Vnx-rootfscentos

How to create a KVM CentOS root filesystem for VNX

Basic installation

Follow this procedure to create a KVM CentOS based root filesystem for VNX. The procedure has been tested with CentOS 5.6, 6.2, 6.4, 6.5 and 7.0.

• Create the filesystem disk image:

qemu-img create -f qcow2 vnx_rootfs_kvm_centos.qcow2 20G

• Get CentOS installation DVD (we recommend to use the complete DVD; the LiveDVD version does not include the customization menu to choose among different installation profiles: minimal, desktop, etc). For example:

wget ftp://ftp.rediris.es/mirror/CentOS/X.X/isos/i386/CentOS-X.X-i386-bin-DVD1.iso
cp CentOS-X.X-i386-bin-DVD1.iso /almacen/iso

Note: latests versions of CentOS are distributed in two DVDs. However, only the first DVD is needed for basic installations; no need to download DVD2.

• Create the virtual machine with:

vnx --create-rootfs vnx_rootfs_kvm_centos.qcow2 --install-media /almacen/iso/CentOS-X.X-i386-bin-DVD1.iso --mem 768M

Note: around 768M of memory are needed to use the graphical installation assistant. With the textual assistant the memory requirements are lower (known to work with 512M).

Note: add "--arch x86_64" option for 64 bits virtual machines

• Follow the CentOS installation assistant. At some point, you will have to choose among different system profiles: Desktop, Minimal Desktop, Minimal, Basic Server, etc.
• Once the installation is finished and the installer asks for rebooting the system, just stop the virtual machine using "virsh destroy ..." command and continue with the configuration phase.

Configuration

• Restart the system with the following command:

vnx --modify-rootfs vnx_rootfs_kvm_centos.qcow2 --update-aced --mem 768M

Note: ignore the errors "timeout waiting for response on VM socket". Note2: 768M are needed if you are installing a root filesystem with desktop interface; 512M are enough for a text version.

• Configure the serial console:
• For CentOS 5.X and 6.X, following these instructions.
• For CentOS 7.X, by executing:

grubby --update-kernel=ALL --args="console=ttyS0"

• Delete the net udev rules file and reboot the system:

rm /etc/udev/rules.d/70-persistent-net.rules
halt

• Once started, access the system through the text console to easy the copy-paste of commands:

virsh console vnx_rootfs_kvm_centos.qcow2

• Check that you have network connectivity. Maybe you have to activate the network interface by hand:

dhclient eth1

Note: use "ip link show" to know which network interface to use.

• Configure the RPMForge repository following the procedure described here:

yum install wget
wget http://pkgs.repoforge.org/rpmforge-release/rpmforge-release-0.5.3-1.el6.rf.i686.rpm
rpm --import http://apt.sw.be/RPM-GPG-KEY.dag.txt
rpm -K rpmforge-release-0.5.3-1.el6.rf.*.rpm
rpm -i rpmforge-release-0.5.3-1.el6.rf.*.rpm

Note: change 'i686' by 'x86_64' for 64 bits root filesystems.

• Install daemonize package (available from repoforge):

yum install daemonize

• Update the system and install additional packages

yum update
yum install perl perl-XML-LibXML perl-NetAddr-IP acpid perl-Sys-Syslog

Note: if you get a dependencies error when installing LibXML package, try installing 'perl-XML-SAX' package instead.

• Install VNX autoconfiguration daemon:

mount /dev/sdb /mnt/
perl /mnt/vnxaced-lf/install_vnxaced

• Optionally:
• Disable the services you are not going to use to speed up the virtual machine startup (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 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

• Or, if using a "minumum installation", install network utilities:

yum install telnet wget openssh-clients traceroute tcpdump

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

VER=v0.25
OS=CentOS 6.5
DESC=Basic CentOS 6.5 root-filesystem without GUI

• Finally, stop the virtual machine with:

vnx_halt

vnx_halt deletes some caches and log files and optionally lets you write a short message to /etc/vnx_rootfs_version file describing the latest modifications done.

Installing additional software

To install additional software or to modify your root file system, you just have to:

• Start a virtual machine from it:

vnx --modify-rootfs vnx_rootfs_kvm_centos.qcow2

• Check network connectivity. Maybe you have to activate the network interface by hand:

dhclient eth1

Note: use "ip link show" to know which network interface to use.

• Do the modifications you want.
• Finally, halt the system using:

vnx_halt

Updating VNXACED

You can automatically update the VNXACE daemon with the following command:

vnx --modify-rootfs vnx_rootfs_kvm_centos.qcow2 --update-aced -y

Known issues

• When executing commands using vnx "--exe" option in virtual machines configured with exec_mode="cdrom", 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.