Vnx-rootfscentos

How to create a CentOS root filesystem for VNX

Basic installation

Follow this procedure to create a CentOS based root filesystem for VNX. The procedure has been tested with CentOS 5.6.

• Create the filesystem disk image:

qemu-img create -f qcow2 vnx_rootfs_centos-base.qcow2 5GB

• Get CentOS installation DVD (use the complete DVD; do not use the Live version, as it seems the installation wizard does not include the customization menu). For example:

wget http://ftp.gui.uva.es/sites/centos.org/5.6/isos/i386/CentOS-5.6-i386-bin-DVD.iso
cp CentOS-5.6-i386-bin-DVD.iso /almacen/iso

• Create a libvirt XML definition (rootfs_centos.xml) containing the virtual machine description:

<domain type='kvm'>
  <name>CentOS</name>
  <memory>524288</memory>
  <vcpu>1</vcpu>
  <os>
    <type arch="i686">hvm</type>
    <boot dev='hd'/>
    <boot dev='cdrom'/>
  </os>
  <features>
     <pae/>
     <acpi/>
     <apic/>
  </features>
  <clock sync="localtime"/>
  <devices>
    <emulator>/usr/bin/kvm</emulator>
    <disk type='file' device='disk'>
      <source file='/usr/share/vnx/filesystems/vnx_rootfs_centos-base.qcow2'/>
      <target dev='hda'/>
    </disk>
    <disk type='file' device='cdrom'>
      <source file='/almacen/iso/CentOS-5.6-i386-bin-DVD.iso'/>
      <target dev='hdb'/>
    </disk>
    <interface type='network'>
      <source network='default'/>
    </interface>
    <serial type="pty">
      <target port="1"/>
    </serial>
    <console type="pty">
      <target port="1"/>
    </console>
    <graphics type='vnc'/>
  </devices>
</domain>

Note: change "source file=" lines to whatever fits your case (use full paths).

• Start the virtual machine with:

virsh create rootfs_centos.xml

• Access virtual machine console with:

virt-viewer CentOS

• Follow CentOS installation menus to install:
• A "minimal" system, if you want a server rootfs without user interface
• One of the other options (e.g "web server", "desktop system", etc) if you want a system with graphical user interface

Configuration

• Once installation is finished, configure the RPMForge repository following the procedure described here:

wget http://packages.sw.be/rpmforge-release/rpmforge-release-0.5.2-2.el5.rf.i386.rpm
rpm --import http://apt.sw.be/RPM-GPG-KEY.dag.txt
rpm -K rpmforge-release-0.5.2-2.el5.rf.*.rpm
rpm -i rpmforge-release-0.5.2-2.el5.rf.*.rpm

• Update the system and install additional packages

yum update
yum install perl perl-XML-DOM perl-XML-Parser acpid daemonize

• Install VNX autoconfiguration daemon:
• From the host execute:

/usr/share/vnx/bin/vnx_update_aced CentOS /usr/share/vnx/aced/vnx-aced-lf-0.1b.tgz 

• From the virtual machine console:

mkdir /media/cdrom
mount /dev/cdrom /media/cdrom
perl /media/cdrom/install_vnxdaemon

• Configure the serial console following these instructions.
• Disable the services you are not going to use (you can see the list of active services with "chkconfig --list"). For example to disable sendmail and bluetooth:

chkconfig sendmail off
chkconfig bluetooth off

• Disable eth0 autoconfiguration to avoid delays at startup. Edit /etc/sysconfig/network-scripts/ifcfg-eth0 file and change "ONBOOT" line to:

ONBOOT=no

• Optionally:
• Disable the firewall. Firewall is enabled by default which could be problematic for testing purpose systems. If desired, disable it using the following command:

chkconfig iptables off
chkconfig ip6tables off

• Enable IPv6 by deleting the following lines in /etc/modprobe.conf:

alias ipv6 off
options ipv6 disable=1

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

VER=v0.21
OS=CentOS 5.6
DESC=Basic CentOS 5.6 root-filesystem without GUI

• Create a script named /usr/local/bin/vnx_halt:

#!/bin/bash
echo "** Cleaning yum cache..."
yum clean all
echo "** Deleting /etc/resolv.conf..."
rm -f /etc/resolv.conf
echo "** Cleaning command history...."
rm -f /root/.bash_history
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
echo ""
echo "** Halting the system..."
halt

• Give the script execution permissions:

chmod +x /usr/local/bin/vnx_halt

• Stop the machine with that script:

vnx_halt

Installing additional software

To install additional software or modify your root file system, you just have to start it as described above and make the operations required on the filesystem.

• Start the virtual machine (directly using virsh or the vnx_modify_rootfs utility):

 /usr/share/vnx/bin/vnx_modify_rootfs rootfs_centos.xml 

• Install the software:

yum install ...

• Stop the machine with:

vnx_halt

Known issues

• When executing commands using vnx "--exe" option, traces like the followinf appear on the consoles:

hdb: tray open
end_request: I/O error, dev hdb, sector 8388352

They are generated as a result of mount command execution by the VNX daemon. Commands are correctly executed. To be further investigated.