script to start UML (User Mode Linux).

host

$ ifconfig
eth0      Link encap:Ethernet  HWaddr 00:50:fc:99:96:e3  
          inet addr:10.0.0.1  Bcast:10.255.255.255  Mask:255.0.0.0
          inet6 addr: fe80::250:fcff:fe99:96e3/64 Scope:Link
          UP BROADCAST RUNNING MULTICAST  MTU:1500  Metric:1
          RX packets:36311 errors:0 dropped:0 overruns:0 frame:0
          TX packets:36902 errors:0 dropped:0 overruns:0 carrier:0
          collisions:0 txqueuelen:1000 
          RX bytes:24450223 (24.4 MB)  TX bytes:6426466 (6.4 MB)
          Interrupt:16 Base address:0xe800 

tap0      Link encap:Ethernet  HWaddr da:d3:37:23:d3:35  
          inet addr:10.0.0.1  Bcast:10.255.255.255  Mask:255.0.0.0
          inet6 addr: fe80::d8d3:37ff:fe23:d335/64 Scope:Link
          UP BROADCAST RUNNING MULTICAST  MTU:1500  Metric:1
          RX packets:17 errors:0 dropped:0 overruns:0 frame:0
          TX packets:39 errors:0 dropped:0 overruns:0 carrier:0
          collisions:0 txqueuelen:500 
          RX bytes:4230 (4.2 KB)  TX bytes:6323 (6.3 KB)

uml

$ifconfig eth0 10.0.0.2 up
$ route add default gw 10.0.0.1

# Now UML should be able to connect to outside world

uml_debian_start.sh

#!/bin/bash
# TODO:
# Set var for tuntap dev name instead of hardcoded 'tap0'.
# Set var for IP ADDR for tuntap dev
# Set var for tuntap dev owner
# Set var for host's dev name in which connected to gw internet

# Global vars
KERNEL_BIN=/home/akeda/Learn/user-linux-mode/kernel-3.2.35/kernel32-3.2.35
DEBIAN_FS_FILE=/home/akeda/Learn/user-linux-mode/kernel-3.2.35/Debian-Squeeze-x86-root_fs
ALLOCATED_MEM_SIZE=512M

echo 'Setting up tap0'
sudo tunctl -d tap0
sudo tunctl -u akeda -t tap0
sudo ifconfig tap0 10.0.0.1 up

echo 'Seting up iptables'
sudo iptables --flush
sudo iptables --table nat --flush
sudo iptables --delete-chain
sudo iptables --table nat --delete-chain
sudo iptables --table nat --append POSTROUTING --out-interface eth0 -j MASQUERADE
sudo iptables --append FORWARD --in-interface tap0 -j ACCEPT

echo 'Enabling IP forwarding'
sudo sysctl net.ipv4.ip_forward=1
sudo sysctl net.ipv4.conf.tap0.proxy_arp=1
sudo arp -Ds 10.0.0.2 eth0 pub
sudo route add -host 10.0.0.2 dev tap0

echo 'Running Debian UML'

CMD="$KERNEL_BIN ubda=$DEBIAN_FS_FILE mem=$ALLOCATED_MEM_SIZE eth0=tuntap,tap0,,10.0.0.1 umid=debian"
$CMD