Grant McWilliams

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Saturday, 14 January 2012 01:34

CentOS 6 virtual machine (32 bit) installation on XCP

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Introduction

This tutorial was written in the spirit of my CentOS 6 virtual machine (32 bit) installation on Xen howto which was based on the CentOS 5 version of the same. In those tutorials I created a disk, downloaded a kernel, kickstart file plus a xen config file which installed CentOS using the kickstart file. This has proven very popular since you can't install a paravirtualized domain using an install disk. This has been a very nice installation howto because you don't have to download any install CD/DVDs and you could create VMs using nothing more than a commandline login. It's also very nice because it can be mirrored locally if you're doing a bunch of them just by rsyncing a CentOS mirror locally then downloading my files and editing them.

I've recently migrated a lot of my XEN systems to Xen Cloud Platform and it's a very different animal indeed. However, I still needed a system of creating CentOS Virtual Machines in that same manner. I didn't want to download a CentOS install DVD or need a graphical login to install the OS thus this tutorial was born.

It uses the very same CentOS 6 kickstart file from my site as the Xen tutorial. It also uses the very same CentOS 6 repositories on the Internet so in a lot aspects it IS the same tutorial crafted for XCP but will be a bit shorter.

 More after the jump.

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Sunday, 25 December 2011 19:36

How to create custom XCP templates

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Creating a template

The following is how to create new custom templates based on existing templates in Xen Cloud Platform. 

1. Get the template UUID that we want to use as our base. As usual just copy and paste the line in yellow into a root terminal on your XCP host.

xe template-list | grep -B1 name-label | awk -F: '{print $2}'

The output should look like this..

 

 688c625b-93b8-8e66-62e5-4542eca1e597

 Red Hat Enterprise Linux 6 (32-bit)

 

 c4e28252-030f-524a-c5d8-7da85df3ccf5

Windows Server 2003 (64-bit)

......

 

Scroll through the list and find the template you want to clone then copy and past it's UUID number ie.  688c625b-93b8-8e66-62e5-4542eca1e597. Choose a new name for your custom template and enter the following line with the UUID of the template you want to clone and the name you want it to have.

 

xe vm-clone uuid=<UUID> new-name-label="<NAME>"
xe template-param-set uuid=<UUID> other-config:install-methods=http,ftp,nfs other-config:default_template=true

Now you should have a new template of your own that you can customize. More after the jump.

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Tuesday, 20 December 2011 16:00

Fix XCP expired license issue

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If you're running virtually any version of Xen Cloud Platform you may have run into this error message.

Your license has expired.  Please contact your support representative.

It's not really possible to have an expired license on Xen Cloud Platform (XCP) since it's FREE. It's just a regressive bug that has been very stubborn. However, until they fix it for real in XCP 1.5 you'll need follow the steps below.  

Open a root terminal on the XCP host and copy and paste the commands below.

 

service xapi stop;sleep 5
NEXTMONTH=`date --date="next Month" '+%Y%m%d'`
sed -i "s/\(expiry.\{3\}\)[0-9]\{8\}/\1$NEXTMONTH/g" /var/xapi/state.db
service xapi start
echo done

 

The last line is only to get all the important lines to run automatically. If you don't hit enter it doesn't hurt anything.  You could also copy and paste these lines into a script and have it run as a cronjob. Because XCP doesn't like you bumping it's "evaluation license" out more than 30 days you might want to run the cronjob once a week to make sure your license doesn't lapse while you're waiting for the cronjob to run

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Thursday, 17 November 2011 09:55

CentOS 6 virtual machine (64 bit) installation on XCP

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Introduction

This tutorial was written in the spirit of my CentOS 6 virtual machine (64 bit) installation on Xen howto which was based on the CentOS 5 version of the same. In those tutorials I created a disk, downloaded a kernel, kickstart file plus a xen config file which installed CentOS using the kickstart file. This has proven very popular since you can't install a paravirtualized domain using an install disk. This has been a very nice installation howto because you don't have to download any install CD/DVDs and you could create VMs using nothing more than a commandline login. It's also very nice because it can be mirrored locally if you're doing a bunch of them just by rsyncing a CentOS mirror locally then downloading my files and editing them.

I've recently migrated a lot of my XEN systems to Xen Cloud Platform and it's a very different animal indeed. However, I still needed a system of creating CentOS Virtual Machines in that same manner. I didn't want to download a CentOS install DVD or need a graphical login to install the OS thus this tutorial was born.

It uses the very same CentOS 6 kickstart file from my site as the Xen tutorial. It also uses the very same CentOS 6 repositories on the Internet so in a lot aspects it IS the same tutorial crafted for XCP but will be a bit shorter.

 

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Thursday, 13 October 2011 17:47

Creating an iSCSI target on Xen Cloud Platform 1.1

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Creating an iSCSI target on Xen Cloud Platform 1.1

Premise: I have two pools – The first has one host in it that acts as a router, firewall and Host for a couple of special VMs for (DNS, DHCP, NFS, Web) the hosts in a second pool. I've added iSCSI SAN to it's lists of jobs using a software iSCSI target in the 8 steps below.


1. Install tgt from CentOS repos

[root@cloud0 ~]# yum --enablerepo=base install scsi-target-utils

2. Start the tgt service

[root@cloud0 ~]# service tgtd start

[root@cloud0 ~]# chkconfig tgtd on

3. Preparing for LVM

 

I'm using a separate hard drive - /dev/sdb and creating one partition which will be used as my LVM Physical Volume. We'll then add it to the Volume Group and carve it up into Logical Volumes. This way I can just add another hard drive to the Volume Group when we want more capacity and the rest of the tutorial stays the same. The bold letters are what I input, I accepted the defaults everywhere else.

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Wednesday, 27 July 2011 18:22

Updated Xen Howtos

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There's been a flurry of activity around The Man, The Myth, The Legend in the Xen Howtos section and for good reason - CentOS6 was released. It all started as a simple update to my installation tutorials but ultimately I spent half a week on it. There were some issues with how I was doing things because CentOS5 used the old Xen kernel and CentOS6 uses the new libvirt kernel. As of RHEL5/CentOS6 Xen Host (dom0) support is no longer in the kernel. However, Xen Guests (DomU) is and  is handled by libvirt. Last week the last bits of Xen Dom0 support were merged into Linux Kernel 3.0. This means that going forward all Linux distributions will have Xen Dom0 ability unless the distributors remove it.

I've written and tested two xen tutorials this week.

During the process of writing these tutorials I shrunk the size of the Disk Image. I did this because I like nice small VM disk images (and sparse too) so I can duplicate them and move them around easily. It's fairly easy to resize a disk image so I updated all four tutorials on how to resize Dom0 Disk Images and Logical Volumes as well as DomU Logical Volumes and partitions. I attempted to make it clearer too what the scenario was so people would know what the tutorial was trying to accomplish.

As always have lots of fun and let me know if something doesn't work via the comments.

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Sunday, 24 July 2011 16:36

Centos 6 virtual machine (32 bit) installation on Xen

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Introduction

A lot of this tutorial was stolen from my CentOS 5 Installation which in turn was stolen from the CentOS wiki. I've shortened and updated it for installing a CentOS 6 DomU. I just copy and paste all the indented lines into a root terminal and voila! a CentOS VM.

1. Creating an Virtual Disk Image

The first step is to create an disk image that will act as the VM hard drive. The following command will create a 4 GB sparse disk image named /srv/xen/centos6.img. A sparse file is created in such a way that the disk image doesn't actually take up the whole 4GB until you fill it up. If you'd like a larger (11GB) disk image substitute seek=10240 into the following line. I make my VMs nice and small so I can move them around easier. Making a disk image larger or adding a second drive later is easier than making it smaller or taking a drive away.

 

dd if=/dev/zero of=/srv/xen/centos6.img oflag=direct bs=1M seek=3800 count=1

2. Preparing the Xen configuration file for installation

Xen uses one configuration file per VM. We will start out with a config to do the install and replace it later with a config for normal operation. Now we download the install kernel, ramdisk and xen config file.

wget http://mirror.centos.org/centos/6/os/i386/isolinux/vmlinuz -O /boot/vmlinuz-xen6-install
wget http://mirror.centos.org/centos/6/os/i386/isolinux/initrd.img -O /boot/initrd-xen6-install
wget http://www.grantmcwilliams.com/files/centos6-install -O /etc/xen/centos6

 

 

 

3. Starting the installation

A kickstart file holds instructions for automatic installation and is referenced in my xen config above. My example kickstart file is very minimal but is enough to get a working CentOS 6 VM.

 

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Sunday, 24 July 2011 16:36

Centos 6 virtual machine (64 bit) installation on Xen

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Introduction

A lot of this tutorial was stolen from my CentOS 5 Installation which in turn was stolen from the CentOS wiki. I've shortened and updated it for installing a CentOS 6 DomU. I just copy and paste all the indented lines into a root terminal and voila! a CentOS VM.

1. Creating an Virtual Disk Image

The first step is to create an disk image that will act as the VM hard drive. The following command will create a 4 GB sparse disk image named /srv/xen/centos6.img. A sparse file is created in such a way that the disk image doesn't actually take up the whole 4GB until you fill it up. If you'd like a larger (11GB) disk image substitute seek=10240 into the following line. I make my VMs nice and small so I can move them around easier. Making a disk image larger or adding a second drive later is easier than making it smaller or taking a drive away.

 

dd if=/dev/zero of=/srv/xen/centos6.img oflag=direct bs=1M seek=3800 count=1

2. Preparing the Xen configuration file for installation

Xen uses one configuration file per VM. We will start out with a config to do the install and replace it later with a config for normal operation. Now we download the install kernel, ramdisk and xen config file.

wget http://mirror.centos.org/centos/6/os/x86_64/isolinux/vmlinuz -O /boot/vmlinuz-xen6-install
wget http://mirror.centos.org/centos/6/os/x86_64/isolinux/initrd.img -O /boot/initrd-xen6-install
wget http://www.grantmcwilliams.com/files/centos6_64-install -O /etc/xen/centos6

 

 

 

 

 

 

 

3. Starting the installation

A kickstart file holds instructions for automatic installation and is referenced in my xen config above. My example kickstart file is very minimal but is enough to get a working CentOS 6 VM.

 

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Saturday, 19 June 2010 12:33

Install Xen 3.4 on CentOS5 (64bit) the easy way

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1. First we need to download the YUM repository file for the updated Xen. Then uninstall the old Virtualization group and reinstall it. This will upgrade the packages.

wget http://www.gitco.de/linux/x86_64/centos/5/CentOS-GITCO.repo -O /etc/yum.repos.d/gitco.repo
yum groupremove Virtualization
yum groupinstall -y Virtualization

Yum will probably want to upgrade some other files along with the ones we've chosen.

Warning! If you get an error message from grubby this is bad!

Installing: kernel-xen                   ####################### [ 9/13]
grubby fatal error: unable to find a suitable template

This means that your grub.conf file couldn't be written to for whaterver reason so you won't be able to successfully reboot. If you get this message you need to edit your /boot/grub/grub.conf file and make the kernel lines match the kernel you installed.

Get your installed kernel version:

[ root@vs / ] rpm -q kernel-xen

kernel-xen-2.6.18-128.4.1.el5

Now edit your /boot/grub/grub.conf to match this

# grub.conf generated by anaconda
#
# Note that you do not have to rerun grub after making changes to this file
# NOTICE:  You have a /boot partition.  This means that
#          all kernel and initrd paths are relative to /boot/, eg.
#          root (hd0,0)
#          kernel /vmlinuz-version ro root=/dev/vgsys/lvroot
#          initrd /initrd-version.img
#boot=/dev/sda
default=0
timeout=5
splashimage=(hd0,0)/grub/splash.xpm.gz
hiddenmenu
title CentOS (2.6.18-128.4.1.el5xen)
root (hd0,0)
kernel /xen.gz-3.4.0
module /vmlinuz-2.6.18-128.4.1.el5xen ro root=/dev/vgsys/lvroot rhgb quiet
module /initrd-2.6.18-128.4.1.el5xen.img

4. Reboot - no really I mean it.

5. Try it out by using the xm dmesg command

\ \/ /___ _ __   |___ / |___ / / _ \
\  // _ \ '_ \    |_ \   |_ \| | | |
/  \  __/ | | |  ___) | ___) | |_| |
/_/\_\___|_| |_| |____(_)____(_)___/

(XEN) Xen version 3.3.0 ( This email address is being protected from spambots. You need JavaScript enabled to view it. ) (gcc version 4.1.2 20071124 (Red Hat 4.1.2-42)) Tue Sep  9 20:18:14 CEST 2008
(XEN) Latest ChangeSet: unavailable
(XEN) Command line:
(XEN) Video information:
(XEN)  VGA is text mode 80x25, font 8x16
(XEN)  VBE/DDC methods: V2; EDID transfer time: 2 seconds
(XEN) Disc information:
(XEN)  Found 1 MBR signatures
(XEN)  Found 1 EDD information structures
(XEN) Xen-e820 RAM map:

That's about all. If you have any questions drop a comment here.

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Thursday, 24 September 2009 10:00

Getting Started with Xen

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I'm using a Xen Virtual Server to provide my Linux students with their own machines with admin rights. This has prompted interest in Xen from a lot of people just starting out in Virtualization. Following is a quick explaination of Xen and how to get a Virtual Machine up and running as fast as possible.

Hypervisors

Xen is a hypervisor meaning that it runs above the hardware but below any OS. Traditionally when you "virtualized" an OS you'd have a computer that you logged into which you installed virtualization software on such as VMWare workstation or VirtualBox. With this software you'd start the Virtual Machine from it's GUI and install the Guest OS via CDROM. In this case you have a Host Machine (the real physical machine) and a Guest Machine (the virtualized OS). With a hypervisor ALL operating systems are virtualized. This might seem a bit strange or impossible but is very powerful and extremely effecient. The side effect is that Xen can be very complex to set up. Let me explain the Xen boot process.

Xen Boot Process

  1. Machine runs code in Master Boot Record
  2. Bootloader loads the OS kernel
  3. Xen lodges itself in memory and loads the rest of the kernel in a Virtual Machine
  4. The user logs into the first Virtual Machine and starts, stops and restarts the other Virtual Machines from there

The name for the first Virtual Machine is Dom0 - it's the privileged Domain so it has direct access to the physical hardware. All subsequent Virtual Machines that are started are called DomU - unprivileged Domains. To manage a Xen Virtual Server you log into the Privileged Domain (Dom0) and use various commands to administer the Unprivileged Domains (DomUs).

Two modes of Virtualization

Virtualizers work in one of two modes - paravirtualization or hardware (full) virtualization. The difference being that a paravirtualized DomU OS knows it's being virtualized and has extensions to allow and assist in this. Paravirtualized Operating Systems are very fast and effecient. However there are times when you won't be virtualizing an OS that has these extensions such as Windows. In this case you need to use a CPU that has hardware vitualization support and run Xen in HVM (Hardware Virtualization Mode).

Paravirtualization:

  • Runs on a lot of hardware - x86, x86-64, Itanium and PowerPC 970 with or without hardware Virtualization support
  • DomUs can be Linux, NetBSD and Solaris
  • Very fast

Full Virtualization:

  • Requires Intel or AMD cpus with Virtualization Support built in
  • DomUs can be most any unmodified OS including Windows
  • Not so fast

To get around the speed issues with Full Virtualization there are paravirtualized drivers that have been written for many Operating Systems including Windows for disk access and network cards. This allows Full Virtualization to reach the speeds of paravirtualization in these two areas without requiring further modification to the Operating System. The Linux KVM Hypervisor runsin Full Virtualization mode all the time and thus needs paravirtualized drivers.

 

 

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