Installing Xen on Debian Etch is easy.

Just install it with Aptitude or apt-get.

http://seldon.cocolog-nifty.com/petapeta/2007/04/etch_xen.html is extremely helpful.

And right now, I am creating an image 😀

>>>> Added at 23:17

After that, I ran into more trouble than expected. It seems the cause was that I had assigned multiple addresses to eth0.
In the end, I removed eth0:1, ran

network-bridge start vifnum=0

and then ran xm create hoge, which worked.

I ended up researching it for about 3 hours… orz.