HOW TO VERIFY ISO IMAGE INTEGRITY

How to verify the integrity of a Linux distribution iso image

When we decide to install an operating system based on the Linux kernel, the first thing we do is to download its installation image, or ISO, from the official distribution website. Before proceeding with the actual installation, however, it is crucial to verify the integrity of the image, to be sure it is what it claims to be, and nobody has compromised it. In this tutorial we will see the basic steps we can follow to accomplish this task.

In this tutorial you will learn:

  • What is the basic difference between gpg encrypting and signing
  • How to download and import a gpg public key from a key server
  • How to verify a gpg signature
  • How to verify the checksum of an ISO

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How to trace system calls made by a process with strace on Linux

How to trace system calls made by a process with strace on Linux

There are times when it’s useful to inspect what a running application is doing under the hood, and what system calls it is performing during its execution. To accomplish such a task on Linux, we can use the strace utility. In this article we will see how to install it and we will learn its basic usage.

In this tutorial you will learn:

  • How to install strace
  • How to use strace to trace system calls made by a process
  • How to filter specifics system calls
  • How to attach to an already running process
  • How to generate a system call summary

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systemd-logo

Introduction to the Systemd journal

Systemd is nowadays the init system adopted by almost all Linux distributions, from Red Hat Enterprise Linux to Debian and Ubuntu. One of the things that made Systemd the target of a lot of critics is that it tries to be a lot more than a simple init system and tries to re-invent some Linux subsystems.

The traditional logging system used on Linux, for example was rsyslog, a modern version of the traditional syslog. Systemd introduced its own logging system: it is implemented by a daemon, journald, which stores logs in binary format into a “journal”, which can be queried by the journalctl utility.

In this tutorial we will learn some parameters we can use to modify the journald daemon behavior, and some examples of how to query the journal and format the output resulting from said queries.

In this tutorial you will learn:

  • How to change default journald settings
  • How journald can coexist with syslog
  • How to query the journal and some ways to format the queries output

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How to create incremental backups using rsync on Linux

How to create incremental backups using rsync on Linux

In previous articles, we already talked about how we can perform local and remote backups using rsync and how to setup the rsync daemon. In this tutorial we will learn a very useful technique we can use to perform incremental backups, and schedule them using the good old cron.

In this tutorial you will learn:

  • The difference between hard and symbolic links
  • What is an incremental backup
  • How the rsync –link-dest option works
  • How to create incremental backups using rsync
  • How to schedule backups using cron

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How to create compressed encrypted archives with tar and gpg

How to create compressed encrypted archives with tar and gpg

There are many reasons why you may want to create compressed encrypted file archives. You may want to create an encrypted backup of your personal files. Another possible scenario is that you may want to privately share content with a friend or colleague over the web or through cloud storage. Tar.gz files, or compressed tarballs, are created using the tar command. These tarballs are pretty much the standard go-to format for archives on GNU/Linux, however they are not encrypted. In the above scenarios that we mentioned it is often desirable to have encryption in order to secure your data. This is where gpg comes in.

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How to install, configure, and use mutt with a gmail account on Linux

How to install, configure, and use mutt with a gmail account on Linux

Email reader programs such as Thunderbird or Evolution are great, but sometimes they can feel bloated. If you found yourself working mainly from CLI, you may find useful to learn how to install and configure Mutt, a command line email client: that’s what we will do in this tutorial.

In this tutorial you will learn:

  • How to install Mutt
  • How to configure Mutt to be used with a gmail account
  • How to store sensitive information in an encrypted file and source it from the main Mutt configuration
  • How to setup some macros to easily switch between mailbox directories

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Using GNU screen with examples

Using GNU screen with examples

Have you even been in the situation where you were running a 3 hour copy or script on a remote machine, only to find that it broke at 2h 45min because your network connection or SSH connection dropped momentarily? If so, you know how painful that feels 🙂 Welcome to GNU screen, the utility which allows you to start a separate shell which will not be interrupted if your network connection breaks. Read on to discover how to use it and more!

In this tutorial you will learn:

  • How to install and use the GNU screen utility
  • How to configure the GNU screen utility to function better
  • Basic usage examples on how to use the GNU screen utility from the Bash command line

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List of users on a Linux system

How to list users on Linux

User management is an important part of Linux administration, so it’s essential to know about all the user accounts on a Linux system and how to disable user accounts, etc. In this guide, we’ll show you how to list the current users via command line and GUI. This will include a GNOME desktop environment as well as KDE.

In this tutorial you will learn:

  • How to list users via command line
  • How to list users on GNOME GUI
  • How to list users on KDE GUI

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Tips & Tricks with Netcat command on Linux

Tips & Tricks with Netcat command on Linux

Netcat is a versatile networking utility which can be used for reading from and writing to TCP and UDP connections on arbitrary ports (as with other utilities used on Linux, ports below 1024 require root/sudo privileges). By default netcat uses TCP connections, but UDP can be specified with the -u flag. Netcat can be used as both a server and a client. When used as a server the -l flag is used to listen for a connection. Similar to the cat command, netcat can receive information from stdin and write to stdout making it great for workflows involving pipes and redirects. The nc command is typically used to evoke netcat for ease of use.

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How to use zip on Linux

How to use zip on Linux

Compressed files with the .zip extension are commonplace throughout Windows systems, as it’s been the native file compression method for the operating system since many years ago. On a Linux system, the nearest equivalent would have to be tar files and various methods of compression like gzip.

There are a few reasons why you may need to create or open .zip files on Linux. When sharing files with a Windows user, it’d definitely be better to send them a .zip file than a file with Linux based compression, and you may come across an occasional zip archive online or from a friend that you need to open.

In this guide, we’ll show you how to use zip on Linux to open or create compressed .zip archives on both the command line and GUI.

In this tutorial you will learn:

  • How to use zip and unzip via command line
  • How to use zip and unzip via GUI

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