If I have a few old computers, no monitors, no display cards,
I want to connect them to network， install Linux system and run Blender in console only,
so they can just work for network rendering...

Is it possible? And how to do it?
Thanks.

http://wiki.blender.org/index.php/Doc:2.6/Manual/Render/Performance/Netrender

There is the section "Command Line" which specifies the procedure of starting slaves from command line. (You need to configure and save the configurations first on some another system if I understood this correctly - I am running X on couple of Linux machines and configure the slaves straight through the GUI).

So this is somewhat how the procedure goes:

1. Configure a slave on a blender system you have a GUI in. Save this configuration as 'slave.blend'.
2. Copy this to your Linux system you wish to be your slave

From command line:
scp slave.blend <username>@<target-ip>:~/<target-directory>

3. Start blender on that system from command line

Connect to the remote system:
ssh <username>@<target-ip>
Start Blender with the slave configuration
blender -b slave.blend -a

I don't know how familiar you are with Linux so sorry if these things are self-evident. Anyway I managed to start the slave with the procedure described above only using ssh from another machine.

Thank you very much, ptraejar!
This wiki is very useful.