I've tried to setup my brand new Samba 3 server on an x86 Linux machine but it
turns out that "%o" (for old password) doesn't work anymore for "passwd chat"
(while it did work for Solaris with Samba 2.2). I used "passwd chat debug" and
expect just shows an empty password when the old password is filled in (instead
of the one specified to smbpasswd). I've used these settings for smb.conf:

  passwd chat = *old*password* %o\n *new*password* %n\n *new*password* %n\n
*The*NIS*password*has*been*changed*
  passwd chat debug = yes

smbd.log shows:

  expect: expected [*old*password*] received [Changing NIS account information
for proto on einstein.
  Please enter old password:] match yes
[2005/04/28 11:41:14, 10] smbd/chgpasswd.c:expect(286)
  expect: returning True
[2005/04/28 11:41:14, 100] smbd/chgpasswd.c:expect(238)
  expect: sending [
  ]
[2005/04/28 11:41:14, 10] lib/util_sock.c:read_socket_with_timeout(305)
  read_socket_with_timeout: timeout read. select timed out.
[2005/04/28 11:41:14, 100] smbd/chgpasswd.c:expect(275)
  expect: expected [*new*password*] received [
  Changing NIS password for proto on einstein.
  Please enter new password:] match yes