Linux: compute a single hash for a given folder & contents?

Surely there must be a way to do this easily!

I've tried the linux command-line apps sha1sum & md5sum but they seem only to be able to compute hashes of individual files and output a list of hash values, one for each file.

I need to generate a single hash for the entire contents of a folder (not just the filenames).

I'd like to do something like

sha1sum /folder/of/stuff > singlehashvalue

Edit: to clarify, my files are at multiple levels in a directory tree, they're not all sitting in the same root folder.

From stackoverflow

• If you just want to hash the contents of the files, ignoring the filenames then you can use

  cat $FILES | md5sum
  

  Make sure you have the files in the same order when computing the hash:

  cat $(echo $FILES | sort) | md5sum
  

  But you can't have directories in your list of files.

• Try to make it in two steps:

  1. create a file with hashes for all files in a folder
  2. hash this file

  Like so:

  # for FILE in `find /folder/of/stuff -type f | sort`; do sha1sum $FILE >> hashes; done
  # sha1sum hashes
  

  Or do it all at once:

  # cat `find /folder/of/stuff -type f | sort` | sha1sum
  

• You could sha1sum to generate the list of hash values and then sha1sum that list again, it depends on what exactly it is you want to accomplish.

• I would pipe the results for individual files through sort (to prevent a mere reordering of files to change the hash) into md5sum or sha1sum, whichever you choose.

• One possible way would be:

  sha1sum /path/to/folder/* | sha1sum
  

  If there is a whole directory tree, you're probably better off using find and xargs. One possible command would be

  find /path/to/folder -type f -print0 | xargs -0 sha1sum | sha1sum
  

  Edit: Good point, it's probably a good thing to sort the list of files, so:

  find path/to/folder -type f -print0 | sort -z | xargs -0 sha1sum | sha1sum
  

  Rafał Dowgird : If you sort after the first sha1sum, then a LF in a filename should do no harm.

  Aaron Digulla : Edited. Sort can work on 0 delimited lists with the -z option.

  David Schmitt : and don't forget to set LC_ALL=POSIX, so the various tools create locale independent output.

• • Commit the directory to git, use the commit hash. See metastore for a way to also control permissions.

  • Use a file system intrusion detection tool like aide.

  • hash a tar ball of the directory:

    tar cvf - /path/to/folder | sha1sum

  • Code something yourself, like vatine's oneliner:

    find /path/to/folder -type f -print0 | sort -z | xargs -0 sha1sum | sha1sum

  Bombe : +1 for the Git solution. :)

• What's wrong with a tar -c /path/to/folder | sha1sum?