Grant McWilliams

XCP and Xenserver store their Virtual Disk Images on storage repository. To see how much space you have on your LVM or lvmoisci storage repositories from the commandline can be quite a chore so I wrote a df command for storage repositories. My dfsr command mimics the output of the Linux df command with the human readable flag set (-h). All values will be printed in Kilobytes, Megabytes, Gigabytes and so on. It shows the size of the repository, how much is used, how much is available, the percent used and the Storage Repository type. 

 Get it from my Virtualization downloads section.

 On occasion you may want to have access to a VM's Virtual Disk Image from the Control Domain (or another VM). An example of this would be access files in a VM disk that due to corruption will no longer boot. An XCP local Storage Repository is created from an LVM Volume Group. Each Virtual Disk Image represents one Logical Volume. However, mounting the Logical Volume directly isn't possible because there's  VHD (Virtual Hard Drive) container inside the Logical Volume. Inside the VHD is the real VM disk's partitions. The hierarchy goes something like this  Control Domain Volume Group -> Control Domain Logical Volume -> VHD Container -> VM disk -> VM disk physical Volume -> VM Disk Volume Group -> VM Disk Logical Volume -> VM Disk filesystem. You can see there's quite a few layers here but mounting the VM's disk filesystem IS possible. Here's how.

Since the Control Domain is really a VM itself (privileged VM) we can create a Virtual Block Device using the VM's Virtual Disk Image. From there we use kpartx to map the partitions to Control Domain device nodes.

1. Finding VDI UUID number

[root@testcloud1 ~]# xe vbd-list
uuid ( RO)             : b68a332b-4155-f1c4-b224-18fb465dc8e4
          vm-uuid ( RO): fec94868-0449-3616-39b9-08c3b27dab70
    vm-name-label ( RO): Fedora17
         vdi-uuid ( RO): 199619f0-e483-4618-bbd4-bdc9c524bde1
            empty ( RO): false
           device ( RO): 

2. Finding the Control Domain UUID number 

[root@testcloud1 ~]# xe vm-list is-control-domain=true
uuid ( RO)           : 2dfc3f33-4afa-47dd-8af6-21877326f8e4
     name-label ( RW): Control domain on host: testcloud1
    power-state ( RO): running

3. Creating a virtual block device for the VDI on our Control Domain. This returns the VBD UUID. 

[root@testcloud1 ~]# xe vbd-create device=autodetect vm-uuid=2dfc3f33-4afa-47dd-8af6-21877326f8e4   vdi-uuid=199619f0-e483-4618-bbd4-bdc9c524bde1
11740055-f8d4-3d84-1f90-fb1f4b646fd6

4. Plugging in the Virtual Block Device gives us a /dev/sm/backend/<sr-uuid>/<vdi-uuid> device which fdisk will list. 

[root@testcloud1 ~]# xe vbd-plug uuid=11740055-f8d4-3d84-1f90-fb1f4b646fd6 

5. Showing the VBD attached to the control domain AND to the Fedora17 VM 

[root@testcloud1 ~]# xe vbd-list 
uuid ( RO)             : b68a332b-4155-f1c4-b224-18fb465dc8e4
          vm-uuid ( RO): fec94868-0449-3616-39b9-08c3b27dab70
    vm-name-label ( RO): Fedora17
         vdi-uuid ( RO): 199619f0-e483-4618-bbd4-bdc9c524bde1
            empty ( RO): false
           device ( RO): 


uuid ( RO)             : 11740055-f8d4-3d84-1f90-fb1f4b646fd6
          vm-uuid ( RO): 2dfc3f33-4afa-47dd-8af6-21877326f8e4
    vm-name-label ( RO): Control domain on host: testcloud1
         vdi-uuid ( RO): 199619f0-e483-4618-bbd4-bdc9c524bde1
            empty ( RO): false
           device ( RO): sm/backend/ec2eb4df-040c-2a75-1c9f-69b953ac9e8d/199619f0-e483-4618-bbd4-bdc9c524bde1

6. Showing the Device Node using ls and fdisk

[root@testcloud1 ~]# ls -l /dev/sm/backend/ec2eb4df-040c-2a75-1c9f-69b953ac9e8d/199619f0-e483-4618-bbd4-bdc9c524bde1
brw------- 1 root root 253, 0 Jan 12 00:52 /dev/sm/backend/ec2eb4df-040c-2a75-1c9f-69b953ac9e8d/199619f0-e483-4618-bbd4-bdc9c524bde1

[root@testcloud1 ~]# fdisk -l $(ls /dev/sm/backend/ec2eb4df-040c-2a75-1c9f-69b953ac9e8d/199619f0-e483-4618-bbd4-bdc9c524bde1)

Disk /dev/sm/backend/ec2eb4df-040c-2a75-1c9f-69b953ac9e8d/199619f0-e483-4618-bbd4-bdc9c524bde1: 8589 MB, 8589934592 bytes
255 heads, 63 sectors/track, 1044 cylinders
Units = cylinders of 16065 * 512 = 8225280 bytes

                                                                                     Device Boot      Start         End      Blocks   Id  System
/dev/sm/backend/ec2eb4df-040c-2a75-1c9f-69b953ac9e8d/199619f0-e483-4618-bbd4-bd  *           1         980     7863296   83  Linux
Partition 1 does not end on cylinder boundary.
/dev/sm/backend/ec2eb4df-040c-2a75-1c9f-69b953ac9e8d/199619f0-e483-4618-bbd4-bd            980        1045      524288   82  Linux swap / Solaris
[root@testcloud1 ~]# kpartx -a $(ls /dev/sm/backend/ec2eb4df-040c-2a75-1c9f-69b953ac9e8d/199619f0-e483-4618-bbd4-bdc9c524bde1)
[root@testcloud1 ~]# ls /dev/mapper/
199619f0-e483-4618-bbd4-bdc9c524bde1p1
199619f0-e483-4618-bbd4-bdc9c524bde1p2
control
VG_XenStorage--ec2eb4df--040c--2a75--1c9f--69b953ac9e8d-MGT
VG_XenStorage--ec2eb4df--040c--2a75--1c9f--69b953ac9e8d-VHD--199619f0--e483--4618--bbd4--bdc9c524bde1
VG_XenStorage--ec2eb4df--040c--2a75--1c9f--69b953ac9e8d-VHD--6c663b1b--d9c4--45bd--9071--3f6b4668d164

7. Use kpartx to create /dev/mapper entries for each partition.

[root@testcloud1 ~]# kpartx -a $(ls /dev/sm/backend/ec2eb4df-040c-2a75-1c9f-69b953ac9e8d/199619f0-e483-4618-bbd4-bdc9c524bde1)

8. kpartx creates /dev/mapper nodes

[root@testcloud1 ~]# ls /dev/mapper/
199619f0-e483-4618-bbd4-bdc9c524bde1p1
199619f0-e483-4618-bbd4-bdc9c524bde1p2
control
VG_XenStorage--ec2eb4df--040c--2a75--1c9f--69b953ac9e8d-MGT
VG_XenStorage--ec2eb4df--040c--2a75--1c9f--69b953ac9e8d-VHD--199619f0--e483--4618--bbd4--bdc9c524bde1
VG_XenStorage--ec2eb4df--040c--2a75--1c9f--69b953ac9e8d-VHD--6c663b1b--d9c4--45bd--9071--3f6b4668d164

9. Mount the partitions

[root@testcloud1 ~]# mount /dev/mapper/199619f0-e483-4618-bbd4-bdc9c524bde1p1 /media/Fedora17-rootfs/

[root@testcloud1 ~]# ls /media/Fedora17-rootfs/
bin  boot  dev  etc  home  lib  lib64  lost+found  media  mnt  opt  proc  root  run  sbin  srv  sys  tmp  usr  var

Notes: Be careful with mounting VDI's from VMs on the Control Domain. Best practice is to make sure that the VDI is not accessible from the Control Domain AND the VM at the same time. Mounting to two locations at once is a great way of corrupting your disk by having two different Operating Systems writing to the disk at the same time.

Prerequisites

• XCP/Xenserver

Adding a CD to a running VM is not a difficult task if you know which commands to use. By adding I mean we're going to insert a virtual CD disk into a virtual machine using our little virtual hands. ;-)

1. Get the name of your Virtual Machine

In this case the name is CentOS6 and the UUID is cefb9f88-0424-6701-5ba1-070490c69203.

[ root@cloud2 ~/bin ] xe vm-list
     uuid ( RO)           : cefb9f88-0424-6701-5ba1-070490c69203
          name-label ( RW): CentOS6
         power-state ( RO): running

2. Get the name of the CD disk

In this case our disk is named CentOS-6.3-x86_64-LiveCD.iso.

[ root@cloud2 ~/bin ] xe cd-list
    uuid ( RO)          : 0549c68a-e38d-4cd8-9974-ba0b9167ff5a
        name-label ( RW): CentOS-6.3-x86_64-LiveCD.iso

3. Identify a free Virtual Block Device number

Use the VM UUID that we retrieved in step 1.

[ root@cloud2 ~/bin ] xe vm-param-get uuid=cefb9f88-0424-6701-5ba1-070490c69203 \
 param-name=allowed-VBD-devices
5; 6; 7; 8; 9; 10; 11; 12; 13; 14; 15

4. Add the CD to the VM. Use the VM UUID from step 1, the CD name from step 2 and the VBD device number from step 3.

[ root@cloud2 ~/bin ] xe vm-cd-add uuid=cefb9f88-0424-6701-5ba1-070490c69203 \
  device=5 cd-name=CentOS-6.3-x86_64-LiveCD.iso 

5. Verify using xe vm-cd-list

 By using xe vm-cd-list we can list the CD's currently plugged into our VM.

[ root@cloud2 ~/bin ] xe vm-cd-list uuid=cefb9f88-0424-6701-5ba1-070490c69203 
CD 0 VBD:
uuid ( RO)             : 40f6b5c9-14fd-4379-d82c-d0ff34472a04
    vm-name-label ( RO): 955300270
            empty ( RO): false
       userdevice ( RW): 5


CD 0 VDI:
uuid ( RO)             : 0549c68a-e38d-4cd8-9974-ba0b9167ff5a
       name-label ( RW): CentOS-6.3-x86_64-LiveCD.iso
    sr-name-label ( RO): NFS ISO
     virtual-size ( RO): 725614592

6. Unplugging the CD disk

When done with the CD you can unplug it even easier. We specify the VM UUID and tell it to eject the CD which it does. 

 [ root@cloud2 ~/bin ] xe vm-cd-eject uuid=cefb9f88-0424-6701-5ba1-070490c69203

Xenserver hotfixes are released as patches that need to be applied with patch-pool-apply. Although technically this could work with XCP as long as you got the correct Xenserver patch it's better to apply patches the "new" way using Yum and the default xcp repository.

Any minor software updates to Xen Cloud Platform will be released into the XCP Yum repository at downloads.xen.org.  XCP 1.6 comes with a ready made Yum repository file at /etc/yum.repos.d/xcp.repo although by default the repository is disabled.

To apply updates use the yum update command you have to enable the repo and tell rpm not  to gpg check the packages. Hopefully the latter behavior will change in the future.

yum --enablerepo xcp --nogpgcheck update

If you'd like to enable the repo and turn gpg checking off by default so future updates are easier then change the enabled=0 line to enabled=1. Also add a line to the /etc/yum.repos.d/xcp.repo file to turn gpgchecking off for this ONE repository.

[xcp]
name=XCP 1.6 Updates
baseurl=http://downloads.xen.org/XCP/repo/xcp-1.6.10/
enabled=1
gpgcheck=0

I don't know if I recommend enabling by default as I like to do my updates manually. I really have issues with turning gpg checking off but currently the packages are distributed without a gpg signature so if you have it turned on the update will fail. Our only choice is to turn it off.

Note: Updated for XCP 1.5b/1.6

Install Type

• Non-interactive
• Network boot
• Commandline
• Paravirtualized

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.

Note: updated for XCP 1.5b/1.6

Install Type

• Non-interactive
• Network boot
• Commandline
• Paravirtualized

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.

Note: updated for XCP 1.5b/1.6

Install Type

• Non-interactive
• Network boot
• Commandline
• Paravirtualized

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.

Note: updated for XCP 1.5b/1.6

Install Type

• Non-interactive
• Network boot
• Commandline
• Paravirtualized

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.

Note: Updated to work with XCP 1.5b/1.6

Install Type

• Non-interactive
• Network boot
• Commandline
• Paravirtualized

Prerequisites

• XCP/Xenserver
• Access to Internet
• Working DHCP server
• Working DNS name resolution

Introduction

In this tutorial I create a disk, download a kernel, preseed file and install Ubuntu using the preseed 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 Ubuntu mirror locally then downloading my files and editing them.

Note: This is not quite functional. Ubuntu is asking a few questions during the install and then ultimately failing. I would recommend using my other Ubuntu 12.04 tutorial using a preseed file to auto install.

Note: Updated to work with XCP 1.5b/1.6

Thanks goes out to Alastair Brunton for troubleshooting this tutorial for me.

Install Type

• Non-interactive
• Network boot
• Commandline
• Paravirtualized

Prerequisites

• XCP/Xenserver
• Access to Internet
• Working DHCP server
• Working DNS name resolution

Introduction

This tutorial was written in the spirit of my CentOS 6 VM (64 bit) automated installation on XCP howto. In this tutorial I create a disk, download a kernel, kickstart file and install Ubuntu 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 Ubuntu mirror locally then downloading my files and editing them.

This tutorial isn't "debian pure" since I chose to use a kickstart file instead of a preseed file. I've created preseed files for doing automated installations of Ubuntu before but in this case I wanted this tutorial to be as close to the CentOS one as possible making it easier for me to maintain thus the kickstart file.