docker login
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选项::

    Usage:  docker login [OPTIONS] [SERVER]
    Log in to a Docker registry
    Options:
      -p, --password string   Password
          --password-stdin    Take the password from stdin
      -u, --username string   Username

实例::

    $ docker login --username=luxl2@14177974xx804x7 registry.cn-beijing.aliyuncs.com