Book Image

Essential Linux Commands

By : Paul Olushile
Book Image

Essential Linux Commands

By: Paul Olushile

Overview of this book

The role of a system administrator is ever-evolving, with the Linux command line at its core. This makes Linux command-line mastery an essential skill to demonstrate your ability to efficiently manage and maintain systems efficiently. Essential Linux Commands addresses a diverse range of topics, including package management, file manipulation, networking strategies, system monitoring, and diagnostic tools. Each command is intricately explained to eliminate any ambiguity, ensuring ease of implementation in real-world scenarios. This book explains how to use SELinux to maintain security, run Linux machines on AWS Cloud, and transfer and download files to remote systems. With the help of practical examples and use cases, you’ll not only gain a thorough understanding of a command’s syntax but also grasp its functional breadth and limitations. The book also explores commands frequently used by system administrators to check network card statistics and firewall rules. Whether you’re a beginner or an experienced administrator, this book is an invaluable resource, filling in the gaps in your skill set and helping you improve your skills and expertise in Linux administration.
Table of Contents (20 chapters)
1
Part 1:Server Installations and Management Commands
5
Part 2:Frequently Used Commands – Part 1
9
Part 3:Frequently Used Commands – Part 2
15
Part 4:Linux Security and the Cloud

pwck, chage, and passwd commands

The pwck command is a Linux system administration tool that is used to verify the consistency of the passwd, shadow, and group files. The purpose of the command is to ensure that the user accounts and groups listed in these files are valid and to detect any inconsistencies between them. It is useful in maintaining the integrity and security of a Linux system, as it can help to identify and correct errors that may arise due to manual edits of these files. For example, if a user account exists in the passwd file but not in the shadow file, pwck will detect this and prompt the user to fix the inconsistency. Let’s take a look at some examples using this tool:

  • Verify the consistency of the passwd file with sudo pwck /etc/passwd.

    The following output from the pwck command checks the consistency of the /etc/passwd file on our Linux system:

Figure 2.22 – Checking the consistency of the /etc/passwd file

Figure 2.22 – Checking the consistency of the /etc/passwd file

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