This article describes the process of verifying AlmaLinux Operating System ISO file for integrity and authenticity. It is very important to check if the ISO file you downloaded is exactly the same as provided by AlmaLinux and it has not been altered during download or in case you got AlmaLinux ISO file from some other third party source. For verifying AlmaLinux ISO file, download the CHECKSUM file given in the download mirror links page.
The Checksum file will contain SHA256 sum values for different AlmaLinux ISO files such as boot.iso, minimal.iso or dvd.iso. You need to verify that the SHA256 sum that you will generate for the downloaded ISO file is same as the SHA256 sum mentioned in the checksum file.
For e.g. the downloaded checksum file shows the SHA256 checksum for Almalinux-8.5-x86_64-dvd.iso ISO file.
So, now you have the ISO file and its SHA256 checksum. Now you need to generate the SHA256 checksum of the downloaded ISO file with the one mentioned in the checksum file. Let us see the method of generating SHA256 checksum on windows and Linux PC and matching them in following three steps:
A. Generate SHA256 checksum on Linux
Open a terminal and change the directory to Downloads folder (or location where you have kept AlmaLinux ISO file). Run the sha256sum -b [AlmaLinux ISO file name] command as shown in below image (Arrow pointer-1).
The output of the sha256sum command will be the SHA256 checksum for the downloaded AlmaLinux ISO file (Arrow pointer-2). For e.g. the sha256sum generated in the above image is 54b8881bebd924e4699ed12634187a82156fdb0fa57ec24058d04d70d2f033b3.
B. Generate SHA256 checksum on Windows
Open a Windows PowerShell and change the directory to Downloads folder (or location where you have kept AlmaLinux ISO file). Run the CertUtil -hashfile [AlmaLinux ISO file name] SHA256 command as shown in below image (Arrow pointer-1).
The output of the CertUtil command will be the SHA256 checksum for the downloaded AlmaLinux ISO file (Arrow pointer-2). For e.g. the sha256sum generated in the above image is 54b8881bebd924e4699ed12634187a82156fdb0fa57ec24058d04d70d2f033b3.
C. Match SHA256 checksum
Match the generated sha256 checksum with the checksum mentioned in the check sum file. If both these checksum match, then the AlmaLinux ISO file is intact as officially provided by AlmaLinux. You may match the checksums manually or may paste both checksums in MS excel or Libre Calc and using ‘=’ operator to match the checksums.
Paste both the checksums in two different cells and use ‘=’ operator to compare the values.
If the ‘equals’ operator results in “True” then the checksums are matched.
You can proceed to create AlmaLinux bootable USB with the ISO file upon successful verification. If verification fails, re-download the ISO file from authentic source.
Note: This article is a part of AlmaLinux – The Complete Installation Guide series. You need to visit previous (AlmaLinux ISO download process) and next chapters to understand the topic in entirety.
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