[linux} How to compute and verify file checksum


        
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            Compute SHA message digest of a file to verify that its contents have not been altered.
You have two possible ways to perform this operation. 

use single shasum Perl script provided by the perl package, or;
sha1sum/sha224sum/sha256sum/sha384sum/sha512sum commands provided by the coreutils package.


coreutils utilities
coreutils package provides multiple commands to compute and verify file checksums depending on the used algorithm.

sha1sum command to use SHA-1

sha224sum command to use SHA-224 algorithm 
sha256sum command to use SHA-256 algorithm
sha384sum command to use SHA-384 algorithm
sha512sum command to use SHA-512 algorithm.

Compute checksum for debian-stretch.tar file using SHA-256 algorithm.
$ sha256sum debian-stretch.tar | tee debian-stretch.tar.sha256sum 
cc59e9182464ffe338a0addd5ae2ffaa062047a87f3c78b4eca8c590fd60c67e  debian-stretch.tar
Verify checksum for file or files defined in debian-stretch.tar.sha256sum file.
$ sha256sum --check debian-stretch.tar.sha256sum 
debian-stretch.tar: OK
Failed checksum can be easily spotted and identified.
$ sha256sum --check debian-stretch.tar.sha256sum 
debian-stretch.tar: FAILED
sha256sum: WARNING: 1 computed checksum did NOT match

perl utilities
perl package provides shasum command to compute and verify file checksums. You can use it as a replacement for coreutils alternatives as it mimics behavior of the equivalent GNU utilities.
Compute checksum for debian-stretch.tar file using SHA-256 algorithm.
$ shasum --algorithm 256 debian-stretch.tar | tee debian-stretch.tar.sha256sum
cc59e9182464ffe338a0addd5ae2ffaa062047a87f3c78b4eca8c590fd60c67e  debian-stretch.tar
Verify checksum for file or files defined in debian-stretch.tar.sha256sum file.
$ shasum --algorithm 256 --check debian-stretch.tar.sha256sum 
debian-stretch.tar: OK
You do not need to specify algorithm when using regular ones, but it does not apply to SHA-512/224 and SHA-512/256 algorithms.
$ shasum --check debian-stretch.tar.sha256sum 
debian-stretch.tar: OK
Failed checksum can be easily spotted and identified.
$ shasum --algorithm 256 --check debian-stretch.tar.sha256sum 
debian-stretch.tar: FAILED
shasum: WARNING: 1 computed checksum did NOT match
You can use default SHA-1 1 algorithm to verify file integrity or SHA-2 family algorithms like SHA-224 224, SHA-256 256, SHA-384 384, SHA-512 512. Additionally you can take adavantage of the most recent members of the SHA-2 family like SHA-512/224 512224 and SHA-512/256 512256.
Source: https://blog.sleeplessbeastie.eu/2018/07/23/how-to-compute-and-verify-file-checksum/