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It is good to verify the operations when performed, like if you're installing anything from the website, then to verify if it is installed correctly, there must be some checksums.
A popular tool among Linux users is “md5sum” which comes from “MD5” known as the message-digest algorithm. The Md5 consists of a 128-bit cryptographic hash value that is used for the authentication of files and data integrity.
The “md5sum” checksum is a well-suited tool that helps calculate and verify the 128-bit hashes. It is a built-in program in most of the UNIX systems to compute and generate input files for a 128-bit message digest.
The syntax of the “md5sum” command is:
md5sum [option… ] [file… ]The “md5sum” Command Options
The options of the “md5sum” command are mentioned in the given table:
| Option | Description |
|---|---|
| -b | Used for binary mode |
| -c | Used to read MD5 files and check |
| -tag | Used to create BSD style checksum |
| -t | Used for text mode |
| -ignore-missing | To ignore report message for the missing files |
| -quiet | To stop the “ok” message for every successful file |
| -status | To stop displaying output all the time. |
| -strict | Used for improperly formatted checksums |
| -warn | Displays warning message about improperly formatted checksums |
How to Use md5sum Command Options?
Let's do and use some examples to understand the working of the “md5sum” command with options:
Create a text file and write random text in it. Suppose, create a file named “test_file1” and add the following content to it:
Now, execute the following md5sum command to verify the file:
$ md5sum test_file1.txt
Print the generated output in the BSD-style format using the “-tag” option:
$ md5sum --tag test_file1.txt
You can also check the integrity of any other format file. For instance, make a .cpp file and name it “test_file2.cpp” and write any program and save it.
Execute the given command to verify the .cpp file:
$ md5sum test_file2.cpp
Store the value of MD5 in a file and verify it. For this, use mentioned command in the following way to move the value in the MD5 algorithm:
$ md5sum test_file2.cpp > testmd5.md5
The above command will move the value in testmd5.md5 file.
NOTE: The testmd5.md5 is a random name I created, you can change the name according to your choice. Once you run this command, a file will be created in the directory with the mentioned name.
Execute the “-c” option with the md5sum command to check the file's content:
$ md5sum -c testmd5.md5
Similarly, you can also move the standard output of multiple files in the testmd5.md5 to verify the content:
$ md5sum test_file1.txt test_file2.cpp > testmd5.md5
Add some other content in the test_file1 to verify if the MD5 checksum gives the error message. For this, add content in the “test_file1.txt” using “echo”:
$ echo “Hello Linux Writers” >> test_file1.txt
The above command will append “Hello Linux Writers” in the text file.
Now, run the “-check” option to check what output will generate in the terminal after changes have been made:
$ md5sum --check testmd5.md5
The generated output indicates that the content of the files doesn't match.
Use the “-quiet” option to not print the “Ok” message for successfully verified files. It will print the failure result only:
$ md5sum --quiet --check testmd5.md5
Run the “-warn” option to display a message if checksums files are improperly formatted. It will generate a warning message in the terminal:
$ md5sum -c --warn testmd5.md5
Conclusion:
In this guide, we have discussed the “md5sum” command tool that is used to check the 128-bit hashes. We have also checked the data integrity of different files using the “md5sum” command options.
