How to Check CRC Checksum of Files in Zip Archive on Ubuntu

This guide explains how to verify the integrity of files within a zip archive on Ubuntu using CRC checksums. You will learn the specific commands required to test archives without extracting them, ensuring your data remains uncorrupted during transfer or storage. We will focus on built-in tools available in the standard Linux environment.

Prerequisites

You need the unzip utility installed on your Ubuntu system. It is typically installed by default. If it is missing, install it using the following command:

sudo apt update
sudo apt install unzip

Testing the Archive Integrity

To check the CRC checksum of files inside a zip archive, use the -t flag with the unzip command. This command tests the integrity of the specified zip file without extracting its contents to the disk.

Run the following command in your terminal:

unzip -t archive.zip

Replace archive.zip with the actual name of your file.

Understanding the Output

The terminal will display a list of files contained within the archive. Next to each filename, you will see a status message.

• OK: The CRC checksum matches, and the file is intact.
• bad CRC: The calculated checksum does not match the stored value, indicating data corruption.

At the end of the process, unzip will provide a summary stating whether the test was successful or if errors were found.

Verifying Specific Files

If you only want to check the CRC checksum for specific files within the archive, you can specify their names after the archive name.

unzip -t archive.zip file1.txt file2.jpg

This method allows for quick verification of critical data without processing the entire archive.

Using 7z for Detailed Verification

If you require more detailed output or are handling complex archives, you can use the 7z tool. Install it via sudo apt install p7zip-full. To test the archive, run:

7z t archive.zip

This command performs a similar integrity check and reports the CRC status for every file included in the zip archive.