Book Image

Linux Shell Scripting Cookbook, Second Edition - Second Edition

Book Image

Linux Shell Scripting Cookbook, Second Edition - Second Edition

Overview of this book

The shell remains one of the most powerful tools on a computer system — yet a large number of users are unaware of how much one can accomplish with it. Using a combination of simple commands, we will see how to solve complex problems in day to day computer usage.Linux Shell Scripting Cookbook, Second Edition will take you through useful real-world recipes designed to make your daily life easy when working with the shell. The book shows the reader how to effectively use the shell to accomplish complex tasks with ease.The book discusses basics of using the shell, general commands and proceeds to show the reader how to use them to perform complex tasks with ease.Starting with the basics of the shell, we will learn simple commands with their usages allowing us to perform operations on files of different kind. The book then proceeds to explain text processing, web interaction and concludes with backups, monitoring and other sysadmin tasks.Linux Shell Scripting Cookbook, Second Edition serves as an excellent guide to solving day to day problems using the shell and few powerful commands together to create solutions.
Table of Contents (16 chapters)
Linux Shell Scripting Cookbook
Credits
About the Authors
About the Reviewers
www.PacktPub.com
Preface
Index

Making files immutable


Files on extended type filesystems, which are common in Linux (for example, ext2, ext3, ext4, and so on) can be made immutable using a certain type of file attributes. When a file is made immutable, any user or super user cannot remove the file until the immutable attribute is removed from the file. We can easily find out the filesystem type of any mounted partition 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 file system type (for example, ext3).

Making a file immutable is one of the methods for securing files from modification. An example would be to use it for the /etc/resolv.conf file which stores a list of DNS servers. A DNS server is used to convert domain names (such as packtpub.com) to IP addresses. Usually, the DNS server will be set to your ISP's DNS server. However, some people prefer to use a third-party server and they can modify /etc/resolv...