Idea for a git-like backup program

sha_backup.py

"""
Python script to backup data in src to dst using sha1 hashes of the files
in a backing directory.

Hugh Brown
hughdbrown@yahoo.com
"""

from hashlib import sha1
import os
import os.path
from shutil import copyfile
from subprocess import Popen
from sys import exit

SHA_LEN = 4 # Length of the SHA1 hash to use as directory prefix


def calc_sha(filename, size=10*1000*1000):
    """
    Calculate the sha1 hash of a file. Read in blocks.
    """
    sh = sha1()
    with open(filename, "rb") as f:
        while True:
            s = f.read(size)
            if not s: break
            sh.update(s)
        return sh.hexdigest()


def create_backed_file(filename, backing_root, sha):
    """
    Copy a file to the calculated backing store location.
    """
    dstdir = os.path.join(backing_root, sha[:SHA_LEN])
    if not os.path.exists(dstdir):
        os.makedirs(dstdir)
    dstname = os.path.join(dstdir, sha)
    #print "Copy %s to %s" % (filename, dstname)
    copyfile(filename, dstname)
    return dstname


def calc_dstname(dst_root, filename):
    # FIXME: this assumes relative paths on filename
    return os.path.join(dst_root, filename)


def link_dstfile_to_shafile(dstfile, shafile):
    dstdir = os.path.split(dstfile)[0]
    if not os.path.exists(dstdir):
        print "Create dir %s" % dstdir
        os.makedirs(dstdir)
    args = ["ln", "-sf", shafile, dstfile]
    #print " ".join(args)
    Popen(args)


def sha_file_system(src_iter, dst_root, backing_root):
    for filename in src_iter:
        if os.path.isfile(filename):
            sha = calc_sha(filename)
            backed_file = create_backed_file(filename, backing_root, sha)
            dstfile = calc_dstname(dst_root, filename)
            link_dstfile_to_shafile(dstfile, backed_file)


def walker(dir):
    for root, _, files in os.walk(dir):
        for filename in files:
            yield os.path.join(root, filename)


def get_parser():
    from optparse import OptionParser

    parser = OptionParser()
    parser.add_option("-r", "--recursive", action="store_true", default=False, dest="recursive", help="Recurse directories")
    parser.add_option("-s", "--source", dest="source", default=".", help="Source location")
    parser.add_option("-d", "--destination", dest="destination", default=".", help="Destination location")
    parser.add_option("-b", "--backing", dest="backing", help="Root for backing store")
    return parser


def get_options(parser):
    from glob import glob

    options, args = parser.parse_args()

    if not options.backing:
        print "Require backing_root argument"
        exit(1)
    else:
        backing = os.path.expanduser(options.backing)
        if not os.path.exists(backing):
            print "Create dir %s" % backing
            os.makedirs(backing)
        else:
            assert(os.path.isdir(backing))

    destination = os.path.expanduser(options.destination)

    if options.recursive:
        #source = os.path.expanduser(options.source)
        source = options.source
        fileiter = walker(source)
    else:
        fileiter = (filename for arg in args for filename in glob(arg))

    return fileiter, destination, backing


if __name__ == '__main__':
    fileiter, destination, backing = get_options(get_parser())
    sha_file_system(fileiter, destination, backing)
    exit(0)

I have lots of digital photos and music files and videos that I'd love to copy over to my server and have all the duplicates folded. This is an outline of an idea for doing this.

It's not quite production-ready. It does not take enough care to ensure that the source file does not get overwritten with a link to the sha file.

I have the same problem with photos. I have a one liner I use to find exact duplicates:

find . -type f -print0 | xargs -0 -n1 md5sum | sort -k 1,32 | guniq -w 32 -d --all-repeated=separate | sed -e 's/^[0-9a-f]*\ *//;'