Creating a Windows image for OpenStack
If you want to build a Windows image for use in your OpenStack environment, you can follow the example in the official documentation, or you can grab a Windows 2012r2 evaluation pre-built image from the nice folks at CloudBase.
The CloudBase-provided image is built using a set of scripts and configuration files that CloudBase has made available on GitHub.
The CloudBase repository is an excellent source of information, but I wanted to understand the process myself. This post describes the process I went through to establish an automated process for generating a Windows image suitable for use with OpenStack.
Unattended windows installs⌗
The Windows installer supports fully automated installations through
the use of an answer file, or “unattend” file, that provides
information to the installer that would otherwise be provided
manually. The installer will look in a number of places to find
this file. For our purposes, the important fact is that the installer
will look for a file named autounattend.xml
in the root of all
available read/write or read-only media. We’ll take advantage of this
by creating a file config/autounattend.xml
, and then generating an
ISO image like this:
mkisofs -J -r -o config.iso config
And we’ll attach this ISO to a vm later on in order to provide the answer file to the installer.
So, what goes into this answer file?
The answer file is an XML document enclosed in an
<unattend>..</unattend>
element. In order to provide all the
expected XML namespaces that may be used in the document, you would
typically start with something like this:
<?xml version="1.0" ?>
<unattend
xmlns="urn:schemas-microsoft-com:unattend"
xmlns:ms="urn:schemas-microsoft-com:asm.v3"
xmlns:wcm="http://schemas.microsoft.com/WMIConfig/2002/State">
<!-- your content goes here -->
</unattend>
Inside this <unattend>
element you will put one or more <settings>
elements, corresponding to the different configuration passes of the
installer:
<settings pass="specialize">
</settings>
The available configuration passes are:
Of these, the most interesting for our use will be:
windowsPE
– used to install device drivers for use within the installer environment. We will use this to install the VirtIO drivers necessary to make VirtIO devices visible to the Windows installer.specialize
– In this pass, the installer applies machine-specific configuration. This is typically used to configure networking, locale settings, and most other things.oobeSystem
– In this pass, the installer configures things that happen at first boot. We use this to step to install some additional software and run sysprep in order to prepare the image for use in OpenStack.
Inside each <settings>
element we will place one or more
<component>
elements that will apply specific pieces of
configuration. For example, the following <component>
configures
language and keyboard settings in the installer:
<settings pass="windowsPE">
<component name="Microsoft-Windows-International-Core-WinPE"
processorArchitecture="amd64"
publicKeyToken="31bf3856ad364e35"
language="neutral"
versionScope="nonSxS">
<SetupUILanguage>
<UILanguage>en-US</UILanguage>
</SetupUILanguage>
<InputLocale>en-US</InputLocale>
<UILanguage>en-US</UILanguage>
<SystemLocale>en-US</SystemLocale>
<UserLocale>en-US</UserLocale>
</component>
</settings>
Technet provides documentation on the available components.
Cloud-init for Windows⌗
Cloud-init is a tool that will configure a virtual instance when
it first boots, using metadata provided by the cloud service provider.
For example, when booting a Linux instance under OpenStack,
cloud-init
will contact the OpenStack metadata service at
http://169.254.169.254/ in order to retrieve things like the system
hostname, SSH keys, and so forth.
While cloud-init
has support for Linux and BSD, it does not support
Windows. The folks at Cloudbase have produced cloudbase-init
in order to fill this gap. Once installed, the cloudbase-init
tool
will, upon first booting a system:
- Configure the network using information provided in the cloud metadata
- Set the system hostname
- Create an initial user account (by default “Admin”) with a randomly generated password (see below for details)
- Install your public key, if provided
- Execute a script provided via cloud
user-data
Passwords and ssh keys⌗
While cloudbase-init
will install your SSH public key (by default
into /Users/admin/.ssh/authorized_keys
), Windows does not ship with
an SSH server and cloudbase-init does not install one. So what is it
doing with the public key?
While you could arrange to install an ssh server that would make use
of the key, cloudbase-init
uses it for a completely unrelated
purpose: encrypting the randomly generated password. This encrypted
password is then passed back to OpenStack, where you can retrieve it
using the nova get-password
command, and decrypt it using the
corresponding SSH private key.
Running nova get-password myinstance
will return something like: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Providing your secret key as an additional parameter will decrypt the password:
$ nova get-password myinstance ~/.ssh/id_rsa
fjgJmUB7fXF6wo
With an appropriately configured image, you could connect using an RDP client and log in as the “Admin” user using that password.
Passwords without ssh keys⌗
If you do not provide your instance with an SSH key you will not be able to retrieve the randomly generated password. However, if you can get console access to your instance (e.g., via the Horizon dashboard), you can log in as the “Administrator” user, at which point you will be prompted to set an initial password for that account.
Logging⌗
You can find logs for cloudbase-init
in c:\program files (x86)\cloudbase solutions\cloudbase-init\log\cloudbase-init.log
.
If appropriately configured, cloudbase-init
will also log to the
virtual serial port. This log is available in OpenStack by running
nova console-log <instance>
. For example:
$ nova console-log my-windows-server
2014-11-19 04:10:45.887 1272 INFO cloudbaseinit.init [-] Metadata service loaded: 'HttpService'
2014-11-19 04:10:46.339 1272 INFO cloudbaseinit.init [-] Executing plugin 'MTUPlugin'
2014-11-19 04:10:46.371 1272 INFO cloudbaseinit.init [-] Executing plugin 'NTPClientPlugin'
2014-11-19 04:10:46.387 1272 INFO cloudbaseinit.init [-] Executing plugin 'SetHostNamePlugin'
.
.
.
Putting it all together⌗
I have an install script that drives the process, but it’s
ultimately just a wrapper for virt-install
and results in the
following invocation:
exec virt-install -n ws2012 -r 2048 \
-w network=default,model=virtio \
--disk path=$TARGET_IMAGE,bus=virtio \
--cdrom $WINDOWS_IMAGE \
--disk path=$VIRTIO_IMAGE,device=cdrom \
--disk path=$CONFIG_IMAGE,device=cdrom \
--os-type windows \
--os-variant win2k8 \
--vnc \
--console pty
Where TARGET_IMAGE
is the name of a pre-existing qcow2
image onto
which we will install Windows, WINDOWS_IMAGE
is the path to an ISO
containing Windows Server 2012r2, VIRTIO_IMAGE
is the path to an ISO
containing VirtIO drivers for Windows (available from the Fedora
project), and CONFIG_IMAGE
is a path to the ISO containing our
autounattend.xml
file.
The fully commented autounattend.xml file, along with the script mentioned above, are available in my windows-openstack-image repository on GitHub.
The answer file in detail⌗
windowsPE⌗
In the windowsPE phase, we start by configuring the installer locale settings:
<component name="Microsoft-Windows-International-Core-WinPE"
processorArchitecture="amd64"
publicKeyToken="31bf3856ad364e35"
language="neutral"
versionScope="nonSxS">
<SetupUILanguage>
<UILanguage>en-US</UILanguage>
</SetupUILanguage>
<InputLocale>en-US</InputLocale>
<UILanguage>en-US</UILanguage>
<SystemLocale>en-US</SystemLocale>
<UserLocale>en-US</UserLocale>
</component>
And installing the VirtIO drviers using the Microsoft-Windows-PnpCustomizationsWinPE component:
<component name="Microsoft-Windows-PnpCustomizationsWinPE"
publicKeyToken="31bf3856ad364e35" language="neutral"
versionScope="nonSxS" processorArchitecture="amd64">
<DriverPaths>
<PathAndCredentials wcm:action="add" wcm:keyValue="1">
<Path>d:\win8\amd64</Path>
</PathAndCredentials>
</DriverPaths>
</component>
This assumes that the VirtIO image is mounted as drive d:
.
With the drivers installed, we can then call the Microsoft-Windows-Setup component to configure the disks and install Windows. We start by configuring the product key:
<component name="Microsoft-Windows-Setup"
publicKeyToken="31bf3856ad364e35"
language="neutral"
versionScope="nonSxS"
processorArchitecture="amd64">
<UserData>
<AcceptEula>true</AcceptEula>
<ProductKey>
<WillShowUI>OnError</WillShowUI>
<Key>INSERT-PRODUCT-KEY-HERE</Key>
</ProductKey>
</UserData>
And then configure the disk with a single partition (that will grow to fill all the available space) which we then format with NTFS:
<DiskConfiguration>
<WillShowUI>OnError</WillShowUI>
<Disk wcm:action="add">
<DiskID>0</DiskID>
<WillWipeDisk>true</WillWipeDisk>
<CreatePartitions>
<CreatePartition wcm:action="add">
<Order>1</Order>
<Extend>true</Extend>
<Type>Primary</Type>
</CreatePartition>
</CreatePartitions>
<ModifyPartitions>
<ModifyPartition wcm:action="add">
<Format>NTFS</Format>
<Order>1</Order>
<PartitionID>1</PartitionID>
<Label>System</Label>
</ModifyPartition>
</ModifyPartitions>
</Disk>
</DiskConfiguration>
We provide information about what to install:
<ImageInstall>
<OSImage>
<WillShowUI>Never</WillShowUI>
<InstallFrom>
<MetaData>
<Key>/IMAGE/Name</Key>
<Value>Windows Server 2012 R2 SERVERSTANDARDCORE</Value>
</MetaData>
</InstallFrom>
And where we would like it installed:
<InstallTo>
<DiskID>0</DiskID>
<PartitionID>1</PartitionID>
</InstallTo>
</OSImage>
</ImageInstall>
specialize⌗
In the specialize phase, we start by setting the system name to a randomly generated value using the Microsoft-Windows-Shell-Setup component:
<component name="Microsoft-Windows-Shell-Setup"
publicKeyToken="31bf3856ad364e35" language="neutral"
versionScope="nonSxS" processorArchitecture="amd64">
<ComputerName>*</ComputerName>
</component>
We enable remote desktop because in an OpenStack environment this will probably be the preferred mechanism with which to connect to the host (but see this document for an alternative mechanism).
First, we need to permit terminal server connections:
<component name="Microsoft-Windows-TerminalServices-LocalSessionManager"
processorArchitecture="amd64"
publicKeyToken="31bf3856ad364e35"
language="neutral"
versionScope="nonSxS">
<fDenyTSConnections>false</fDenyTSConnections>
</component>
And we do not want to require network-level authentication prior to connecting:
<component name="Microsoft-Windows-TerminalServices-RDP-WinStationExtensions"
processorArchitecture="amd64"
publicKeyToken="31bf3856ad364e35"
language="neutral"
versionScope="nonSxS">
<UserAuthentication>0</UserAuthentication>
</component>
We will also need to open the necessary firewall group:
<component name="Networking-MPSSVC-Svc"
processorArchitecture="amd64"
publicKeyToken="31bf3856ad364e35"
language="neutral"
versionScope="nonSxS">
<FirewallGroups>
<FirewallGroup wcm:action="add" wcm:keyValue="RemoteDesktop">
<Active>true</Active>
<Profile>all</Profile>
<Group>@FirewallAPI.dll,-28752</Group>
</FirewallGroup>
</FirewallGroups>
</component>
Finally, we use the Microsoft-Windows-Deployment component to configure the Windows firewall to permit ICMP traffic:
<component name="Microsoft-Windows-Deployment"
processorArchitecture="amd64"
publicKeyToken="31bf3856ad364e35"
language="neutral" versionScope="nonSxS">
<RunSynchronous>
<RunSynchronousCommand wcm:action="add">
<Order>3</Order>
<Path>netsh advfirewall firewall add rule name=ICMP protocol=icmpv4 dir=in action=allow</Path>
</RunSynchronousCommand>
And to download the cloudbase-init
installer and make it available
for later steps:
<RunSynchronousCommand wcm:action="add">
<Order>5</Order>
<Path>powershell -NoLogo -Command "(new-object System.Net.WebClient).DownloadFile('https://www.cloudbase.it/downloads/CloudbaseInitSetup_Beta_x64.msi', 'c:\Windows\Temp\cloudbase.msi')"</Path>
</RunSynchronousCommand>
</RunSynchronous>
</component>
We’re using Powershell here because it has convenient methods
available for downloading URLs to local files. This is roughly
equivalent to using curl
on a Linux system.
oobeSystem⌗
In the oobeSystem phase, we configure an automatic login for the Administrator user:
<UserAccounts>
<AdministratorPassword>
<Value>Passw0rd</Value>
<PlainText>true</PlainText>
</AdministratorPassword>
</UserAccounts>
<AutoLogon>
<Password>
<Value>Passw0rd</Value>
<PlainText>true</PlainText>
</Password>
<Enabled>true</Enabled>
<LogonCount>50</LogonCount>
<Username>Administrator</Username>
</AutoLogon>
This automatic login only happens once, because we configure
FirstLogonCommands
that will first install cloudbase-init
:
<FirstLogonCommands>
<SynchronousCommand wcm:action="add">
<CommandLine>msiexec /i c:\windows\temp\cloudbase.msi /qb /l*v c:\windows\temp\cloudbase.log LOGGINGSERIALPORTNAME=COM1</CommandLine>
<Order>1</Order>
</SynchronousCommand>
And will then run sysprep
to generalize the system (which will,
among other things, lose the administrator password):
<SynchronousCommand wcm:action="add">
<CommandLine>c:\windows\system32\sysprep\sysprep /generalize /oobe /shutdown</CommandLine>
<Order>2</Order>
</SynchronousCommand>
</FirstLogonCommands>
The system will shut down when sysprep
is complete, leaving you with a
Windows image suitable for uploading into OpenStack:
glance image-create --name ws2012 \
--disk-format qcow2 \
--container-format bare \
--file ws2012.qcow2
Troubleshooting⌗
If you run into problems with an unattended Windows installation:
During the first stage of the installer, you can look in the
x:\windows\panther
directory for setupact.log
and setuperr.log
,
which will have information about the early install process. The x:
drive is temporary, and files here will be discarded when the system
reboots.
Subsequent installer stages will log to
c:\windows\panther\
.
If you are unfamiliar with Windows, the type
command can be used
very much like the cat
command on Linux, and the more
command
provides paging as you would expect. The notepad
command will open
a GUI text editor/viewer.
You can emulate the tail
command using powershell
; to see the last
10 lines of a file:
C:\> powershell -command "Get-Content setupact.log -Tail 10"
Technet has a Deployment Troubleshooting and Log Files document that discusses in more detail what is logged and where to find it.