[Samba] error

[sandy.napoles at eccmg.cupet.cu]

and, when I run this other commands

./samba-tool domain join eccmg.cupet.cu DC -Usandy --realm=eccmg.cupet.cu
Finding a writeable DC for domain 'eccmg.cupet.cu'
ERROR(exception): uncaught exception - Failed to find a writeable DC for
domain 'eccmg.cupet.cu'
  File
"/usr/local/samba/lib/python2.6/site-packages/samba/netcmd/__init__.py",
line 160, in _run
    return self.run(*args, **kwargs)
  File
"/usr/local/samba/lib/python2.6/site-packages/samba/netcmd/domain.py",
line 184, in run
    machinepass=machinepass, use_ntvfs=use_ntvfs)
  File "/usr/local/samba/lib/python2.6/site-packages/samba/join.py", line
943, in join_DC
    machinepass, use_ntvfs)
  File "/usr/local/samba/lib/python2.6/site-packages/samba/join.py", line
65, in __init__
    ctx.server = ctx.find_dc(domain)
  File "/usr/local/samba/lib/python2.6/site-packages/samba/join.py", line
203, in find_dc
    raise Exception("Failed to find a writeable DC for domain '%s'" % domain)
root at orion:/usr/local/samba/bin#