Refactor cumulus-util into a library plus small command front-end.
authorMichael Vrable <mvrable@google.com>
Thu, 20 Sep 2012 20:43:22 +0000 (13:43 -0700)
committerMichael Vrable <mvrable@google.com>
Tue, 25 Sep 2012 21:50:28 +0000 (14:50 -0700)
There is still more cleanup work to be done here, but this first step
makes commands in cumulus-util importable as a Python module for re-use
elsewhere.

cumulus-util
python/cumulus/cmd_util.py [new file with mode: 0644]

index 1608b63..e8bdf5e 100755 (executable)
 #
 # Utility for managing Cumulus archives.
 
-import getpass, os, stat, sys, time
-from optparse import OptionParser
+import os, sys
 
 # Automatically set Python path, based on script directory.  This should be
 # removed if the tools are properly installed somewhere.
 script_directory = os.path.dirname(sys.argv[0])
 sys.path.append(os.path.join(script_directory, 'python'))
 
-import cumulus
+import cumulus.cmd_util
 
-# We support up to "Cumulus Snapshot v0.11" formats, but are also limited by
-# the cumulus module.
-FORMAT_VERSION = min(cumulus.FORMAT_VERSION, (0, 11))
-
-def check_version(format):
-    ver = cumulus.parse_metadata_version(format)
-    if ver > FORMAT_VERSION:
-        raise RuntimeError("Unsupported Cumulus format: " + format)
-
-# Read a passphrase from the user and store it in the LBS_GPG_PASSPHRASE
-# environment variable.
-def get_passphrase():
-    ENV_KEY = 'LBS_GPG_PASSPHRASE'
-    if not os.environ.has_key(ENV_KEY):
-        os.environ[ENV_KEY] = getpass.getpass()
-
-def cmd_prune_db(args):
-    """ Delete old snapshots from the local database, though do not
-        actually schedule any segment cleaning.
-        Syntax: $0 --localdb=LOCALDB prune-db
-    """
-    db = cumulus.LocalDatabase(options.localdb)
-
-    # Delete old snapshots from the local database.
-    #db.garbage_collect()
-    #db.commit()
-
-def cmd_clean(args, clean_threshold=7.0):
-    """ Run the segment cleaner.
-        Syntax: $0 --localdb=LOCALDB clean
-    """
-    db = cumulus.LocalDatabase(options.localdb)
-
-    # Delete old snapshots from the local database.
-    intent = float(options.intent)
-    for s in db.list_schemes():
-        db.garbage_collect(s, intent)
-
-    # Expire segments which are poorly-utilized.
-    for s in db.get_segment_cleaning_list():
-        if s.cleaning_benefit > clean_threshold:
-            print "Cleaning segment %d (benefit %.2f)" % (s.id,
-                                                          s.cleaning_benefit)
-            db.mark_segment_expired(s)
-        else:
-            break
-    db.balance_expired_objects()
-    db.commit()
-
-def cmd_list_snapshots(args):
-    """ List snapshots stored.
-        Syntax: $0 --data=DATADIR list-snapshots
-    """
-    store = cumulus.LowlevelDataStore(options.store)
-    for s in sorted(store.list_snapshots()):
-        print s
-
-def cmd_list_snapshot_sizes(args):
-    """ List size of data needed for each snapshot.
-        Syntax: $0 --data=DATADIR list-snapshot-sizes
-    """
-    lowlevel = cumulus.LowlevelDataStore(options.store)
-    lowlevel.scan()
-    store = cumulus.ObjectStore(lowlevel)
-    previous = set()
-    exts = {}
-    for seg in lowlevel.store.list('segments'):
-        exts.update ([seg.split ('.', 1)])
-    for s in sorted(lowlevel.list_snapshots()):
-        d = cumulus.parse_full(store.load_snapshot(s))
-        check_version(d['Format'])
-
-        try:
-            intent = float(d['Backup-Intent'])
-        except:
-            intent = 1.0
-
-        segments = d['Segments'].split()
-        (size, added, removed, addcount, remcount) = (0, 0, 0, 0, 0)
-        lo_stat = lowlevel.lowlevel_stat
-        for seg in segments:
-            segsize = lo_stat('.'.join ((seg, exts[seg])))['size']
-            size += segsize
-            if seg not in previous:
-                added += segsize
-                addcount += 1
-        for seg in previous:
-            if seg not in segments:
-                removed += lo_stat('.'.join((seg, exts[seg])))['size']
-                remcount += 1
-        previous = set(segments)
-        print "%s [%s]: %.3f +%.3f -%.3f (+%d/-%d segments)" % (s, intent, size / 1024.0**2, added / 1024.0**2, removed / 1024.0**2, addcount, remcount)
-
-def cmd_garbage_collect(args):
-    """ Search for any files which are not needed by any current
-        snapshots and offer to delete them.
-        Syntax: $0 --store=DATADIR gc
-    """
-    lowlevel = cumulus.LowlevelDataStore(options.store)
-    lowlevel.scan()
-    store = cumulus.ObjectStore(lowlevel)
-    snapshots = set(lowlevel.list_snapshots())
-    segments = set()
-    for s in snapshots:
-        d = cumulus.parse_full(store.load_snapshot(s))
-        check_version(d['Format'])
-        segments.update(d['Segments'].split())
-
-    referenced = snapshots.union(segments)
-    reclaimed = 0
-    for (t, r) in cumulus.store.type_patterns.items():
-        for f in lowlevel.store.list(t):
-            m = r.match(f)
-            if m is None or m.group(1) not in referenced:
-                print "Garbage:", (t, f)
-                reclaimed += lowlevel.store.stat(t, f)['size']
-                if not options.dry_run:
-                    lowlevel.store.delete(t, f)
-    print "Reclaimed space:", reclaimed
-
-cmd_gc = cmd_garbage_collect
-
-def cmd_object_checksums(segments):
-    """ Build checksum list for objects in the given segments, or all
-        segments if none are specified.
-    """
-    get_passphrase()
-    lowlevel = cumulus.LowlevelDataStore(options.store)
-    store = cumulus.ObjectStore(lowlevel)
-    if len(segments) == 0:
-        segments = sorted(lowlevel.list_segments())
-    for s in segments:
-        for (o, data) in store.load_segment(s):
-            csum = cumulus.ChecksumCreator().update(data).compute()
-            print "%s/%s:%d:%s" % (s, o, len(data), csum)
-    store.cleanup()
-object_sums = cmd_object_checksums
-
-def cmd_read_snapshots(snapshots):
-    """ Read a snapshot file
-    """
-    get_passphrase()
-    lowlevel = cumulus.LowlevelDataStore(options.store)
-    store = cumulus.ObjectStore(lowlevel)
-    for s in snapshots:
-        d = cumulus.parse_full(store.load_snapshot(s))
-        check_version(d['Format'])
-        print d
-        print d['Segments'].split()
-    store.cleanup()
-
-def cmd_read_metadata(args):
-    """ Produce a flattened metadata dump from a snapshot
-    """
-    snapshot = args [0]
-    get_passphrase()
-    lowlevel = cumulus.LowlevelDataStore(options.store)
-    store = cumulus.ObjectStore(lowlevel)
-    d = cumulus.parse_full(store.load_snapshot(snapshot))
-    check_version(d['Format'])
-    metadata = cumulus.read_metadata(store, d['Root'])
-    blank = True
-    for l in metadata:
-        if l == '\n':
-            if blank: continue
-            blank = True
-        else:
-            blank = False
-        sys.stdout.write(l)
-    store.cleanup()
-
-def cmd_verify_snapshots(snapshots):
-    """ Verify snapshot integrity
-    """
-    get_passphrase()
-    lowlevel = cumulus.LowlevelDataStore(options.store)
-    store = cumulus.ObjectStore(lowlevel)
-    for s in snapshots:
-        cumulus.accessed_segments.clear()
-        print "#### Snapshot", s
-        d = cumulus.parse_full(store.load_snapshot(s))
-        check_version(d['Format'])
-        print "## Root:", d['Root']
-        metadata = cumulus.iterate_metadata(store, d['Root'])
-        for m in metadata:
-            if m.fields['type'] not in ('-', 'f'): continue
-            print "%s [%d bytes]" % (m.fields['name'], int(m.fields['size']))
-            verifier = cumulus.ChecksumVerifier(m.fields['checksum'])
-            size = 0
-            for block in m.data():
-                data = store.get(block)
-                verifier.update(data)
-                size += len(data)
-            if int(m.fields['size']) != size:
-                raise ValueError("File size does not match!")
-            if not verifier.valid():
-                raise ValueError("Bad checksum found")
-
-        # Verify that the list of segments included with the snapshot was
-        # actually accurate: covered all segments that were really read, and
-        # doesn't contain duplicates.
-        listed_segments = set(d['Segments'].split())
-        if cumulus.accessed_segments - listed_segments:
-            print "Error: Some segments not listed in descriptor!"
-            print sorted(list(cumulus.accessed_segments - listed_segments))
-        if listed_segments - cumulus.accessed_segments :
-            print "Warning: Extra unused segments listed in descriptor!"
-            print sorted(list(listed_segments - cumulus.accessed_segments))
-    store.cleanup()
-
-def cmd_restore_snapshot(args):
-    """ Restore a snapshot, or some subset of files from it
-    """
-    get_passphrase()
-    lowlevel = cumulus.LowlevelDataStore(options.store)
-    store = cumulus.ObjectStore(lowlevel)
-    snapshot = cumulus.parse_full(store.load_snapshot(args[0]))
-    check_version(snapshot['Format'])
-    destdir = args[1]
-    paths = args[2:]
-
-    def matchpath(path):
-        "Return true if the specified path should be included in the restore."
-
-        # No specification of what to restore => restore everything
-        if len(paths) == 0: return True
-
-        for p in paths:
-            if path == p: return True
-            if path.startswith(p + "/"): return True
-        return False
-
-    def warn(m, msg):
-        print "Warning: %s: %s" % (m.items.name, msg)
-
-    # Phase 1: Read the complete metadata log and create directory structure.
-    metadata_items = []
-    metadata_paths = {}
-    metadata_segments = {}
-    for m in cumulus.iterate_metadata(store, snapshot['Root']):
-        pathname = os.path.normpath(m.items.name)
-        while os.path.isabs(pathname):
-            pathname = pathname[1:]
-        if not matchpath(pathname): continue
-
-        destpath = os.path.join(destdir, pathname)
-        if m.items.type == 'd':
-            path = destpath
-        else:
-            (path, filename) = os.path.split(destpath)
-
-        metadata_items.append((pathname, m))
-        if m.items.type in ('-', 'f'):
-            metadata_paths[pathname] = m
-            for block in m.data():
-                (segment, object, checksum, slice) \
-                    = cumulus.ObjectStore.parse_ref(block)
-                if segment not in metadata_segments:
-                    metadata_segments[segment] = set()
-                metadata_segments[segment].add(pathname)
-
-        try:
-            if not os.path.isdir(path):
-                print "mkdir:", path
-                os.makedirs(path)
-        except Exception, e:
-            warn(m, "Error creating directory structure: %s" % (e,))
-            continue
-
-    # Phase 2: Restore files, ordered by how data is stored in segments.
-    def restore_file(pathname, m):
-        assert m.items.type in ('-', 'f')
-        print "extract:", pathname
-        destpath = os.path.join(destdir, pathname)
-
-        file = open(destpath, 'wb')
-        verifier = cumulus.ChecksumVerifier(m.items.checksum)
-        size = 0
-        for block in m.data():
-            data = store.get(block)
-            verifier.update(data)
-            size += len(data)
-            file.write(data)
-        file.close()
-        if int(m.fields['size']) != size:
-            raise ValueError("File size does not match!")
-        if not verifier.valid():
-            raise ValueError("Bad checksum found")
-
-    while metadata_segments:
-        (segment, items) = metadata_segments.popitem()
-        print "+ Segment", segment
-        for pathname in sorted(items):
-            if pathname in metadata_paths:
-                restore_file(pathname, metadata_paths[pathname])
-                del metadata_paths[pathname]
-
-    print "+ Remaining files"
-    while metadata_paths:
-        (pathname, m) = metadata_paths.popitem()
-        restore_file(pathname, m)
-
-    # Phase 3: Restore special files (symlinks, devices).
-    # Phase 4: Restore directory permissions and modification times.
-    for (pathname, m) in reversed(metadata_items):
-        print "permissions:", pathname
-        destpath = os.path.join(destdir, pathname)
-        (path, filename) = os.path.split(destpath)
-
-        # TODO: Check for ../../../paths that might attempt to write outside
-        # the destination directory.  Maybe also check attempts to follow
-        # symlinks pointing outside?
-
-        try:
-            if m.items.type in ('-', 'f', 'd'):
-                pass
-            elif m.items.type == 'l':
-                try:
-                    target = m.items.target
-                except:
-                    # Old (v0.2 format) name for 'target'
-                    target = m.items.contents
-                os.symlink(target, destpath)
-            elif m.items.type == 'p':
-                os.mkfifo(destpath)
-            elif m.items.type in ('c', 'b'):
-                if m.items.type == 'c':
-                    mode = 0600 | stat.S_IFCHR
-                else:
-                    mode = 0600 | stat.S_IFBLK
-                os.mknod(destpath, mode, os.makedev(*m.items.device))
-            elif m.items.type == 's':
-                pass        # TODO: Implement
-            else:
-                warn(m, "Unknown type code: " + m.items.type)
-                continue
-
-        except Exception, e:
-            warn(m, "Error restoring: %s" % (e,))
-            continue
-
-        try:
-            uid = m.items.user[0]
-            gid = m.items.group[0]
-            os.lchown(destpath, uid, gid)
-        except Exception, e:
-            warn(m, "Error restoring file ownership: %s" % (e,))
-
-        if m.items.type == 'l':
-            continue
-
-        try:
-            os.chmod(destpath, m.items.mode)
-        except Exception, e:
-            warn(m, "Error restoring file permissions: %s" % (e,))
-
-        try:
-            os.utime(destpath, (time.time(), m.items.mtime))
-        except Exception, e:
-            warn(m, "Error restoring file timestamps: %s" % (e,))
-
-    store.cleanup()
-
-usage = ["%prog [option]... command [arg]...", "", "Commands:"]
-cmd = method = None
-for cmd, method in locals().iteritems():
-    if cmd.startswith ('cmd_'):
-        usage.append(cmd[4:].replace('_', '-') + ':' + method.__doc__)
-parser = OptionParser(usage="\n".join(usage))
-parser.add_option("-v", action="store_true", dest="verbose", default=False,
-                  help="increase verbosity")
-parser.add_option("-n", action="store_true", dest="dry_run", default=False,
-                  help="dry run")
-parser.add_option("--store", dest="store",
-                  help="specify path to backup data store")
-parser.add_option("--localdb", dest="localdb",
-                  help="specify path to local database")
-parser.add_option("--intent", dest="intent", default=1.0,
-                  help="give expected next snapshot type when cleaning")
-(options, args) = parser.parse_args(sys.argv[1:])
-
-if len(args) == 0:
-    parser.print_usage()
-    sys.exit(1)
-cmd = args[0]
-args = args[1:]
-method = locals().get('cmd_' + cmd.replace('-', '_'))
-if method:
-    method (args)
-else:
-    print "Unknown command:", cmd
-    parser.print_usage()
-    sys.exit(1)
+cumulus.cmd_util.main(sys.argv)
diff --git a/python/cumulus/cmd_util.py b/python/cumulus/cmd_util.py
new file mode 100644 (file)
index 0000000..c3733f0
--- /dev/null
@@ -0,0 +1,422 @@
+# Cumulus: Smart Filesystem Backup to Dumb Servers
+#
+# Copyright (C) 2006-2009  The Regents of the University of California
+# Copyright (C) 2012  Google Inc.
+# Written by Michael Vrable <mvrable@cs.ucsd.edu>
+#
+# This program is free software; you can redistribute it and/or modify
+# it under the terms of the GNU General Public License as published by
+# the Free Software Foundation; either version 2 of the License, or
+# (at your option) any later version.
+#
+# This program is distributed in the hope that it will be useful,
+# but WITHOUT ANY WARRANTY; without even the implied warranty of
+# MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+# GNU General Public License for more details.
+#
+# You should have received a copy of the GNU General Public License along
+# with this program; if not, write to the Free Software Foundation, Inc.,
+# 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301 USA.
+
+"""Implementation of the Cumulus command-line utility program."""
+
+import getpass, os, stat, sys, time
+from optparse import OptionParser
+
+import cumulus
+
+# We support up to "Cumulus Snapshot v0.11" formats, but are also limited by
+# the cumulus module.
+FORMAT_VERSION = min(cumulus.FORMAT_VERSION, (0, 11))
+
+def check_version(format):
+    ver = cumulus.parse_metadata_version(format)
+    if ver > FORMAT_VERSION:
+        raise RuntimeError("Unsupported Cumulus format: " + format)
+
+# Read a passphrase from the user and store it in the LBS_GPG_PASSPHRASE
+# environment variable.
+def get_passphrase():
+    ENV_KEY = 'LBS_GPG_PASSPHRASE'
+    if not os.environ.has_key(ENV_KEY):
+        os.environ[ENV_KEY] = getpass.getpass()
+
+def cmd_prune_db(args):
+    """ Delete old snapshots from the local database, though do not
+        actually schedule any segment cleaning.
+        Syntax: $0 --localdb=LOCALDB prune-db
+    """
+    db = cumulus.LocalDatabase(options.localdb)
+
+    # Delete old snapshots from the local database.
+    #db.garbage_collect()
+    #db.commit()
+
+def cmd_clean(args, clean_threshold=7.0):
+    """ Run the segment cleaner.
+        Syntax: $0 --localdb=LOCALDB clean
+    """
+    db = cumulus.LocalDatabase(options.localdb)
+
+    # Delete old snapshots from the local database.
+    intent = float(options.intent)
+    for s in db.list_schemes():
+        db.garbage_collect(s, intent)
+
+    # Expire segments which are poorly-utilized.
+    for s in db.get_segment_cleaning_list():
+        if s.cleaning_benefit > clean_threshold:
+            print "Cleaning segment %d (benefit %.2f)" % (s.id,
+                                                          s.cleaning_benefit)
+            db.mark_segment_expired(s)
+        else:
+            break
+    db.balance_expired_objects()
+    db.commit()
+
+def cmd_list_snapshots(args):
+    """ List snapshots stored.
+        Syntax: $0 --data=DATADIR list-snapshots
+    """
+    store = cumulus.LowlevelDataStore(options.store)
+    for s in sorted(store.list_snapshots()):
+        print s
+
+def cmd_list_snapshot_sizes(args):
+    """ List size of data needed for each snapshot.
+        Syntax: $0 --data=DATADIR list-snapshot-sizes
+    """
+    lowlevel = cumulus.LowlevelDataStore(options.store)
+    lowlevel.scan()
+    store = cumulus.ObjectStore(lowlevel)
+    previous = set()
+    exts = {}
+    for seg in lowlevel.store.list('segments'):
+        exts.update ([seg.split ('.', 1)])
+    for s in sorted(lowlevel.list_snapshots()):
+        d = cumulus.parse_full(store.load_snapshot(s))
+        check_version(d['Format'])
+
+        try:
+            intent = float(d['Backup-Intent'])
+        except:
+            intent = 1.0
+
+        segments = d['Segments'].split()
+        (size, added, removed, addcount, remcount) = (0, 0, 0, 0, 0)
+        lo_stat = lowlevel.lowlevel_stat
+        for seg in segments:
+            segsize = lo_stat('.'.join ((seg, exts[seg])))['size']
+            size += segsize
+            if seg not in previous:
+                added += segsize
+                addcount += 1
+        for seg in previous:
+            if seg not in segments:
+                removed += lo_stat('.'.join((seg, exts[seg])))['size']
+                remcount += 1
+        previous = set(segments)
+        print "%s [%s]: %.3f +%.3f -%.3f (+%d/-%d segments)" % (s, intent, size / 1024.0**2, added / 1024.0**2, removed / 1024.0**2, addcount, remcount)
+
+def cmd_garbage_collect(args):
+    """ Search for any files which are not needed by any current
+        snapshots and offer to delete them.
+        Syntax: $0 --store=DATADIR gc
+    """
+    lowlevel = cumulus.LowlevelDataStore(options.store)
+    lowlevel.scan()
+    store = cumulus.ObjectStore(lowlevel)
+    snapshots = set(lowlevel.list_snapshots())
+    segments = set()
+    for s in snapshots:
+        d = cumulus.parse_full(store.load_snapshot(s))
+        check_version(d['Format'])
+        segments.update(d['Segments'].split())
+
+    referenced = snapshots.union(segments)
+    reclaimed = 0
+    for (t, r) in cumulus.store.type_patterns.items():
+        for f in lowlevel.store.list(t):
+            m = r.match(f)
+            if m is None or m.group(1) not in referenced:
+                print "Garbage:", (t, f)
+                reclaimed += lowlevel.store.stat(t, f)['size']
+                if not options.dry_run:
+                    lowlevel.store.delete(t, f)
+    print "Reclaimed space:", reclaimed
+
+cmd_gc = cmd_garbage_collect
+
+def cmd_object_checksums(segments):
+    """ Build checksum list for objects in the given segments, or all
+        segments if none are specified.
+    """
+    get_passphrase()
+    lowlevel = cumulus.LowlevelDataStore(options.store)
+    store = cumulus.ObjectStore(lowlevel)
+    if len(segments) == 0:
+        segments = sorted(lowlevel.list_segments())
+    for s in segments:
+        for (o, data) in store.load_segment(s):
+            csum = cumulus.ChecksumCreator().update(data).compute()
+            print "%s/%s:%d:%s" % (s, o, len(data), csum)
+    store.cleanup()
+object_sums = cmd_object_checksums
+
+def cmd_read_snapshots(snapshots):
+    """ Read a snapshot file
+    """
+    get_passphrase()
+    lowlevel = cumulus.LowlevelDataStore(options.store)
+    store = cumulus.ObjectStore(lowlevel)
+    for s in snapshots:
+        d = cumulus.parse_full(store.load_snapshot(s))
+        check_version(d['Format'])
+        print d
+        print d['Segments'].split()
+    store.cleanup()
+
+def cmd_read_metadata(args):
+    """ Produce a flattened metadata dump from a snapshot
+    """
+    snapshot = args [0]
+    get_passphrase()
+    lowlevel = cumulus.LowlevelDataStore(options.store)
+    store = cumulus.ObjectStore(lowlevel)
+    d = cumulus.parse_full(store.load_snapshot(snapshot))
+    check_version(d['Format'])
+    metadata = cumulus.read_metadata(store, d['Root'])
+    blank = True
+    for l in metadata:
+        if l == '\n':
+            if blank: continue
+            blank = True
+        else:
+            blank = False
+        sys.stdout.write(l)
+    store.cleanup()
+
+def cmd_verify_snapshots(snapshots):
+    """ Verify snapshot integrity
+    """
+    get_passphrase()
+    lowlevel = cumulus.LowlevelDataStore(options.store)
+    store = cumulus.ObjectStore(lowlevel)
+    for s in snapshots:
+        cumulus.accessed_segments.clear()
+        print "#### Snapshot", s
+        d = cumulus.parse_full(store.load_snapshot(s))
+        check_version(d['Format'])
+        print "## Root:", d['Root']
+        metadata = cumulus.iterate_metadata(store, d['Root'])
+        for m in metadata:
+            if m.fields['type'] not in ('-', 'f'): continue
+            print "%s [%d bytes]" % (m.fields['name'], int(m.fields['size']))
+            verifier = cumulus.ChecksumVerifier(m.fields['checksum'])
+            size = 0
+            for block in m.data():
+                data = store.get(block)
+                verifier.update(data)
+                size += len(data)
+            if int(m.fields['size']) != size:
+                raise ValueError("File size does not match!")
+            if not verifier.valid():
+                raise ValueError("Bad checksum found")
+
+        # Verify that the list of segments included with the snapshot was
+        # actually accurate: covered all segments that were really read, and
+        # doesn't contain duplicates.
+        listed_segments = set(d['Segments'].split())
+        if cumulus.accessed_segments - listed_segments:
+            print "Error: Some segments not listed in descriptor!"
+            print sorted(list(cumulus.accessed_segments - listed_segments))
+        if listed_segments - cumulus.accessed_segments :
+            print "Warning: Extra unused segments listed in descriptor!"
+            print sorted(list(listed_segments - cumulus.accessed_segments))
+    store.cleanup()
+
+def cmd_restore_snapshot(args):
+    """ Restore a snapshot, or some subset of files from it
+    """
+    get_passphrase()
+    lowlevel = cumulus.LowlevelDataStore(options.store)
+    store = cumulus.ObjectStore(lowlevel)
+    snapshot = cumulus.parse_full(store.load_snapshot(args[0]))
+    check_version(snapshot['Format'])
+    destdir = args[1]
+    paths = args[2:]
+
+    def matchpath(path):
+        "Return true if the specified path should be included in the restore."
+
+        # No specification of what to restore => restore everything
+        if len(paths) == 0: return True
+
+        for p in paths:
+            if path == p: return True
+            if path.startswith(p + "/"): return True
+        return False
+
+    def warn(m, msg):
+        print "Warning: %s: %s" % (m.items.name, msg)
+
+    # Phase 1: Read the complete metadata log and create directory structure.
+    metadata_items = []
+    metadata_paths = {}
+    metadata_segments = {}
+    for m in cumulus.iterate_metadata(store, snapshot['Root']):
+        pathname = os.path.normpath(m.items.name)
+        while os.path.isabs(pathname):
+            pathname = pathname[1:]
+        if not matchpath(pathname): continue
+
+        destpath = os.path.join(destdir, pathname)
+        if m.items.type == 'd':
+            path = destpath
+        else:
+            (path, filename) = os.path.split(destpath)
+
+        metadata_items.append((pathname, m))
+        if m.items.type in ('-', 'f'):
+            metadata_paths[pathname] = m
+            for block in m.data():
+                (segment, object, checksum, slice) \
+                    = cumulus.ObjectStore.parse_ref(block)
+                if segment not in metadata_segments:
+                    metadata_segments[segment] = set()
+                metadata_segments[segment].add(pathname)
+
+        try:
+            if not os.path.isdir(path):
+                print "mkdir:", path
+                os.makedirs(path)
+        except Exception, e:
+            warn(m, "Error creating directory structure: %s" % (e,))
+            continue
+
+    # Phase 2: Restore files, ordered by how data is stored in segments.
+    def restore_file(pathname, m):
+        assert m.items.type in ('-', 'f')
+        print "extract:", pathname
+        destpath = os.path.join(destdir, pathname)
+
+        file = open(destpath, 'wb')
+        verifier = cumulus.ChecksumVerifier(m.items.checksum)
+        size = 0
+        for block in m.data():
+            data = store.get(block)
+            verifier.update(data)
+            size += len(data)
+            file.write(data)
+        file.close()
+        if int(m.fields['size']) != size:
+            raise ValueError("File size does not match!")
+        if not verifier.valid():
+            raise ValueError("Bad checksum found")
+
+    while metadata_segments:
+        (segment, items) = metadata_segments.popitem()
+        print "+ Segment", segment
+        for pathname in sorted(items):
+            if pathname in metadata_paths:
+                restore_file(pathname, metadata_paths[pathname])
+                del metadata_paths[pathname]
+
+    print "+ Remaining files"
+    while metadata_paths:
+        (pathname, m) = metadata_paths.popitem()
+        restore_file(pathname, m)
+
+    # Phase 3: Restore special files (symlinks, devices).
+    # Phase 4: Restore directory permissions and modification times.
+    for (pathname, m) in reversed(metadata_items):
+        print "permissions:", pathname
+        destpath = os.path.join(destdir, pathname)
+        (path, filename) = os.path.split(destpath)
+
+        # TODO: Check for ../../../paths that might attempt to write outside
+        # the destination directory.  Maybe also check attempts to follow
+        # symlinks pointing outside?
+
+        try:
+            if m.items.type in ('-', 'f', 'd'):
+                pass
+            elif m.items.type == 'l':
+                try:
+                    target = m.items.target
+                except:
+                    # Old (v0.2 format) name for 'target'
+                    target = m.items.contents
+                os.symlink(target, destpath)
+            elif m.items.type == 'p':
+                os.mkfifo(destpath)
+            elif m.items.type in ('c', 'b'):
+                if m.items.type == 'c':
+                    mode = 0600 | stat.S_IFCHR
+                else:
+                    mode = 0600 | stat.S_IFBLK
+                os.mknod(destpath, mode, os.makedev(*m.items.device))
+            elif m.items.type == 's':
+                pass        # TODO: Implement
+            else:
+                warn(m, "Unknown type code: " + m.items.type)
+                continue
+
+        except Exception, e:
+            warn(m, "Error restoring: %s" % (e,))
+            continue
+
+        try:
+            uid = m.items.user[0]
+            gid = m.items.group[0]
+            os.lchown(destpath, uid, gid)
+        except Exception, e:
+            warn(m, "Error restoring file ownership: %s" % (e,))
+
+        if m.items.type == 'l':
+            continue
+
+        try:
+            os.chmod(destpath, m.items.mode)
+        except Exception, e:
+            warn(m, "Error restoring file permissions: %s" % (e,))
+
+        try:
+            os.utime(destpath, (time.time(), m.items.mtime))
+        except Exception, e:
+            warn(m, "Error restoring file timestamps: %s" % (e,))
+
+    store.cleanup()
+
+def main(argv):
+    usage = ["%prog [option]... command [arg]...", "", "Commands:"]
+    cmd = method = None
+    for cmd, method in globals().iteritems():
+        if cmd.startswith ('cmd_'):
+            usage.append(cmd[4:].replace('_', '-') + ':' + method.__doc__)
+    parser = OptionParser(usage="\n".join(usage))
+    parser.add_option("-v", action="store_true", dest="verbose", default=False,
+                      help="increase verbosity")
+    parser.add_option("-n", action="store_true", dest="dry_run", default=False,
+                      help="dry run")
+    parser.add_option("--store", dest="store",
+                      help="specify path to backup data store")
+    parser.add_option("--localdb", dest="localdb",
+                      help="specify path to local database")
+    parser.add_option("--intent", dest="intent", default=1.0,
+                      help="give expected next snapshot type when cleaning")
+    global options
+    (options, args) = parser.parse_args(argv[1:])
+
+    if len(args) == 0:
+        parser.print_usage()
+        sys.exit(1)
+    cmd = args[0]
+    args = args[1:]
+    method = globals().get('cmd_' + cmd.replace('-', '_'))
+    if method:
+        method (args)
+    else:
+        print "Unknown command:", cmd
+        parser.print_usage()
+        sys.exit(1)