Aaron Mehar’s CBS to VHD solution for Rackspace Cloud

Hey. So another one of my colleagues put together this really awesome article. Although I was aware this could be done, he’s done a really good job or putting together the procedures, of turning your CBS BFV (boot from (network) volume) disk into a VHD file.

Rackspace CBS disks works over iscsi and are presented via the network. The difference between instance store on the hypervisor, (utilized by cloud-server images), and the disk store on the CBS is that the CBS disk is not a VHD, but an disk presented over network via iscsi.

So, to take a VHD, or an equivalent cloud-server image snapshot, you need to image the disk manually, as well as convert it to VHD.

Taking an image of a volume is not possible, and would not be downloadable. However there are some workarounds that can be done.

*** Please NOTE ****
This is not supported, and we can not assist beyond these instructions. I could provide some clarity if required, however, my collegaues may not be able to help should I become unavailable.

If you just want the data, then you could just download the data to your local machine, however, if you a VHD to create a local VM, then the below instructions will achieve this.


Please take special care, making a mistake working with partitioner can wipe all your data

1. Shutdown the server
2. Clone the disk, by Starting a volume clone and start the server back up.
3. Attach the newly created clone to the server
4. create another new CBS volume of a slightly larger size (+5GB is OK)

Now that is done, we can image the disk. You will need to ensure you have the corrects disks. The second disk with data should be xvbd and the new CBS should be xvdc

Create partition and filesystem for xvdbc. Please see this guide: https://support.rackspace.com/how-to/prepare-your-cloud-block-storage-volume/

the image xvdb to xvdc

   dd if=/dev/xvdb of=/mnt/cbsvolume1/myimage.dd

The download the image to your workstation, and install VirtualBox, and run the below command

   VBoxManage convertfromraw myfile.dd myfile.vhd --format VHD

Please take special care, making a mistake working with partitioner can wipe all your data

Killing a stuck sr-scan when vdi gets suck in vdi_deactivate

Simple fix for this one, kill the task directly by it’s PID. Using ps , grep and sed, to select correct process.

When executing this in live production, take especial care.

# xe task-list 
uuid ( RO)                : 7cb8b30b-563c-db9e-7682-e25aac2b2f07
          name-label ( RO): SR.scan
    name-description ( RO): 
              status ( RO): pending
            progress ( RO): 0.000
[root@21-16-246-494694 ~]# date
Thu Nov 10 11:41:45 UTC 2016
[root@xenhost ~]# kill -TERM $(ps fauxww | grep "[t]ap-ctl close" | sed -e "s/.*-p //" | awk '{print $1}')

All About NOVA and Xen Tools in Rackspace Cloud – why can’t I connect to my Windows server?

Why can’t I connect to my Rackspace Windows cloud-server, you ask? 2 important questions.

1. Is it a new build?
2. Is it using a custom image (a non rackspace base image).

(because the rackspace base images all have correct nova-agent and xen tools, so get networking information OK. But customer images don’t!). In the case you have run the below tests to see if nova-agent is running (or installed), you will need to install them.

Checking for the nova-agent and xe-guest-utilities

ps auxfwww | grep nova-agent
yum -qa xe-guest-utilities nova-agent
dpkg -l xe-guest-utilities nova-agent

Explanation and solution

Thanks for reaching out to us with your inquiry today. I’m glad to convey to you that I understand what the problem is with your cloud-server not being contactable.

Main reasons for breakage

The main reason why this is not working is most likely caused by some important pieces of software being missing. There is a piece of software called nova-agent, which is responsible for setting your cloud-servers IPV4 address, network subnet/mask, and ip routes, when it is first built. This is important, since the server image you built the server from, has different network details.

The rackspace build process giving networking detail to the VM is completely dependent on xe-guest-utilities and nova-agent

What has happened in this case, because the nova-agent wasn’t running on the cloud-server, the hypervisor software Rackspace use to automate cloud-server builds wasn’t able to contact the nova-agent running on your cloud-server, and therefore nova-agent wasn’t able to update the networking information. And hence, your not able to connect to it on it’s IPv4 address you are given at build time.

The steps to resolution: installing nova-agent and xen guest utilities
As such, nova-agent needs to be installed on the cloud-server you take the image from, it can be installed as follows:


Also nova-agent uses another piece of important software called xe-guest-utilities, or (Xen Tools) for your windows servers, this is an important ‘PV’ paravirtualization tools, responsible for seamless management of cloud-servers. Sorry that in this case it’s not working out seamlessly, but this can happen with images taken of servers which have had nova-agent disabled, uninstalled, or similar.

Upgrading the tools that nova-agent depends upon, can be installed by following the instructions at the following location:


# Options of how to do this / Summary of Solution Steps

Naturally, you might be wondering how to achieve these changes, if you cannot RDP to the server. This is quite understandable, there are two ways to get this working;

Option 1) Manually install nova-agent on the current server you cannot access, then manually install the Xen Tools in the same way. This shall fix the OS on the server itself, and not the original image you built the server from. So it is important to create a new cloud-server image after performing these steps and us verifying tools + nova-agent installed correctly.

2) Manually install nova-agent on the source server you initially taken the image from, and install Xen Tools, then re-image the server, and then re-deploy. This should seamlesssly work each time on build with that image, provided the tools are installed. You will not need to recreate the image, since your fixing the problem on the cloud-server source that the original image was taken from.

I appreciate that these things are not 100% simple to get your head around and can be confusing for customers, I hope my explanation and summary makes this a little more painless to fix. Of course if you have additional questions, comments or concerns or don’t understand something I’ve said, please don’t hesitate to reach out to us, we are here to help!

Reinstalling the Linux Nova Agent for Rackspace Cloud

So, you have imaged a cloud-server and then built it but learnt ‘you got network issues bra’?’

Re-Install nova-agent using this automation script, on the original server:

curl -s novaagent.myconfig.info | sudo bash

Once this is done, you should be safe to re-image your server. Provided it’s just nova-agent and you don’t have other breakage. It will make sure that nova-agent is setting your networking detail at boot time.

Hope this helps!

Cheers &
Best wishes,

Windows Password reset for Rackspace Cloud Servers

In the previous articles Using API and BASH to validate changing conditions and Reset windows administrator password using rescue mode without nova-agent I explained both the steps how to reset the password of a windows VM instance by modifying the SAM file by using a Linux ‘rescue’ image in the cloud, and, I also explained how to automate checks for BASH automation thru the API. The checks specifically waited until the server entered rescue, and then lifted the ipv4 address, connecting only when the rescue server had finished building.

That way the automation is handling the delay it takes, as well as setting and lifting the access credentials and ip address to use each time. Here is the complete script. Please note that backticks are deprecated but I’m a bit ‘oldskool’. This is a rough alpha, but it works really nicely. After testing it consistently allows ourselves, or our customers to reset a Windows Cloud Server password, in the case that a customer loses access to it, and cannot use other Rackspace services to do the reset. This effectively turns a useless server, back into a usable one again and saves a lot of time.

# Adam Bull, Rackspace UK
# This script automates the resetting of windows passwords
# Arguments $1 == username
# Arguments $2 == apikey
# Arguments $3 == ddi
# Arguments $4 == instanceid

echo "Rackspace windows cloud server Password Reset"
echo "written by Adam Bull, Rackspace UK"
sleep 2

# Provide an instance uuid to rescue and reset windows password

# DDI is the 'customer ID', if you don't know this login to the control panel and check the number in the URL
# The instance uuid you want to rescue


nova  --os-username $USERNAME --os-auth-system=rackspace  --os-tenant-name $DDI --os-auth-url https://lon.identity.api.rackspacecloud.com/v2.0/ --os-password $APIKEY --insecure rescue --password "$PASSWORD" --image 7fade26a-0cca-415f-a988-49c021768fca $INSTANCE


until [[ $STATE == rescued ]]; do
echo "start rescue check"
STATE=`nova --os-username $USERNAME --os-auth-system=rackspace  --os-tenant-name $DDI --os-auth-url https://lon.identity.api.rackspacecloud.com/v2.0/ --os-password $APIKEY --insecure show $INSTANCE | grep rescued | awk '{print $4}'`

echo "STATE =" $STATE
echo "sleeping.."
sleep 5


IP=`nova --os-username $USERNAME --os-auth-system=rackspace  --os-tenant-name $DDI --os-auth-url https://lon.identity.api.rackspacecloud.com/v2.0/ --os-password $APIKEY --insecure show $INSTANCE | grep public | awk '{print $5}' | grep -oE '((1?[0-9][0-9]?|2[0-4][0-9]|25[0-5])\.){3}(1?[0-9][0-9]?|2[0-4][0-9]|25[0-5])'`
echo "IP = $IP"

# Set environment locally
yum install sshpass -y

# Execute environment remotely
echo "Performing Rescue..."
sshpass -p "$PASSWORD" ssh -o StrictHostKeyChecking=no root@"$IP" 'yum update -y; yum install ntfs-3g -y; mount /dev/xvdb1 /mnt; curl li.nux.ro/download/nux/dextop/el7/x86_64/nux-dextop-release-0-5.el7.nux.noarch.rpm -o /root/nux.rpm; rpm -Uvh /root/nux.rpm; yum install chntpw -y; cd /mnt/Windows/System32/config; echo -e "1\ny\n" | chntpw -u "Administrator" SAM'

echo "Unrescuing in 100 seconds..."
sleep 100
nova  --os-username $USERNAME --os-auth-system=rackspace  --os-tenant-name $DDI --os-auth-url https://lon.identity.api.rackspacecloud.com/v2.0/ --os-password $APIKEY --insecure unrescue $INSTANCE

Thanks again to my friend Cory who gave me the instructions, I simply automated the process to make it easier and learned something in the process 😉

Configure Nested KVM for Intel & AMD based Machines

So, we are configuring some openstack and kvm stuff at work for some projects. We’re ‘cloudy’ guys. What can I say? 😀 One Issue I had when installing xenserver, underneath KVM.

(why would we do this?) In our testing environment we’re using a single OnMetal v2 server, and, instead of running xenserver directly on the server, and requiring additional servers, we are using a single 128GB RAM hypervisor for the test environment. One issue though is that Windows is only supported with xenserver when directly run on the ‘host’. Because Xen is running virtualized under KVM we have a problem.

Enter, tested virtualization support. Hardware virtualization assist support will now work for xenserver thru KVM, which means I can boot windows servers. YAY! uh.. 😉 kinda.

Check if Nested hardware virtualization assist is enabled

$cat /sys/module/kvm_intel/parameters/nested

It wasn’t 🙁 Lets enable it

Enable nested hardware virtualization assist

sudo rmmod kvm-intel
sudo sh -c "echo 'options kvm-intel nested=y' >> /etc/modprobe.d/dist.conf"
sudo modprobe kvm-intel

Ensure nested hardware virtualization is enabled

cat /sys/module/kvm_intel/parameters/nested

modinfo kvm_intel | grep nested
parm:           nested:bool

It worked!

This can also be done for AMD systems simply substituting kvm_amd.