Book Image

Learn Linux Quickly

By : Ahmed AlKabary
Book Image

Learn Linux Quickly

By: Ahmed AlKabary

Overview of this book

Linux is one of the most sought-after skills in the IT industry, with jobs involving Linux being increasingly in demand. Linux is by far the most popular operating system deployed in both public and private clouds; it is the processing power behind the majority of IoT and embedded devices. Do you use a mobile device that runs on Android? Even Android is a Linux distribution. This Linux book is a practical guide that lets you explore the power of the Linux command-line interface. Starting with the history of Linux, you'll quickly progress to the Linux filesystem hierarchy and learn a variety of basic Linux commands. You'll then understand how to make use of the extensive Linux documentation and help tools. The book shows you how to manage users and groups and takes you through the process of installing and managing software on Linux systems. As you advance, you'll discover how you can interact with Linux processes and troubleshoot network problems before learning the art of writing bash scripts and automating administrative tasks with Cron jobs. In addition to this, you'll get to create your own Linux commands and analyze various disk management techniques. By the end of this book, you'll have gained the Linux skills required to become an efficient Linux system administrator and be able to manage and work productively on Linux systems.
Table of Contents (24 chapters)

Our first cron job

The following diagram shows you the typical format for a cron job:

Figure 1: A cron job format

Cron jobs are user-specific, and so each user has their own list of cron jobs. For example, the user elliot can run the command crontab -l to display his their of cron jobs:

elliot@ubuntu-linux:~$ crontab -l 
no crontab for elliot

Currently, the user elliot doesn't have any cron jobs.

Let's go ahead and create Elliot's first cron job. We will create a cron job that will run every minute, and it will simply append the line "A minute has passed." to the file /home/elliot/minutes.txt.

You can run the command crontab -e to edit or create cron jobs:

elliot@ubuntu-linux:~$ crontab -e

Now add the following line and then save and exit:

* * * * * echo "A minute has passed." >> /home/elliot/minutes.txt

After you exit, you will see the message: "crontab: installing new crontab":

elliot@ubuntu-linux:~$ crontab -e 
crontab: installing...