GeekyLog - BlueT's LoGeeks, Logics of Geek Thinks.

Once you install and setup KVM, configure kvm itself and system network bridge interface correctly on your Ubuntu server,
you can now starting to build a guest OS / disk image, run it, and use iptables to forward connections to those new VPSes.

Build guest:

HTTP_PROXY="Proxy_IP:Port" sudo ubuntu-vm-builder kvm hardy \
  --dest 'DEST_DIR'\
  --hostname 'GUEST_HOSTNAME'\
  --ip 'GUEST_IP_YOU_WANT'\
  --arch 'i386'\
  --mem '256'\
  --rootsize '4096'\
  --swapsize '1024'\
  --kernel-flavour 'virtual'\
  --domain 'bluet.org'\
  --mirror 'http://ftp.twaren.net/ubuntu'\
  --components 'main,universe,multiverse,restricted'\
  --addpkg ssh --addpkg vim  --addpkg unattended-upgrades --addpkg acpid\
  --name 'Default_User_Name'  --user 'Default_User_Account'  --pass 'Default_User_Password'\
  --mask '255.255.255.0'\
  --net '192.168.122.0'\
  --bcast '192.168.122.255'\
  --gw '192.168.122.1'\
  --dns '192.168.122.1'\
  --tmp '/dev/shm/'\
  --libvirt qemu:///system ;

Modify that to fit your needs.

Forward "connections to specific port on HostOS" to a specific port on GuestOS (VPS):

Run these commands in HostOS:

$ sudo iptables -t nat -I PREROUTING -p tcp -d HostOS_IP --dport HostOS_Port -j DNAT --to GuestOS_IP:GuestOS_Port
$ sudo iptables -A FORWARD -p tcp -d GuestOS --dport GuestOS_Port -j ACCEPT

For example, if you want to ssh to your VPS, you can pick a spare (not-using by other application) port, and forward "connections to the specified port on HostOS" to the GuestOS's port 22.
Let's say, when HostOS is using IP 192.168.1.2, GuestOS is using IP 192.168.122.2, the choosen port on HostOS is 10022, you can do the following commands.

$ sudo iptables -t nat -I PREROUTING -p tcp -d 192.168.1.2 --dport 10022 -j DNAT --to 192.168.122.2:22
$ sudo iptables -A FORWARD -p tcp -d 192.168.122.2 --dport 22 -j ACCEPT

Finally, you got a configured VPS, you can start running it and ssh into it.

Start the VPS:
If your GuestOS' hostname is "vps01", you can do this to start running it:
$ virsh start vps01
And then ssh into it:
$ ssh -v 192.168.1.2 -p 10022


Refs: KVM document page on ubuntu.com

1. I got 4G ram installed on my IBM X61 Laptop, with Ubuntu 9.04 Jaunty Desktop for i386 installed.
2. I need to use my whole 4G of ram bcoz I always has about 400 tabs opened in my Firefox.

All 32bit system can allocat only 33.5G of memory.

X61 uses Intel chips and VGA chip, which is some kind of shit.
Want to improve the xorg's intel driver, you got to install the latest kernel and driver, with UXA mode enabled.
Then, you might get glxgear score about 700~800fps, nice.

Now here comes the problem.
Kernel's PEM conflicts with UXA, and makes the UXA's advanced GPU memory handling unusable.
So I can only have two choice:
1. Use generic kernel and better graphic performance, but only 3G of ram. But my memory is always full.
2. Use server kernel, got whole 4G of ram, but the glxgear score is only about 220fps. Sucks!

With 64bit system, the kernel can natively support to 64G of ram, so I can use 64bit generic kernel with whole my 4G of ram and enjoy the 800fps glxgear score. That's Great!

BUT, How To Install a AMD64 (64bit) Kernel on my i386 (32bit) System?
I did some google search but still find nothing really helpful...