Can you use OpenSSL to generate an md5 or sha hash on a directory of files?

Question

I'm interested in storing an indicator of file / directory integrity between two archived copies of directories. It's around 1TB of data stored recursively on hard drives. Is there a way using OpenSSL to generate a single hash for all the files that can be used as a comparison between two copies of the data, or at a later point to verify the data has not changed?

Answer 1

You could recursively generate all the hashes, concatenate the hashes into a single file, then generate a hash of that file.

Answer 2

You can't do a cumulative hash of them all to make a single hash, but you can compress them first then compute the hash:

$tar -czpf archive1.tar.gz folder1/
$tar -czpf archive2.tar.gz folder2/
$openssl md5 archive1.tar.gz archive2.tar.gz

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to recursively hash each file:

$find . -type f -exec openssl md5 {} +

Answer 3

Doing a md5 sum on the tar would never work unless all of the metadata (creation date, etc.) was identical as well, because tar stores that as part of its archive.

I would probably do an md5 sum of the contents of all of the files:

find folder1 -type f | sort | tr '\n' '\0' | xargs -0 cat | openssl md5
find folder2 -type f | sort | tr '\n' '\0' | xargs -0 cat | openssl md5

Answer 4

http://akiscode.com/articles/sha-1directoryhash.shtml