diff -rN -u old-unicode/src/allmydata/scripts/tahoe_backup.py new-unicode/src/allmydata/scripts/tahoe_backup.py
--- old-unicode/src/allmydata/scripts/tahoe_backup.py	2009-04-08 22:55:52.000000000 -0600
+++ new-unicode/src/allmydata/scripts/tahoe_backup.py	2009-04-08 22:55:55.000000000 -0600
@@ -4,11 +4,15 @@
 import urllib
 import simplejson
 import datetime
+import sys
 from allmydata.scripts.common import get_alias, escape_path, DEFAULT_ALIAS
 from allmydata.scripts.common_http import do_http
 from allmydata import uri
 from allmydata.util import time_format
 from allmydata.scripts import backupdb
+from allmydata.util.stringutils import fs_to_unicode, unicode_to_fs
+from allmydata.util.assertutil import precondition
+from twisted.python import usage
 
 class HTTPError(Exception):
     pass
@@ -248,6 +252,7 @@
             print >>self.options.stdout, msg
 
     def process(self, localpath, olddircap):
+        precondition(isinstance(localpath, unicode), localpath)
         # returns newdircap
 
         self.verboseprint("processing %s, olddircap %s" % (localpath, olddircap))
@@ -256,7 +261,8 @@
             olddircontents = self.readdir(olddircap)
 
         newdircontents = {} # childname -> (type, rocap, metadata)
-        for child in self.options.filter_listdir(os.listdir(localpath)):
+        for child in self.options.filter_listdir(os.listdir(unicode_to_fs(localpath))):
+            child = fs_to_unicode(child)
             childpath = os.path.join(localpath, child)
             if os.path.isdir(childpath):
                 metadata = get_local_metadata(childpath)
@@ -342,6 +348,8 @@
         return contents
 
     def upload(self, childpath):
+        precondition(isinstance(childpath, unicode), childpath)
+
         #self.verboseprint("uploading %s.." % childpath)
         metadata = get_local_metadata(childpath)
 
@@ -350,7 +358,7 @@
 
         if must_upload:
             self.verboseprint("uploading %s.." % childpath)
-            infileobj = open(os.path.expanduser(childpath), "rb")
+            infileobj = open(unicode_to_fs(os.path.expanduser(childpath)), "rb")
             url = self.options['node-url'] + "uri"
             resp = do_http("PUT", url, infileobj)
             if resp.status not in (200, 201):
diff -rN -u old-unicode/src/allmydata/scripts/tahoe_cp.py new-unicode/src/allmydata/scripts/tahoe_cp.py
--- old-unicode/src/allmydata/scripts/tahoe_cp.py	2009-04-08 22:55:53.000000000 -0600
+++ new-unicode/src/allmydata/scripts/tahoe_cp.py	2009-04-08 22:55:55.000000000 -0600
@@ -4,9 +4,13 @@
 import simplejson
 from cStringIO import StringIO
 from twisted.python.failure import Failure
+import sys
 from allmydata.scripts.common import get_alias, escape_path, DefaultAliasMarker
 from allmydata.scripts.common_http import do_http
 from allmydata import uri
+from twisted.python import usage
+from allmydata.util.stringutils import fs_to_unicode, unicode_to_fs
+from allmydata.util.assertutil import precondition
 
 def ascii_or_none(s):
     if s is None:
@@ -69,6 +73,7 @@
 
 class LocalFileSource:
     def __init__(self, pathname):
+        precondition(isinstance(pathname, unicode), pathname)
         self.pathname = pathname
 
     def need_to_copy_bytes(self):
@@ -79,6 +84,7 @@
 
 class LocalFileTarget:
     def __init__(self, pathname):
+        precondition(isinstance(pathname, unicode), pathname)
         self.pathname = pathname
     def put_file(self, inf):
         outf = open(self.pathname, "wb")
@@ -91,6 +97,7 @@
 
 class LocalMissingTarget:
     def __init__(self, pathname):
+        precondition(isinstance(pathname, unicode), pathname)
         self.pathname = pathname
 
     def put_file(self, inf):
@@ -104,6 +111,8 @@
 
 class LocalDirectorySource:
     def __init__(self, progressfunc, pathname):
+        precondition(isinstance(pathname, unicode), pathname)
+
         self.progressfunc = progressfunc
         self.pathname = pathname
         self.children = None
@@ -112,8 +121,9 @@
         if self.children is not None:
             return
         self.children = {}
-        children = os.listdir(self.pathname)
+        children = os.listdir(unicode_to_fs(self.pathname))
         for i,n in enumerate(children):
+            n = fs_to_unicode(n)
             self.progressfunc("examining %d of %d" % (i, len(children)))
             pn = os.path.join(self.pathname, n)
             if os.path.isdir(pn):
@@ -129,6 +139,8 @@
 
 class LocalDirectoryTarget:
     def __init__(self, progressfunc, pathname):
+        precondition(isinstance(pathname, unicode), pathname)
+
         self.progressfunc = progressfunc
         self.pathname = pathname
         self.children = None
@@ -137,8 +149,9 @@
         if self.children is not None:
             return
         self.children = {}
-        children = os.listdir(self.pathname)
+        children = os.listdir(unicode_to_fs(self.pathname))
         for i,n in enumerate(children):
+            n = fs_to_unicode(n)
             self.progressfunc("examining %d of %d" % (i, len(children)))
             pn = os.path.join(self.pathname, n)
             if os.path.isdir(pn):
@@ -160,8 +173,9 @@
         return LocalDirectoryTarget(self.progressfunc, pathname)
 
     def put_file(self, name, inf):
+        precondition(isinstance(name, unicode), name)
         pathname = os.path.join(self.pathname, name)
-        outf = open(pathname, "wb")
+        outf = open(unicode_to_fs(pathname), "wb")
         while True:
             data = inf.read(32768)
             if not data:
diff -rN -u old-unicode/src/allmydata/scripts/tahoe_ls.py new-unicode/src/allmydata/scripts/tahoe_ls.py
--- old-unicode/src/allmydata/scripts/tahoe_ls.py	2009-04-08 22:55:53.000000000 -0600
+++ new-unicode/src/allmydata/scripts/tahoe_ls.py	2009-04-08 22:55:55.000000000 -0600
@@ -86,9 +86,9 @@
         elif childtype == "filenode":
             t0 = "-"
             size = str(child[1]['size'])
-            classify = ""
+            classify = u""
             if rw_uri:
-                classify = "*"
+                classify = u"*"
         else:
             t0 = "?"
             size = "?"
diff -rN -u old-unicode/src/allmydata/test/test_cli.py new-unicode/src/allmydata/test/test_cli.py
--- old-unicode/src/allmydata/test/test_cli.py	2009-04-08 22:55:53.000000000 -0600
+++ new-unicode/src/allmydata/test/test_cli.py	2009-04-08 22:55:56.000000000 -0600
@@ -1,5 +1,6 @@
 # coding=utf-8
 
+import sys
 import os.path
 from twisted.trial import unittest
 from cStringIO import StringIO
@@ -518,6 +519,41 @@
             self._test_webopen(["two:"], self.two_url)
         d.addCallback(_test_urls)
 
+        d.addCallback(lambda res: self.do_cli("create-alias", "études"))
+        def _check_create_unicode((rc,stdout,stderr)):
+            self.failUnlessEqual(rc, 0)
+            self.failIf(stderr)
+
+            # If stdout only supports ascii, accentuated characters are
+            # being replaced by '?'
+            if sys.stdout.encoding == "ANSI_X3.4-1968":
+                self.failUnless("Alias '?tudes' created" in stdout)
+            else:
+                self.failUnless("Alias 'études' created" in stdout)
+
+            aliases = get_aliases(self.get_clientdir())
+            self.failUnless(aliases[u"études"].startswith("URI:DIR2:"))
+        d.addCallback(_check_create_unicode)
+
+        d.addCallback(lambda res: self.do_cli("ls", "études:"))
+        def _check_ls1((rc, stdout, stderr)):
+            self.failUnlessEqual(rc, 0)
+            self.failIf(stderr)
+
+            self.failUnlessEqual(stdout, "")
+        d.addCallback(_check_ls1)
+
+        d.addCallback(lambda res: self.do_cli("put", "-", "études:uploaded.txt",
+          stdin="Blah blah blah"))
+
+        d.addCallback(lambda res: self.do_cli("ls", "études:"))
+        def _check_ls2((rc, stdout, stderr)):
+            self.failUnlessEqual(rc, 0)
+            self.failIf(stderr)
+
+            self.failUnlessEqual(stdout, "uploaded.txt\n")
+        d.addCallback(_check_ls2)
+
         return d
 
 class Put(GridTestMixin, CLITestMixin, unittest.TestCase):
@@ -739,6 +775,37 @@
         d.addCallback(lambda (rc,out,err): self.failUnlessEqual(out, DATA2))
         return d
 
+    def test_immutable_from_file_unicode(self):
+        # tahoe put file.txt "à trier.txt"
+        self.basedir = os.path.dirname(self.mktemp())
+        self.set_up_grid()
+
+        rel_fn = os.path.join(self.basedir, "DATAFILE")
+        abs_fn = os.path.abspath(rel_fn)
+        # we make the file small enough to fit in a LIT file, for speed
+        DATA = "short file"
+        f = open(rel_fn, "w")
+        f.write(DATA)
+        f.close()
+
+        d = self.do_cli("create-alias", "tahoe")
+
+        d.addCallback(lambda res:
+                      self.do_cli("put", rel_fn, "à trier.txt"))
+        def _uploaded((rc,stdout,stderr)):
+            readcap = stdout.strip()
+            self.failUnless(readcap.startswith("URI:LIT:"))
+            self.failUnless("201 Created" in stderr, stderr)
+            self.readcap = readcap
+        d.addCallback(_uploaded)
+
+        d.addCallback(lambda res:
+                      self.do_cli("get", "tahoe:à trier.txt"))
+        d.addCallback(lambda (rc,stdout,stderr):
+                      self.failUnlessEqual(stdout, DATA))
+
+        return d
+
 class List(GridTestMixin, CLITestMixin, unittest.TestCase):
     def test_list(self):
         self.basedir = "cli/List/list"
@@ -795,30 +862,37 @@
     def test_unicode_filename(self):
         self.basedir = "cli/Cp/unicode_filename"
         self.set_up_grid()
+        d = self.do_cli("create-alias", "tahoe")
+
+        # Use unicode strings when calling os functions
+        if sys.getfilesystemencoding() == "ANSI_X3.4-1968":
+            fn1 = os.path.join(self.basedir, u"Artonwall")
+        else:
+            fn1 = os.path.join(self.basedir, u"Ärtonwall")
 
-        fn1 = os.path.join(self.basedir, "Ärtonwall")
         DATA1 = "unicode file content"
         open(fn1, "wb").write(DATA1)
+        d.addCallback(lambda res: self.do_cli("cp", fn1.encode('utf-8'), "tahoe:Ärtonwall"))
+
+        d.addCallback(lambda res: self.do_cli("get", "tahoe:Ärtonwall"))
+        d.addCallback(lambda (rc,out,err): self.failUnlessEqual(out, DATA1))
 
-        fn2 = os.path.join(self.basedir, "Metallica")
+
+        fn2 = os.path.join(self.basedir, u"Metallica")
         DATA2 = "non-unicode file content"
         open(fn2, "wb").write(DATA2)
 
         # Bug #534
         # Assure that uploading a file whose name contains unicode character doesn't
         # prevent further uploads in the same directory
-        d = self.do_cli("create-alias", "tahoe")
-        d.addCallback(lambda res: self.do_cli("cp", fn1, "tahoe:"))
-        d.addCallback(lambda res: self.do_cli("cp", fn2, "tahoe:"))
-
-        d.addCallback(lambda res: self.do_cli("get", "tahoe:Ärtonwall"))
-        d.addCallback(lambda (rc,out,err): self.failUnlessEqual(out, DATA1))
+        d.addCallback(lambda res: self.do_cli("cp", fn2.encode('utf-8'), "tahoe:"))
 
         d.addCallback(lambda res: self.do_cli("get", "tahoe:Metallica"))
         d.addCallback(lambda (rc,out,err): self.failUnlessEqual(out, DATA2))
 
+        d.addCallback(lambda res: self.do_cli("ls", "tahoe:"))
+
         return d
-    test_unicode_filename.todo = "This behavior is not yet supported, although it does happen to work (for reasons that are ill-understood) on many platforms.  See issue ticket #534."
 
     def test_dangling_symlink_vs_recursion(self):
         if not hasattr(os, 'symlink'):
@@ -837,6 +911,17 @@
                                               dn, "tahoe:"))
         return d
 
+class Mkdir(GridTestMixin, CLITestMixin, unittest.TestCase):
+    def test_unicode_mkdir(self):
+        self.basedir = os.path.dirname(self.mktemp())
+        self.set_up_grid()
+
+        d = self.do_cli("create-alias", "tahoe")
+        d.addCallback(lambda res: self.do_cli("mkdir", "tahoe:Motörhead"))
+
+        return d
+
+
 class Backup(GridTestMixin, CLITestMixin, StallMixin, unittest.TestCase):
 
     def writeto(self, path, data):
@@ -871,6 +956,11 @@
         self.writeto("parent/subdir/bar.txt", "bar\n" * 1000)
         self.writeto("parent/blah.txt", "blah")
 
+        if sys.getfilesystemencoding() == "ANSI_X3.4-1968":
+            self.writeto(u"parent/artonwall.txt", "Marmelade Jacuzzi")
+        else:
+            self.writeto(u"parent/ärtonwall.txt", "Marmelade Jacuzzi")
+
         def do_backup(use_backupdb=True, verbose=False):
             cmd = ["backup"]
             if not have_bdb or not use_backupdb:
@@ -895,8 +985,8 @@
             self.failUnlessEqual(err, "")
             self.failUnlessEqual(rc, 0)
             fu, fr, dc, dr = self.count_output(out)
-            # foo.txt, bar.txt, blah.txt
-            self.failUnlessEqual(fu, 3)
+            # foo.txt, bar.txt, blah.txt, ärtonwall.txt
+            self.failUnlessEqual(fu, 4)
             self.failUnlessEqual(fr, 0)
             # empty, home, home/parent, home/parent/subdir
             self.failUnlessEqual(dc, 4)
@@ -945,9 +1035,9 @@
             self.failUnlessEqual(rc, 0)
             if have_bdb:
                 fu, fr, dc, dr = self.count_output(out)
-                # foo.txt, bar.txt, blah.txt
+                # foo.txt, bar.txt, blah.txt, ärtonwall.txt
                 self.failUnlessEqual(fu, 0)
-                self.failUnlessEqual(fr, 3)
+                self.failUnlessEqual(fr, 4)
                 # empty, home, home/parent, home/parent/subdir
                 self.failUnlessEqual(dc, 0)
                 self.failUnlessEqual(dr, 4)
@@ -975,9 +1065,9 @@
                 self.failUnlessEqual(rc, 0)
                 fu, fr, dc, dr = self.count_output(out)
                 fchecked, dchecked, dread = self.count_output2(out)
-                self.failUnlessEqual(fchecked, 3)
+                self.failUnlessEqual(fchecked, 4)
                 self.failUnlessEqual(fu, 0)
-                self.failUnlessEqual(fr, 3)
+                self.failUnlessEqual(fr, 4)
                 # TODO: backupdb doesn't do dirs yet; when it does, this will
                 # change to dchecked=4, and maybe dread=0
                 self.failUnlessEqual(dchecked, 0)
@@ -1023,8 +1113,8 @@
                 fu, fr, dc, dr = self.count_output(out)
                 # new foo.txt, surprise file, subfile, empty
                 self.failUnlessEqual(fu, 4)
-                # old bar.txt
-                self.failUnlessEqual(fr, 1)
+                # old bar.txt, ärtonwall.txt
+                self.failUnlessEqual(fr, 2)
                 # home, parent, subdir, blah.txt, surprisedir
                 self.failUnlessEqual(dc, 5)
                 self.failUnlessEqual(dr, 0)
@@ -1063,7 +1153,7 @@
             self.failUnlessEqual(err, "")
             self.failUnlessEqual(rc, 0)
             fu, fr, dc, dr = self.count_output(out)
-            self.failUnlessEqual(fu, 5)
+            self.failUnlessEqual(fu, 6)
             self.failUnlessEqual(fr, 0)
             self.failUnlessEqual(dc, 0)
             self.failUnlessEqual(dr, 5)
diff -rN -u old-unicode/src/allmydata/util/stringutils.py new-unicode/src/allmydata/util/stringutils.py
--- old-unicode/src/allmydata/util/stringutils.py	1969-12-31 17:00:00.000000000 -0700
+++ new-unicode/src/allmydata/util/stringutils.py	2009-04-08 22:55:56.000000000 -0600
@@ -0,0 +1,39 @@
+"""
+Functions used to convert inputs from whatever encoding used in the system to
+unicode and back.
+
+TODO:
+  * Accept two cli arguments --argv-encoding and --filesystem-encoding
+"""
+
+import sys
+from allmydata.util.assertutil import precondition
+from twisted.python import usage
+
+def fs_to_unicode(s):
+    """
+    Decode a filename (or a directory name) to unicode using the same encoding
+    as the filesystem.
+    """
+    # Filename encoding detection is a little bit better thanks to
+    # getfilesystemencoding() in the sys module. However, filenames can be
+    # encoded using another encoding than the one used on the filesystem.
+
+    precondition(isinstance(s, str), s)
+    encoding = sys.getfilesystemencoding()
+    try:
+        return unicode(s, encoding)
+    except UnicodeDecodeError:
+        raise usage.UsageError("Filename '%s' cannot be decoded using the current encoding of your filesystem (%s). Please rename this file." % (s, encoding))
+
+def unicode_to_fs(s):
+    """
+    Encode an unicode object used in file or directoy name.
+    """
+
+    precondition(isinstance(s, unicode), s)
+    encoding = sys.getfilesystemencoding()
+    try:
+        return s.encode(encoding)
+    except UnicodeEncodeError:
+        raise usage.UsageError("Filename '%s' cannot be encoded using the current encoding of your filesystem (%s). Please configure your locale correctly or rename this file." % (s, encoding))