Several changes, see commit details.

blocksync.py

@@ -1,4 +1,4 @@
-#!/usr/bin/env python2
+#!/usr/bin/env python3
 """
 Synchronise block devices over the network
 
@@ -54,14 +54,17 @@
 else:
     USE_NOREUSE = USE_DONTNEED = False
 
-def do_create(f, size):
-    f = open(f, 'a', 0)
+def wrap(x):
+    return ("'%s'" % x)
+
+def do_create(dev, size):
+    f = open(dev, 'wb', 0)
     f.truncate(size)
     f.close()
 
 
-def do_open(f, mode):
-    f = open(f, mode)
+def do_open(dev, mode):
+    f = open(dev, mode)
     if USE_NOREUSE:
         fadvise(f, 0, 0, POSIX_FADV_NOREUSE)
     f.seek(0, 2)
@@ -106,8 +109,19 @@ def server(dev, deleteonexit, options):
     if size > 0:
         do_create(dev, size)
 
-    print(dev, blocksize)
-    f, size = do_open(dev, 'rb+')
+    print(dev)
+    print(blocksize)
+    try:
+        if options.reverse:
+            f, size = do_open(dev, 'rb')
+        else:
+           f, size = do_open(dev, 'rb+')
+
+    except Exception as e:
+        # Error accessing file
+        print("-1")
+        return
+
     print(size)
     sys.stdout.flush()
 
@@ -130,12 +144,16 @@ def server(dev, deleteonexit, options):
         stdout.flush()
         res = stdin.read(COMPLEN)
         if res == DIFF:
-            newblock = stdin.read(blocksize)
-            newblocklen = len(newblock)
-            f.seek(-newblocklen, 1)
-            f.write(newblock)
-            if USE_DONTNEED:
-                fadvise(f, f.tell() - newblocklen, newblocklen, POSIX_FADV_DONTNEED)
+          if options.reverse:
+              stdout.write(block)
+              stdout.flush()
+          else:
+              newblock = stdin.read(blocksize)
+              newblocklen = len(newblock)
+              f.seek(-newblocklen, 1)
+              f.write(newblock)
+              if USE_DONTNEED:
+                  fadvise(f, f.tell() - newblocklen, newblocklen, POSIX_FADV_DONTNEED)
         if i == maxblock:
             break
 
@@ -185,7 +203,10 @@ def sync(workerid, srcdev, dsthost, dstdev, options):
     print("[worker %d] Local fadvise: %s" % (workerid, fadv), file = options.outfile)
 
     try:
-        f, size = do_open(srcdev, 'rb')
+        if options.reverse:
+          f, size = do_open(srcdev, 'rb+')
+      else:
+          f, size = do_open(srcdev, 'rb')
     except Exception as e:
         print("[worker %d] Error accessing source device! %s" % (workerid, e), file = options.outfile)
         sys.exit(1)
@@ -237,12 +258,15 @@ def sync(workerid, srcdev, dsthost, dstdev, options):
         servercmd = 'tmpserver'
         remotescript = copy_self(workerid, cmd)
 
-    cmd += [options.interpreter, remotescript, servercmd, dstdev, '-b', str(blocksize)]
+    cmd += [options.interpreter, remotescript, servercmd, wrap(dstdev), '-b', str(blocksize)]
 
     cmd += ['-d', str(options.fadvise), '-1', options.hash]
     if options.addhash:
         cmd += ['-2', options.addhash]
 
+    if options.reverse:
+        cmd += ['-R']
+
     print("[worker %d] Running: %s" % (workerid, " ".join(cmd[2 if options.passenv and (dsthost != 'localhost') else 0:])), file = options.outfile)
 
     p = subprocess.Popen(cmd, bufsize=0, stdin=subprocess.PIPE, stdout=subprocess.PIPE, close_fds=True)
@@ -257,16 +281,18 @@ def sync(workerid, srcdev, dsthost, dstdev, options):
     fadv = p_out.readline().decode('UTF-8').strip()
     print("[worker %d] Remote fadvise: %s" % (workerid, fadv), file = options.outfile)
 
-    p_in.write(bytes(("%d\n" % (size if options.createdest else 0)).encode("UTF-8")))
+    p_in.write(bytes(("%d\n" % (size if options.createdest and not dryrun else 0)).encode("UTF-8")))
     p_in.flush()
 
-    line = p_out.readline().decode('UTF-8')
+    # line = p_out.readline().decode('UTF-8')
+    a = p_out.readline().decode('UTF-8').strip()
+    b = p_out.readline().decode('UTF-8').strip()
     p.poll()
     if p.returncode is not None:
       print("[worker %d] Failed creating destination file on the remote host!" % workerid, file = options.outfile)
       sys.exit(1)
 
-    a, b = line.split()
+    # a, b = line.split()
     if a != dstdev:
         print("[worker %d] Dest device (%s) doesn't match with the remote host (%s)!" % (workerid, dstdev, a), file = options.outfile)
         sys.exit(1)
@@ -280,6 +306,9 @@ def sync(workerid, srcdev, dsthost, dstdev, options):
         print("[worker %d] Error accessing device on remote host!" % workerid, file = options.outfile)
         sys.exit(1)
     remote_size = int(line)
+    if remote_size < 0:
+        print("[worker %d] Remote device doesn't exists!" % workerid, file = options.outfile)
+        sys.exit(1)
     if size > remote_size:
         print("[worker %d] Source device size (%d) doesn't fit into remote device size (%d)!" % (workerid, size, remote_size), file = options.outfile)
         sys.exit(1)
@@ -317,9 +346,16 @@ def sync(workerid, srcdev, dsthost, dstdev, options):
             else:
                 p_in.write(DIFF)
                 p_in.flush()
-                p_in.write(l_block)
-                p_in.flush()
-
+                if options.reverse:
+                  newblock = p_out.read(blocksize)
+                  newblocklen = len(newblock)
+                  f.seek(-newblocklen, 1)
+                  f.write(newblock)
+                  if USE_DONTNEED:
+                      fadvise(f, f.tell() - newblocklen, newblocklen, POSIX_FADV_DONTNEED)
+              else:
+                  p_in.write(l_block)
+                  p_in.flush()
         if pause_ms:
             time.sleep(pause_ms)
 
@@ -355,16 +391,17 @@ def sync(workerid, srcdev, dsthost, dstdev, options):
     parser.add_option("-2", "--additionalhash", dest = "addhash", help = "second hash used for extra comparison (default is none)")
     parser.add_option("-d", "--fadvise", dest = "fadvise", type = "int", help = "lower cache pressure by using posix_fadivse (requires Python 3 or python-fadvise; 0 = off, 1 = local on, 2 = remote on, 3 = both on; defaults to 3)", default = 3)
     parser.add_option("-p", "--pause", dest = "pause", type="int", help = "pause between processing blocks, reduces system load (ms, defaults to 0)", default = 0)
-    parser.add_option("-c", "--cipher", dest = "cipher", help = "cipher specification for SSH (defaults to blowfish)", default = "blowfish")
-    parser.add_option("-C", "--compress", dest = "compress", action = "store_true", help = "enable compression over SSH (defaults to on)", default = True)
+    parser.add_option("-c", "--cipher", dest = "cipher", help = "cipher specification for SSH (defaults to aes128-ctr)", default = "aes128-ctr")
+    parser.add_option("-N", "--nocompress", dest = "compress", action = "store_false", help = "enable compression over SSH (defaults to on)", default = True)
+    parser.add_option("-R", "--reverse", dest = "reverse", action = "store_true", help = "Remote location to local", default = False)
     parser.add_option("-i", "--id", dest = "keyfile", help = "SSH public key file")
     parser.add_option("-P", "--pass", dest = "passenv", help = "environment variable containing SSH password (requires sshpass)")
     parser.add_option("-s", "--sudo", dest = "sudo", action = "store_true", help = "use sudo on the remote end (defaults to off)", default = False)
     parser.add_option("-x", "--extraparams", dest = "sshparams", help = "additional parameters to pass to SSH")
     parser.add_option("-n", "--dryrun", dest = "dryrun", action = "store_true", help = "do a dry run (don't write anything, just report differences)", default = False)
     parser.add_option("-T", "--createdest", dest = "createdest", action = "store_true", help = "create destination file using truncate(2). Should be safe for subsequent syncs as truncate only modifies the file when the size differs", default = False)
     parser.add_option("-S", "--script", dest = "script", help = "location of script on remote host (otherwise current script is sent over)")
-    parser.add_option("-I", "--interpreter", dest = "interpreter", help = "[full path to] interpreter used to invoke remote server (defaults to python2)", default = "python2")
+    parser.add_option("-I", "--interpreter", dest = "interpreter", help = "[full path to] interpreter used to invoke remote server (defaults to python3)", default = "python3")
     parser.add_option("-t", "--interval", dest = "interval", type = "int", help = "interval between stats output (seconds, defaults to 1)", default = 1)
     parser.add_option("-o", "--output", dest = "outfile", help = "send output to file instead of console")
     parser.add_option("-f", "--force", dest = "force", action= "store_true", help = "force sync and DO NOT ask for confirmation if the destination file already exists")