Block device sync between remote hosts. Based off http://www.bouncybouncy.net/programs/blocksync.py

blocksync.py

#!/usr/bin/env python
"""
Synchronise block devices over the network
 
Copyright 2006-2008 Justin Azoff <[email protected]>
Copyright 2011 Robert Coup <[email protected]>
License: GPL
 
Getting started:
 
* Copy blocksync.py to the home directory on the remote host
* Make sure your remote user can either sudo or is root itself.
* Make sure your local user can ssh to the remote host
* Invoke:
    sudo python blocksync.py /dev/source user@remotehost /dev/dest
"""
 
import sys
from sha import sha
import subprocess
import time
 
SAME = "same\n"
DIFF = "diff\n"
 
 
def do_open(f, mode):
    f = open(f, mode)
    f.seek(0, 2)
    size = f.tell()
    f.seek(0)
    return f, size
 
 
def getblocks(f, blocksize):
    while 1:
        block = f.read(blocksize)
        if not block:
            break
        yield block
 
 
def server(dev, blocksize):
    print dev, blocksize
    f, size = do_open(dev, 'r+')
    print size
    sys.stdout.flush()
 
    for block in getblocks(f, blocksize):
        print sha(block).hexdigest()
        sys.stdout.flush()
        res = sys.stdin.readline()
        if res != SAME:
            newblock = sys.stdin.read(blocksize)
            f.seek(-len(newblock), 1)
            f.write(newblock)
 
 
def sync(srcdev, dsthost, dstdev=None, blocksize=1024 * 1024):
 
    if not dstdev:
        dstdev = srcdev
 
    print "Block size is %0.1f MB" % (float(blocksize) / (1024 * 1024))
    # cmd = ['ssh', '-c', 'blowfish', dsthost, 'sudo', 'python', 'blocksync.py', 'server', dstdev, '-b', str(blocksize)]
    cmd = ['ssh', '-c', 'blowfish', dsthost, 'python', 'blocksync.py', 'server', dstdev, '-b', str(blocksize)]
    print "Running: %s" % " ".join(cmd)
 
    p = subprocess.Popen(cmd, bufsize=0, stdin=subprocess.PIPE, stdout=subprocess.PIPE, close_fds=True)
    p_in, p_out = p.stdin, p.stdout
 
    line = p_out.readline()
    p.poll()
    if p.returncode is not None:
        print "Error connecting to or invoking blocksync on the remote host!"
        sys.exit(1)
 
    a, b = line.split()
    if a != dstdev:
        print "Dest device (%s) doesn't match with the remote host (%s)!" % (dstdev, a)
        sys.exit(1)
    if int(b) != blocksize:
        print "Source block size (%d) doesn't match with the remote host (%d)!" % (blocksize, int(b))
        sys.exit(1)
 
    try:
        f, size = do_open(srcdev, 'r')
    except Exception, e:
        print "Error accessing source device! %s" % e
        sys.exit(1)
 
    line = p_out.readline()
    p.poll()
    if p.returncode is not None:
        print "Error accessing device on remote host!"
        sys.exit(1)
    remote_size = int(line)
    if size != remote_size:
        print "Source device size (%d) doesn't match remote device size (%d)!" % (size, remote_size)
        sys.exit(1)
 
    same_blocks = diff_blocks = 0
 
    print "Starting sync..."
    t0 = time.time()
    t_last = t0
    size_blocks = size / blocksize
    for i, l_block in enumerate(getblocks(f, blocksize)):
        l_sum = sha(l_block).hexdigest()
        r_sum = p_out.readline().strip()
 
        if l_sum == r_sum:
            p_in.write(SAME)
            p_in.flush()
            same_blocks += 1
        else:
            p_in.write(DIFF)
            p_in.flush()
            p_in.write(l_block)
            p_in.flush()
            diff_blocks += 1
 
        t1 = time.time()
        if t1 - t_last > 1 or (same_blocks + diff_blocks) >= size_blocks:
            rate = (i + 1.0) * blocksize / (1024.0 * 1024.0) / (t1 - t0)
            print "\rsame: %d, diff: %d, %d/%d, %5.1f MB/s" % (same_blocks, diff_blocks, same_blocks + diff_blocks, size_blocks, rate),
            t_last = t1
 
    print "\n\nCompleted in %d seconds" % (time.time() - t0)
 
    return same_blocks, diff_blocks
 
if __name__ == "__main__":
    from optparse import OptionParser
    parser = OptionParser(usage="%prog [options] /dev/source user@remotehost [/dev/dest]")
    parser.add_option("-b", "--blocksize", dest="blocksize", action="store", type="int", help="block size (bytes)", default=1024 * 1024)
    (options, args) = parser.parse_args()
 
    if len(args) < 2:
        parser.print_help()
        print __doc__
        sys.exit(1)
 
    if args[0] == 'server':
        dstdev = args[1]
        server(dstdev, options.blocksize)
    else:
        srcdev = args[0]
        dsthost = args[1]
        if len(args) > 2:
            dstdev = args[2]
        else:
            dstdev = None
        sync(srcdev, dsthost, dstdev, options.blocksize)

Hi there,
I would like to incorporate the changes from slesru on Apr 21, 2014 to make it possible to reverse the direction (in order to firewall off access to my backups and pull from the live server instead). However, it seems the code has changed a little since 2014, and I'm not sure how to adapt the changes. I'll have a crack at it and run some tests, but if anyone can help out with any code/suggestions it would help me a lot.