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

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 | sort -z | xargs -0 sha1sum | sha1sum

And, finally, if you also need to take account of permissions and empty directories:

(find path/to/folder -type f -print0  | sort -z | xargs -0 sha1sum; find path/to/folder \( -type f -o -type d \) -print0 | sort -z | \   xargs -0 stat -c '%n %a') \| sha1sum

The arguments to stat will cause it to print the name of the file, followed by its octal permissions. The two finds will run one after the other, causing double the amount of disk IO, the first finding all file names and checksumming the contents, the second finding all file and directory names, printing name and mode. The list of "file names and checksums", followed by "names and directories, with permissions" will then be checksummed, for a smaller checksum.

• 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

If you just want to check if something in the folder changed, I'd recommend this one:

ls -alR --full-time /folder/of/stuff | sha1sum

It will just give you a hash of the ls output, that contains folders, sub-folders, their files, their timestamp, size and permissions. Pretty much everything that you would need to determine if something has changed.

Please note that this command will not generate hash for each file, but that is why it should be faster than using find.