Vnx-rootfsdragon

How to use DRAGON GMPLS UML root filesystem with VNX

The DRAGON (Dynamic Resource Allocation via GMPLS Optical Networks) project is conducting research and developing technologies to enable dynamic provisioning of network resources on an interdoman basis across heterogeneous network technologies. As part of the project they provide instructions for simulating a GMPLS network using User Mode Linux root filesystem.

This documents is a quick recipe describing how to use DRAGON's UML root filesystem with VNX.

VNX supports User-Mode-Linux virtual machines, so the root filesystem and kernels provided by DRAGON's project can be directly used after making the standard modifications to the rootfs.

However, neither the kernel nor the root filesystem include support for iso9660 filesystem format, which is needed by VNX to autoconfigure virtual machines once started.

So, to use DRAGON's rootfs we need to rebuild the UML kernel with iso9600 support. The procedure described below has been tested over an Ubuntu 10.04.4 32 bits system. It does NOT work as it is over a 64 bits system, even using the SUBARCH=i386 compilation option.

Recompiling kernel:

NOTE: if you do not want to follow the procedure you can download the modified kernel from here.

• Download DRAGON kernel config file:

wget http://dragon.maxgigapop.net/twiki/pub/DRAGON/UserModeLinux/uml_linux-2.6.27.8.config

• Install VDE2 if not already installed:

apt-get install vde2 libvdeplug2-dev

• Download kernel 2.6.27.8 sources and uncompress them:

wget http://www.kernel.org/pub/linux/kernel/v2.6/linux-2.6.27.8.tar.gz
tar xfvz linux-2.6.27.8.tar.gz 
cd linux-2.6.27.8

• Edit arch/um/drivers/vde_user.c and change 'kmalloc' por 'uml_kmalloc' to avoid a compilation error
• Download mconsole kernel patch and apply it:

wget http://wiki.strongswan.org/projects/strongswan/repository/revisions/693a244d0fddccd11f3a18112519d3593e0eb197/raw/src/dumm/patches/mconsole-exec-2.6.27.patch
patch -p1 < mconsole-exec-2.6.27.patch

• Download another kernel patch to avoid the "buffer overflow detected" panic error (taken from here) and apply it:

wget http://idefix.dit.upm.es/vnx/filesystems/dragon-gmpls/kernel-buffer-overflow.patch
patch -p1 < kernel-buffer-overflow.patch

• Configure and compile kernel and modules using gcc-4.4 or older

make defconfig ARCH=um CC=gcc-4.4
cp ../uml_linux-2.6.27.8.config .config
sed -i -e 's/CONFIG_ISO9660_FS=m/CONFIG_ISO9660_FS=y/' .config
make ARCH=um CC=gcc-4.4

• Strip the kernel and copy it to VNX kernel directory:

strip linux 
cp linux /usr/share/vnx/kernels/uml_linux-2.6.27.8-vnx
chmod +x /usr/share/vnx/kernels/uml_linux-2.6.27.8-vnx

Modifiyng root filesystem:

• Download dragon rootfs and uncompress it:

wget http://dragon.maxgigapop.net/twiki/pub/DRAGON/UserModeLinux/Debian-4.0-x86-root_fs-2008Dec10.bz2
bunzip2 Debian-4.0-x86-root_fs-2008Dec10.bz2

• Prepare rootfs to be used with VNX:

mkdir /mnt/dragon
mount -o loop Debian-4.0-x86-root_fs-2008Dec10 /mnt/dragon
chroot /mnt/dragon
echo '/dev/ubdb    /mnt/vnuml     iso9660  defaults   0 0' >> /etc/fstab
mkdir /mnt/vnuml
mkdir /mnt/hostfs
ln -s /mnt/vnuml/umlboot /etc/rc2.d/S11umlboot
exit
pushd /mnt/dragon/dev
wget http://www.theshore.net/~caker/uml/makeUBDdev.sh
chmod a+x makeUBDdev.sh
./makeUBDdev.sh
rm makeUBDdev.sh

• Exit rootfs directories and unmount it:

popd
umount /mnt/dragon

• Copy the root filesystem to VNX directory:

cp Debian-4.0-x86-root_fs-2008Dec10 /usr/share/vnx/filesystems/Debian-4.0-x86-root_fs-2008Dec10-vnx

Installing new software:

• Mount the rootfs and chroot to it:

mount -o loop /usr/share/vnx/filesystems/Debian-4.0-x86-root_fs-2008Dec10-vnx /mnt/dragon
chroot /mnt/dragon

• Edit /etc/resolv.conf and configure the DNS ip address
• Test that you have network connectivity and make the desired changes
• Once finished, exit chroot and unmount

exit
umount /mnt/dragon

Testing:

• Install VNX (see instructions here)
• Create a file named dragon.xml with the following content:

<?xml version="1.0" encoding="UTF-8"?>
<!--
~~~~~~~~~~~~~~~~~~~~
VNX Sample scenarios
~~~~~~~~~~~~~~~~~~~~
Name:        dragon
Description: Simple example to show two virtual machines running DRAGON's rootfs connected
             to a network.
             The host has an interface in Net0 with address 10.0.0.1  

This file is part of the Virtual Networks over LinuX (VNX) Project distribution. 
(www: http://www.dit.upm.es/vnx - e-mail: vnx@dit.upm.es) 

Departamento de Ingenieria de Sistemas Telematicos (DIT)
Universidad Politecnica de Madrid
SPAIN
-->

<vnx xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
  xsi:noNamespaceSchemaLocation="/usr/share/xml/vnx/vnx-2.00.xsd">
  <global>
    <version>2.0</version>
    <scenario_name>simple_uml-dragon</scenario_name>
    <automac offset="2"/>
    <!--vm_mgmt type="none" /-->
    <vm_mgmt type="private" network="10.250.0.0" mask="24" offset="8">
       <host_mapping />
    </vm_mgmt> 
    <vm_defaults>
        <exec_mode type="uml">net</exec_mode>
    </vm_defaults>
  </global>

  <net name="Net0" mode="virtual_bridge" />

  <vm name="vm1" type="uml" subtype="" os="">
    <filesystem type="cow">/usr/share/vnx/filesystems/Debian-4.0-x86-root_fs-2008Dec10-vnx</filesystem>
    <mem>256M</mem>
    <kernel trace="on">/usr/share/vnx/kernels/uml_linux-2.6.27.8-vnx</kernel>
    <console id="0" display="yes">xterm</console>
    <if id="1" net="Net0">
      <ipv4>10.0.0.20/24</ipv4>
    </if>
  </vm>

  <vm name="vm2" type="uml" subtype="" os="">
    <filesystem type="cow">/usr/share/vnx/filesystems/Debian-4.0-x86-root_fs-2008Dec10-vnx</filesystem>
    <mem>256M</mem>
    <kernel trace="on">/usr/share/vnx/kernels/uml_linux-2.6.27.8-vnx</kernel>
    <console id="0" display="yes">xterm</console>
    <if id="1" net="Net0">
      <ipv4>10.0.0.21/24</ipv4>
    </if>
  </vm>

  <host>
    <hostif net="Net0">
       <ipv4>10.0.0.1/24</ipv4>
    </hostif>
  </host>
  
</vnx>

• Start the scenario with:

vnx -f dragon.xml -v -t