===== Checksum entire folders =====

==== Generate checksum ====

To generate/calculate MD5 checksums for an entire folder, we can do this recursively with find.

<code>find -type f -exec md5sum "{}" + > checksums.txt</code>

This will generate the checksum for every file in the folder and save it to a text file.

Technically, MD5 sums aren't the best anymore but it's fast and nothing we're doing needs security anyways, so it's a good quick sanity check.


**NOTE: I recommend using SHA-256 or SHA-512 over MD5 for anything important.** I have found that SHA-512 is actually faster then SHA-256, so if you have the space, you might as well use it.

<code>find -type f -exec sha512sum "{}" + > checksums.txt</code>


==== Verify checksum ====

To verify that all the files are intact, just make sure it matches.

<code>md5sum -c checksums.txt</code>

This will run through and verify everything is good.

Alternatively, if you used SHA-512, then just replace md5sum with sha512sum.

 <code>sha512sum -c checksums.txt</code>

==== Note on hash functions ====

MD5 is not secure anymore, but I was curious if the speed is a worthwhile tradeoff.

To find out which method is faster, you can use OpenSSL:

<code>openssl speed sha256 sha512 md5</code>

For me, the results are as follows: MD5 > SHA-512 > SHA-256

<code> The 'numbers' are in 1000s of bytes per second processed.
type             16 bytes     64 bytes    256 bytes   1024 bytes   8192 bytes  16384 bytes
md5              84098.48k   196370.90k   361047.62k   459072.69k   496273.01k   495352.10k
sha256           42210.06k    94892.37k   165544.29k   200256.39k   211776.94k   212728.10k
sha512           29820.25k   121823.76k   181359.94k   252842.09k   289037.40k   296808.81k
</code>