There is none "inet addr:" or "mask:".
 

My linux system is build one file by one from another system RH9.And I come to the step:install networking. When I had run "insmod mii,insmod 3c905,ifconfig eth0 up",the command "ifconfig" echo the message without "inet addr:X.X.X.X mask:X.X.X.X".

I have checked the ifcfg-eth0. It's right.

I consider that there are someting I haven't copy enough file and miss some operations.

Can somebody help me???

And my system has not loopback either, I don't know how to add the loopback device

Make sure you copied all the init-scripts from /etc/rc.d/* directory. Especially you would be interested in the scripts related to network and internet.

If everything is installed properly your network will start when you boot but you can manually start it like this:
/etc/rc.d/init.d/network start