HOW TO VERIFY CHECKSUM IN LINUX

WHAT IS CHECKSUM IN LINUX?

Checksum is like a digital fingerprint of a file. In technical terms,
A checksum is a small-sized datum from a block of digital data for the purpose of detecting errors which may have been introduced during its transmission or storage.
Well, checksum is a long string of data containing various letters and numbers. You’ll generally find them while downloading files from the web, e.g. Linux distribution image, software packages etc.
Most common use of checksum is in checking if the downloaded file is corrupted.
For instance, Ubuntu MATE download page includes SHA256 checksum for every image available there. So, after you downloaded an image, you can generate SHA256 checksum for it and verify if the checksum value matches the one mentioned on the site.
If it doesn’t, that will mean your downloaded image’s integrity is compromised (maybe it was corrupted during the download process). We will use Ubuntu Mate “ubuntu-mate-16.10-desktop-amd64.iso” image file for this guide.

HOW IS CHECKSUM GENERATED?

Checksum is generated by checksum algorithm. Without going into technical details let’s say that it takes a file as input and outputs the checksum value of that file. There are various algorithms for generating checksum. Most popular checksum algorithms are:
  • Secure Hash Algorithms and variants (SHA-1, SHA-2 etc.) and
  • MD5 Algorithm

HOW TO USE CHECKSUM TO VERIFY FILE INTEGRITY [GUI WAY]

If you are looking for graphical solution, you can use GtkHash.
GtkHash is a nifty tool for generating and verifying various checksums. It supports a wide range of checksum algorithms – including SHA, MD5 and others. Here’s a list of supported algorithms:
GtkHash supported Checksum Algorithms

INSTALLING GTKHASH ON UBUNTU

For installing GtkHash on your Ubuntu system, simply run the following command:
sudo apt install gtkhash
That’s it.
GtkHash with UbuntuMATE iso

COMMAND-LINE CHECKSUM TOOLS

Every Linux distribution comes with tools for various checksum algorithms. You can generate and verify checksum with them. The command-line checksum tools are the followings:
  • MD5 checksum tool is called: md5sum
  • SHA-1 checksum tool is called: sha1sum
  • SHA-256 checksum tool is called: sha256sum
There are some more available, e.g.: sha224sum, sha384sum etc. All of them uses similar command formats. Let’s see an example of using sha256sum. We will use the same “ubuntu-mate-16.10-desktop-amd64.iso” image file as we used before.

GENERATING AND VERIFYING SHA256 CHECKSUM WITH SHA256SUM

First go to the directory where the .iso image is stored:
cd ~/itsfoss
Now, for generating SHA256 checksum, enter the following command:
sha256sum ubuntu-mate-16.10-desktop-amd64.iso
You will get the SHA256 checksum in your terminal window! Easy, isn’t it?
Generating SHA256 Checksum for UbuntuMATE iso
If the generated checksum matches with the one provided on the UbuntuMATE download page, that will mean – no data was changed while you downloaded the file or putting otherwise, your downloaded file is not corrupted.
The other mentioned tools work similarly.

HOW ACCURATELY DOES THIS WORK?

If you are wondering, how accurately does these checksum detects corrupted files – if you delete or change even one character from any one of the text files inside the iso image, the checksum algorithm will generate a totally different checksum value for that changed iso image. And that will definitely not match with the checksum provided on the download page.

Comments

Post a Comment

Popular posts from this blog

Changing the keyboard layout RHEL 7

The keyboard layout settings enable the user to control the layout used on the text console and graphical user interfaces. 1.2.1. Displaying the Current Settings As mentioned before, you can check your current keyboard layout configuration with the following command: localectl status In the following output, you can see the keyboard layout configured for the virtual console and for the X11 window system. ~]$  localectl status System Locale: LANG=en_US.utf8 VC Keymap: us X11 Layout: us 1.2.2. Listing Available Keymaps To list all available keyboard layouts that can be configured on your system, type: localectl list-keymaps ⁠ Example 1.5. Searching for a Particular Keymap You can use  grep  to search the output of the previous command for a specific keymap name. There are often multiple keymaps compatible with your currently set locale. For example, to find available Czech keyboard layouts, type: ~]$  ...
Keep reading

HOW TO RECOVER DELETED FILES IN LINUX

Image
Have you ever gotten that horrible feeling? The one you get when you realize that you  accidentally deleted files  and it’s not even in the trash? Often it is immediately preceded by denial: I know I have another copy of it somewhere. But rather than going through all the stages of grief, don’t worry. And remember you’re not alone; sooner or later everyone does this. “Don’t worry?” you counter, “I just erased the only copy of my resume!” No really, don’t worry. All that’s happened is that it’s been bumped off a list. So long as you don’t write onto the drive, it absolutely still exists. In fact, depending on the size of the file and the free space on your drive deleted files can persist indefinitely—even if you do write on the drive. “Yes, fine” you say, “I’ll rest easy knowing my resume ‘exists’ in some abstract sense. But so far as I’m concerned if I can’t open, edit or print from it, it doesn’t exist in any practical sense. What would really help would be a w...
Keep reading

HOW TO INSTALL AND REMOVE SOFTWARE IN UBUNTU

Image
When you  switch to Linux , the experience could be overwhelming at the start. Even the basic things like installing applications in Ubuntu could seem confusing. Don’t worry. Linux provides so many ways to do the same task that it is only natural that you may seem lost, at least in the beginning. You are not alone. We have all been to that stage. In this beginner’s guide, I’ll show most popular ways to install software in Ubuntu. I’ll also show you how to uninstall the software you had installed earlier. I’ll also provide my recommendation about which method you should be using for installing software in Ubuntu. Sit tight and pay attention. This is a long article, a detailed one which is surely going to add to your knowledge. INSTALLING AND UNINSTALLING SOFTWARE IN UBUNTU I am using Ubuntu 16.04 running with Unity desktop environment in this guide. Apart from a couple of screenshots, this guide is applicable to all other flavors of Ubuntu. 1.1 INSTALL SOFTWARE US...
Keep reading