Book Image

Mastering CentOS 7 Linux Server

By : Mohamed Alibi, BHASKARJYOTI ROY
Book Image

Mastering CentOS 7 Linux Server

By: Mohamed Alibi, BHASKARJYOTI ROY

Overview of this book

Most server infrastructures are equipped with at least one Linux server that provides many essential services, both for a user's demands and for the infrastructure itself. Setting up a sustainable Linux server is one of the most demanding tasks for a system administrator to perform. However, learning multiple, new technologies to meet all of their needs is time-consuming. CentOS 7 is the brand new version of the CentOS Linux system under the RPM (Red Hat) family. It is one of the most widely-used operating systems, being the choice of many organizations across the world. With the help of this book, you will explore the best practices and administration tools of CentOS 7 Linux server along with implementing some of the most common Linux services. We start by explaining the initial steps you need to carry out after installing CentOS 7 by briefly explaining the concepts related to users, groups, and right management, along with some basic system security measures. Next, you will be introduced to the most commonly used services and shown in detail how to implement and deploy them so they can be used by internal or external users. Soon enough, you will be shown how to monitor the server. We will then move on to master the virtualization and cloud computing techniques. Finally, the book wraps up by explaining configuration management and some security tweaks. All these topics and more are covered in this comprehensive guide, which briefly demonstrates the latest changes to all of the services and tools with the recent shift from CentOS 6 to CentOS 7.
Table of Contents (16 chapters)
Mastering CentOS 7 Linux Server
Credits
About the Authors
About the Reviewers
www.PacktPub.com
Preface
Index

Securing SSH and the root login configuration


For this section, we are going to show some basic and advanced ways to secure the SSH service to mitigate more threats. We will need to make some minor changes to the /etc/ssh/sshd_config file. We will explain every line as we change it gradually:

$ sudo nano /etc/ssh/sshd_config

Uncomment the SSH version 2 line to use only the newer version of SSH, which is more secure and reliable. The line should look like the following:

Protocol 2

We can limit users' access to restrict some users from accessing the server. We do this using SSH:

DenyUsers Baduser1 baduser2

Then we can set up the time out for the SSH connection to always close the sessions that are not active for a defined period of time. We need to set the countdown to start from the moment the session became idle:

ClientAliveInterval 360
ClientAliveCountMax 0

Then we can disable the root login using SSH:

PermitRootLogin no

In addition, we can disable empty password usage, whereby users do...