Book Image

Mastering Linux Administration

By : Alexandru Calcatinge, Julian Balog
Book Image

Mastering Linux Administration

By: Alexandru Calcatinge, Julian Balog

Overview of this book

Linux plays a significant role in modern data center management and provides great versatility in deploying and managing your workloads on-premises and in the cloud. This book covers the important topics you need to know about for your everyday Linux administration tasks. The book starts by helping you understand the Linux command line and how to work with files, packages, and filesystems. You'll then begin administering network services and hardening security, and learn about cloud computing, containers, and orchestration. Once you've learned how to work with the command line, you'll explore the essential Linux commands for managing users, processes, and daemons and discover how to secure your Linux environment using application security frameworks and firewall managers. As you advance through the chapters, you'll work with containers, hypervisors, virtual machines, Ansible, and Kubernetes. You'll also learn how to deploy Linux to the cloud using AWS and Azure. By the end of this Linux book, you'll be well-versed with Linux and have mastered everyday administrative tasks using workflows spanning from on-premises to the cloud. If you also find yourself adopting DevOps practices in the process, we'll consider our mission accomplished.
Table of Contents (20 chapters)
Section 1: Linux Basic Administration
Section 2: Advanced Linux Server Administration
Section 3: Cloud Administration

Working with firewalls

Traditionally, a firewall is a network security device that's placed between two networks. It monitors the network traffic and controls access to these networks. Generally speaking, a firewall protects a local network from unwanted intrusion or attacks from the outside. But a firewall can also block unsolicited locally originated traffic targeting the public internet. Technically, a firewall allows or blocks incoming and outgoing network traffic based on specific security rules.

For example, a firewall can block all but a select set of inbound networking protocols (such as SSH and HTTP/HTTPS). It may also block all but approved hosts within the local network from establishing specific outbound connections, such as allowing outbound SMTP connections that originated exclusively from the local email servers.

The following diagram shows a simple firewall deployment regulating traffic between a local network and the internet:

Figure 9.44 – A simple firewall diagram