your local computer to test your configuration.

Step One — Set Up New Document Root Directories

By default, Nginx on Ubuntu 14.04 has one server block enabled by default. It is configured to serve documents out of a directory at:

/usr/share/nginx/html

We won’t use the default since it is easier to work with things in the /var/www directory. Ubuntu’s Nginx package does not use /var/www as its document root by default due to a Debian policy about packages utilizing /var/www. Continue reading Set Up Nginx Server Blocks (Virtual Hosts) on Ubuntu 14.04 LTS →

Linux

Install Linux, nginx, MySQL, PHP (LEMP) stack on Ubuntu 14.04

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Introduction

The LEMP software stack is a group of software that can be used to serve dynamic web pages and web applications. This is an acronym that describes a Linux operating system, with an Nginx web server. The backend data is stored in MySQL and the dynamic processing is handled by PHP.

In this guide, we will demonstrate how to install a LEMP stack on an Ubuntu 14.04 server. The Ubuntu operating system takes care of the first requirement. We will describe how to get the rest of the components up and running.

Note: The LEMP Stack can be installed automatically on your Droplet by adding this script to its User Data when launching it. Check out this tutorial to learn more about Droplet User Data.

Prerequisites

Before you complete this tutorial, you should have a regular, non-root user account on your server with sudo privileges. You can learn how to set up this type of account by completing steps 1-4 in our Ubuntu 14.04 initial server setup.

Once you have your account available, sign into your server with that username. You are now ready to begin the steps outlined in this guide. Continue reading Install Linux, nginx, MySQL, PHP (LEMP) stack on Ubuntu 14.04 →