[Nbd] my problem with exporting raw partition from server

[Lin Qiao <lqiao@...5...>]

Hi,

I'm a newbie in using NBD.  I used NBD 2.6 and redhat linux 8.0. I want to 
export /dev/sda4 (2G) from server1.

>nbd-server 30056 /dev/sda4
  
However, when I tried to connect from the client, I 
got the following message,
>nbd-client server1 30056 /dev/nbd0
Negotiation: Server closed connection.

I can correctly set up the connection if I export a file from server1.
>From server1
>dd if=/dev/zero of=/temp bs=1048576 count=100
>nbd-server 30055 /temp
>From client
>nbd-client server1 30055 /dev/nbd1
Negotiate: ..size=102400KB
bs=1024, sz=102400

Please help me resovle this problem or show me any hint!

Thanks a lot!

Lin