Vnx-rootfsdebian

How to create a User-Mode-Linux Debian root-file-system for VNX

Follow this procedure to create a UML Debian Squeeze (6.0) root filesystem for VNX.

Basic installation and configuration

• Requirements:

apt-get install debootstrap

• Create and format the file that will host the filesystem:

dd bs=1M if=/dev/zero of=vnx_rootfs_uml_debian.img count=2048
mkfs.ext4 vnx_rootfs_uml_debian.img 

• Mount it and and use debootstrap to populate it:

mkdir mnt
mount -o loop vnx_rootfs_uml_debian.img mnt/
debootstrap --arch i386 squeeze mnt/ ftp://ftp.debian.org/debian/

Note: change ftp.debian.org to the mirror nearest you (e.g. ftp.es.debian.org).

• Chroot to the new filesystem to continue the installation:

mount -t proc none mnt/proc
chroot mnt
env -update
ln -sf /usr/share/zoneinfo/Europe/Madrid /etc/localtime 

• Install the packages desired. For example, for a root filesystem mainly used in networking laboratories:

apt-get install locales aptsh file less perl-modules vim openssh-server    \
   openssh-client telnet sudo lsof ssh ncurses-term bzip2 strace   \
   tcpdump tshark apache2 apache2-utils dnsutils finger ftp ftpd   \
   ipsec-tools iputils-tracepath ipv6calc ipvsadm lpr lynx         \
   nfs-common openssl pidentd portmap ppp procmail python          \
   python-central python-newt quagga racoon radvd  sharutils squid \
   squid-common ssl-cert vlan whois iptables bind9
sudo dpkg-reconfigure locales

• Stop and disable startup of services installed:

/etc/init.d/apache2 stop
/etc/init.d/squid stop
/etc/init.d/bind9 stop
/etc/init.d/exim4 stop
/etc/init.d/lpd stop
update-rc.d -f apache2 remove
update-rc.d -f squid remove
update-rc.d -f bind9 remove
update-rc.d -f exim4 remove
update-rc.d -f lpd remove

• Set locales according to your language:

export LANGUAGE=es_ES.ISO-8859-1
export LANG=es_ES.ISO-8859-1
export LC_ALL=es_ES.ISO-8859-1
locale-gen es_ES.ISO-8859-1
apt-get install locales
dpkg-reconfigure locales

• Clean apt cache:

apt-get clean

• Set hostname:

echo vnx > /etc/hostname

• Set consoles and loopback network interface configuration:

echo '0:2345:respawn:/sbin/getty 38400 tty0' >> /etc/inittab
echo 'tty0' >> /etc/securetty 
echo 'ssh' >> /etc/securetty
echo 'auto lo' >> /etc/network/interfaces
echo 'iface lo inet loopback' >> /etc/network/interfaces

• Configure /etc/fstab:

echo 'proc         /proc          proc     defaults   0 0' >> /etc/fstab
echo 'devpts       /dev/pts       devpts   mode=0622  0 0' >> /etc/fstab
echo '/dev/ubda    /              ext4     defaults   0 1' >> /etc/fstab
echo '/dev/ubdb    /mnt/vnuml     iso9660  defaults   0 0' >> /etc/fstab

• Set root password:

passwd

• Change /etc/inittab to halt on CAD signal:

# What to do when CTRL-ALT-DEL is pressed.
ca:12345:ctrlaltdel:/sbin/shutdown -t1 -a -h now

• Create VNX specific directories:

mkdir /mnt/vnuml
mkdir /mnt/hostfs

• Create file /etc/init.d/vnxboot:

#! /bin/sh
### BEGIN INIT INFO
# Provides:          vnxboot
# Required-Start:    $remote_fs $syslog $all
# Required-Stop:
# Default-Start:     2
# Default-Stop:
# Short-Description: Run /mnt/vnuml/umlboot if it exist
### END INIT INFO

PATH=/sbin:/usr/sbin:/bin:/usr/bin

. /lib/init/vars.sh
. /lib/lsb/init-functions

do_start() {
	if [ -x /mnt/vnuml/umlboot ]; then
	        [ "$VERBOSE" != no ] && log_begin_msg "Running vnxboot (/mnt/vnuml/umlboot)"
		/mnt/vnuml/umlboot
		ES=$?
		[ "$VERBOSE" != no ] && log_end_msg $ES
		return $ES
	fi
}

case "$1" in
    start)
	do_start
        ;;
    restart|reload|force-reload)
        echo "Error: argument '$1' not supported" >&2
        exit 3
        ;;
    stop)
        ;;
    *)
        echo "Usage: $0 start|stop" >&2
        exit 3
        ;;
esac

• Give it execution permissions and enable it at startup:

chmod +x /etc/init.d/vnxboot
cd /etc/rc2.d
ln -s ../init.d/vnxboot S11vnxboot
update-rc.d vnxboot enable

• Create the /usr/local/bin/vnx_halt script:

#!/bin/bash

if [ "$1" == '-y' ]; then
    NOINTMODE='yes'
fi

# Clean apt cache
apt-get clean
apt-get -y autoremove

# Delete /etc/resolv.conf
rm -f /etc/resolv.conf

# Clean command history
rm -f /root/.bash_history

# Delete udev net rules files:
rm -f /etc/udev/rules.d/70-persistent-net.rules

if [ ! $NOINTMODE ]; then
    while true; do
        # Ask for a message to save in /etc/vnx_rootfs_version file
        echo    "** Save a log message in /etc/vnx_rootfs_version file "
        echo -n "** describing the modifications done? "
        read -n 1 -p "[y/n] " answer
        echo ""
        case $answer in
            [Yy]* )
                    echo "** Log message (1 line maximum):"
                    read logmsg
                    DATE=`date`
                    echo "MODDATE=$DATE" >> /etc/vnx_rootfs_version
                    echo "MODDESC=$logmsg" >> /etc/vnx_rootfs_version
                    break;;
            [Nn]* ) break;;
            * )     echo "** Error: please answer 'y' or 'n'.";;
        esac
    done
fi

# Check whether we are running chrooted or not
if [ ! -e /proc/1/root ]; then
  # Probably running chrooted. Do not halt!
  echo "**"
  echo "** Cannot read /proc. Probably running chrooted. Not halting"
  echo "** Type 'exit' to exit from chroot"
  exit
elif [ ! -e /proc/1/root -o "$(stat -c %d:%i /)" != "$(stat -c %d:%i /proc/1/root/.)" ]; then
  # We are chrooted! Do not halt
  echo "**"
  echo "** Running chrooted. Not halting"
  echo "** Type 'exit' to exit from chroot"
  exit
fi

# We are NOT chrooted! We halt the virtual machine
halt -p

• Give it execution permissions:

chmod +x /usr/local/bin/vnx_halt

• Create a file /etc/vnx_rootfs_version to store version number and informacion about modifications:

VER=v0.24
OS=Debian Squeeze (6.0)
DESC=Debian Squeeze root-file-system without GUI

• Create /dev/ubd* devices:

cd /dev
mknod --mode=660 ubda b 98 0
mknod --mode=660 ubdb b 98 0
chown root:disk ubda        
chown root:disk ubdb

• Clean caches and history files and optionally leave a description message /etc/vnx_rootfs_version file:

vnx_halt

• Exit chroot: exit
• Install kernel modules:

cd mnt/lib/modules/
tar xfv /usr/share/vnx/kernels/linux-3.3.8-um-src/modules-3.3.8.tar 
cd ../../../

• Umount rootfs to finish installation:

umount mnt/proc/
umount mnt

Note: if you cannot umount 'mnt' directory, check which process is blocking the unmounting operation with 'lsof mnt' and stop it.

Optional

Install VNXACED if you plan to use command execution based on 'sdisk' mode:

• Mount the rootfs:

mount -o loop vnx_rootfs_uml_debian-6.0-v024c.img /mnt

• Copy vnxaced tar file:

cp /usr/share/vnx/aced/vnx-aced-lf-2.0b.2487.tgz /mnt/tmp

• chroot to rootfs and install:

chroot /mnt
apt-get -y install libxml-libxml-perl
cd /tmp
tar xfvz vnx-aced-lf-2.0b.2487.tgz
LC_ALL=C perl vnx-aced-lf-2.0b.2487/install_vnxaced
cd /mnt 
ln -s hostfs sdisk

• Edit /usr/local/bin/vnxaced and change:

use constant H2VM_CHANNEL => 'SERIAL';
use constant MOUNT => 'YES';

to:

use constant H2VM_CHANNEL => 'SHARED_FILE';
use constant MOUNT => 'NO';

• Finish:

exit
umount /mnt

Installing additional software

There is two basic ways to update a UML root filesystems:

A. Starting a virtual machine that mounts the rootfs in direct mode:

• Create a VNX scenario named, for example, update_uml.xml (available in /usr/share/vnx/examples):

<?xml version="1.0" encoding="UTF-8"?>
<!--
~~~~~~~~~~~~~~~~~~~~
VNX Sample scenarios
~~~~~~~~~~~~~~~~~~~~
Name:        update_uml
Description: Simple scenario to start a uml virtual machine in direct mode to make modifications 
             in a filesystem. Tha VM is connected to virbr0, the default network used by libvirt, 
             to gain network connectivity.

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>update_uml</scenario_name>
    <automac/>
    <vm_mgmt type="none" />
    <vm_defaults>
        <exec_mode type="uml">mconsole</exec_mode>
    </vm_defaults>
  </global>

  <net name="virbr0" mode="virtual_bridge" />

  <vm name="uml" type="uml" subtype="" os="">
    <filesystem type="direct">ROOTFS_PATHNAME</filesystem>
    <mem>64M</mem>
    <kernel trace="on">UML_KERNEL</kernel>
    <console id="0" display="yes">xterm</console>
    <if id="1" net="virbr0">
    </if>
    <exec seq="on_boot" type="verbatim">dhclient eth1</exec>
  </vm>

</vnx>

Change ROOTFS_PATHNAME and UML_KERNEL by the full pathname of the root filesystem to be modified and the UML kernel to be used to start it.

• Start the virtual machine with:

vnx -f update_uml.xml -v -t

• Once started, check that the virtual machine has network connectivity. If not, try to configure it with:

dhclient eth1

• Do the installations or modifications desired
• Finally, clean caches and history files and, optionally, leave a message describing the modifications done (saved to /etc/vnx_rootfs_version file), befor halting the virtual machine:

vnx_halt

B. Mounting the rootfs and chrooting to it:

• Mount the rootfs:

mkdir mnt
mount -o loop vnx_rootfs_uml_debian.img mnt/
mount -t proc none mnt/proc

• Chroot:

chroot mnt
env -update

• Check you have network connectivity. You'll probably have to modify /etc/resolv.conf file to configure DNS server IP address
• Modify the rootfs
• Clean caches and history files and optionally leave a message describing the modifications done (saved to /etc/vnx_rootfs_version file:

vnx_halt

• Exit chroot an umount:

exit
umount mnt/proc
umount mnt

Note: if you cannot umount 'mnt' directory, check which process is blocking the unmounting operation with 'lsof mnt' and stop it.

Installing kernel modules

When you change or update the kernel you are using with a root filesystem, you have to copy the new kernel modules to the root filesystem:

mount -o loop vnx_rootfs_uml_debian.img mnt
cd mnt/lib/modules/
tar xfv /usr/share/vnx/kernels/linux-3.3.8-um-src/modules-3.3.8.tar 
cd ../../../ 
umount mnt/