Check your downloads with md5sum - The-Bioinformatics-Group/Albiorix GitHub Wiki

When downloading big files like e.g. raw NGS data from the UPPMAX server, it is recommendable to check if the files you have downloaded are the exact copy of the original or if some interruption in the connection may have corrupted some files. A way to do this is to use the md5 fingerprint that often comes with the data that you want to download. Md5 is used to create a unique fingerprint of a file, which is basically a string consisting of a few dozen characters and digits. This fingerprint is usually stored in a simple text file together with the data-file, usually identified by the file ending ".md5".

This is how a md5 generated fingerprint for file1.fastq may look like:
56857cfc709d3996f057252c16ec4656f5292802 file1.fastq

Now, after you downloaded the data, you can check if md5 creates the same exact fingerprint for your file copy as the one you downloaded with the file. There is an easy automated way to do this using "md5sum".

This is how you check if the downloaded md5-signature is exactly reproduced by md5 for your downloaded file copy: md5sum -c file1.fastq.md5

It will return a positive answer if the fingerprint is correct and you can be sure that your file copy is exactly the same as the original version.