Book Image

Linux Shell Scripting Cookbook - Third Edition

By : Clif Flynt, Sarath Lakshman, Shantanu Tushar
Book Image

Linux Shell Scripting Cookbook - Third Edition

By: Clif Flynt, Sarath Lakshman, Shantanu Tushar

Overview of this book

The shell is the most powerful tool your computer provides. Despite having it at their fingertips, many users are unaware of how much the shell can accomplish. Using the shell, you can generate databases and web pages from sets of files, automate monotonous admin tasks such as system backups, monitor your system's health and activity, identify network bottlenecks and system resource hogs, and more. This book will show you how to do all this and much more. This book, now in its third edition, describes the exciting new features in the newest Linux distributions to help you accomplish more than you imagine. It shows how to use simple commands to automate complex tasks, automate web interactions, download videos, set up containers and cloud servers, and even get free SSL certificates. Starting with the basics of the shell, you will learn simple commands and how to apply them to real-world issues. From there, you'll learn text processing, web interactions, network and system monitoring, and system tuning. Software engineers will learn how to examine system applications, how to use modern software management tools such as git and fossil for their own work, and how to submit patches to open-source projects. Finally, you'll learn how to set up Linux Containers and Virtual machines and even run your own Cloud server with a free SSL Certificate from letsencrypt.org.
Table of Contents (14 chapters)

Making files immutable

The Read, Write, Execute, and Setuid fields are common to all Linux file systems. The Extended File Systems (ext2, ext3, and ext4) support more attributes.

One of the extended attributes makes files immutable. When a file is made immutable, any user or super user cannot remove the file until the immutable attribute is removed from the file. You can determine the type of filesystem with the df -T command, or by looking at the /etc/mtab file. The first column of the file specifies the partition device path (for example, /dev/sda5) and the third column specifies the filesystem type (for example, ext3).

Making a file immutable is one method for securing files from modification. One example is to make the /etc/resolv.conf file immutable. The resolv.conf file stores a list of DNS servers, which convert domain names (such as packtpub.com) to IP addresses. The DNS server is usually your ISP's...