DSC

DSCForLinux Extension

Allow the owner of the Azure Virtual Machines to configure the VM using Desired State Configuration (DSC) for Linux.

Latest version is 2.71

About how to create MOF document, please refer to below documents.

• Get started with Desired State Configuration (DSC) for Linux
• Built-In Desired State Configuration Resources for Linux
• [DSC for Linux releases] (https://github.com/Microsoft/PowerShell-DSC-for-Linux/releases)

DSCForLinux Extension can:

• Register the Linux VM to Azure Automation account in order to pull configurations from Azure Automation service (Register ExtensionAction)
• Push MOF configurations to the Linux VM (Push ExtensionAction)
• Applies Meta MOF configuration to the Linux VM to configure Pull Server in order to pull Node Configuration (Pull ExtensionAction)
• Install custom DSC modules to the Linux VM (Install ExtensionAction)
• Remove custom DSC modules to the Linux VM (Remove ExtensionAction)

User Guide

1. Configuration schema

1.1. Public configuration

Here're all the supported public configuration parameters:

• FileUri: (optional, string) the uri of the MOF file/Meta MOF file/custom resource ZIP file.
• ResourceName: (optional, string) the name of the custom resource module
• ExtensionAction: (optional, string) Specifies what an extension does. valid values: Register, Push, Pull, Install, Remove. If not specified, it's considered as Push Action by default.
• NodeConfigurationName: (optional, string) the name of a node configuration to apply.
• RefreshFrequencyMins: (optional, int) Specifies how often (in minutes) DSC attempts to obtain the configuration from the pull server. If configuration on the pull server differs from the current one on the target node, it is copied to the pending store and applied.
• ConfigurationMode: (optional, string) Specifies how DSC should apply the configuration. Valid values are: ApplyOnly, ApplyAndMonitor, ApplyAndAutoCorrect.
• ConfigurationModeFrequencyMins: (optional, int) Specifies how often (in minutes) DSC ensures that the configuration is in the desired state.

NOTE: If you are using a version < 2.3, mode parameter is same as ExtensionAction. Mode seems to be a overloaded term. Therefore to avoid the confusion, ExtensionAction is being used from 2.3 version onwards. For backward compatibility, the extension supports both mode and ExtensionAction.

1.2 Protected configuration

Here're all the supported protected configuration parameters:

• StorageAccountName: (optional, string) the name of the storage account that contains the file
• StorageAccountKey: (optional, string) the key of the storage account that contains the file
• RegistrationUrl: (optional, string) the URL of the Azure Automation account
• RegistrationKey: (optional, string) the access key of the Azure Automation account

2. Deploying the Extension to a VM

You can deploy it using Azure CLI, Azure PowerShell and ARM template.

2.1. Using Azure CLI

Before deploying DSCForLinux Extension, you should configure your public.json and protected.json, according to the different scenarios in section 3.

2.1.1. Classic

The Classic mode is also called Azure Service Management mode. You can switch to it by running:

$ azure config mode asm

You can deploy DSCForLinux Extension by running:

$ azure vm extension set <vm-name> DSCForLinux Microsoft.OSTCExtensions <version> \
--private-config-path protected.json --public-config-path public.json

To learn the latest extension version available, run:

$ azure vm extension list

2.1.2. Resource Manager

You can switch to Azure Resource Manager mode by running:

$ azure config mode arm

You can deploy DSCForLinux Extension by running:

$ azure vm extension set <resource-group> <vm-name> \
DSCForLinux Microsoft.OSTCExtensions <version> \
--private-config-path protected.json --public-config-path public.json

NOTE: In ARM mode, azure vm extension list is not available for now.

2.2. Using Azure PowerShell

2.2.1 Classic

You can login to your Azure account (Azure Service Management mode) by running:

Add-AzureAccount

And deploy DSCForLinux Extension by running:

$vmname = '<vm-name>'
$vm = Get-AzureVM -ServiceName $vmname -Name $vmname

$extensionName = 'DSCForLinux'
$publisher = 'Microsoft.OSTCExtensions'
$version = '<version>'

# You need to change the content of the $privateConfig and $publicConfig 
# according to different scenarios in section 3
$privateConfig = '{
  "StorageAccountName": "<storage-account-name>",
  "StorageAccountKey": "<storage-account-key>"
}'

$publicConfig = '{
  "ExtensionAction": "Push",
  "FileUri": "<mof-file-uri>"
}'

Set-AzureVMExtension -ExtensionName $extensionName -VM $vm -Publisher $publisher `
  -Version $version -PrivateConfiguration $privateConfig `
  -PublicConfiguration $publicConfig | Update-AzureVM

2.2.2.Resource Manager

You can login to your Azure account (Azure Resource Manager mode) by running:

Login-AzureRmAccount

Click HERE to learn more about how to use Azure PowerShell with Azure Resource Manager.

You can deploy DSCForLinux Extension by running:

$rgName = '<resource-group-name>'
$vmName = '<vm-name>'
$location = '<location>'

$extensionName = 'DSCForLinux'
$publisher = 'Microsoft.OSTCExtensions'
$version = '<version>'

# You need to change the content of the $privateConfig and $publicConfig 
# according to different scenarios in section 3
$privateConfig = '{
  "StorageAccountName": "<storage-account-name>",
  "StorageAccountKey": "<storage-account-key>"
}'

$publicConfig = '{
  "ExtensionAction": "Push",
  "FileUri": "<mof-file-uri>"
}'

Set-AzureRmVMExtension -ResourceGroupName $rgName -VMName $vmName -Location $location `
  -Name $extensionName -Publisher $publisher -ExtensionType $extensionName `
  -TypeHandlerVersion $version -SettingString $publicConfig -ProtectedSettingString $privateConfig

2.3. Using ARM Template

The sample ARM template is 201-dsc-linux-azure-storage-on-ubuntu and 201-dsc-linux-public-storage-on-ubuntu.

For more details about ARM template, please visit Authoring Azure Resource Manager templates.

3. Scenarios

3.1 Register to Azure Automation account

protected.json

{
  "RegistrationUrl": "<azure-automation-account-url>",
  "RegistrationKey": "<azure-automation-account-key>"
}

public.json

{
  "ExtensionAction" : "Register",
  "NodeConfigurationName" : "<node-configuration-name>",
  "RefreshFrequencyMins" : "<value>",
  "ConfigurationMode" : "<ApplyAndMonitor | ApplyAndAutoCorrect | ApplyOnly>",
  "ConfigurationModeFrequencyMins" : "<value>"
}

powershell format

$privateConfig = '{
  "RegistrationUrl": "<azure-automation-account-url>",
  "RegistrationKey": "<azure-automation-account-key>"
}'

$publicConfig = '{
  "ExtensionAction" : "Register",
  "NodeConfigurationName": "<node-configuration-name>",
  "RefreshFrequencyMins": "<value>",
  "ConfigurationMode": "<ApplyAndMonitor | ApplyAndAutoCorrect | ApplyOnly>",
  "ConfigurationModeFrequencyMins": "<value>"
}'

3.2 Apply a MOF configuration file (in Azure Storage Account) to the VM

protected.json

{
  "StorageAccountName": "<storage-account-name>",
  "StorageAccountKey": "<storage-account-key>"
}

public.json

{
  "FileUri": "<mof-file-uri>",
  "ExtensionAction": "Push"
}

powershell format

$privateConfig = '{
  "StorageAccountName": "<storage-account-name>",
  "StorageAccountKey": "<storage-account-key>"
}'

$publicConfig = '{
  "FileUri": "<mof-file-uri>",
  "ExtensionAction": "Push"
}'

3.3. Apply a MOF configuration file (in public storage) to the VM

public.json

{
  "FileUri": "<mof-file-uri>"
}

powershell format

$publicConfig = '{
  "FileUri": "<mof-file-uri>"
}'

3.4. Apply a meta MOF configuration file (in Azure Storage Account) to the VM

protected.json

{
  "StorageAccountName": "<storage-account-name>",
  "StorageAccountKey": "<storage-account-key>"
}

public.json

{
  "ExtensionAction": "Pull",
  "FileUri": "<meta-mof-file-uri>"
}

powershell format

$privateConfig = '{
  "StorageAccountName": "<storage-account-name>",
  "StorageAccountKey": "<storage-account-key>"
}'

$publicConfig = '{
  "ExtensionAction": "Pull",
  "FileUri": "<meta-mof-file-uri>"
}'

3.5. Apply a meta MOF configuration file (in public storage) to the VM

public.json

{
  "FileUri": "<meta-mof-file-uri>",
  "ExtensionAction": "Pull"
}

powershell format

$publicConfig = '{
  "FileUri": "<meta-mof-file-uri>",
  "ExtensionAction": "Pull"
}'

3.6. Install a custom resource module (ZIP file in Azure Storage Account) to the VM

protected.json

{
  "StorageAccountName": "<storage-account-name>",
  "StorageAccountKey": "<storage-account-key>"
}

public.json

{
  "ExtensionAction": "Install",
  "FileUri": "<resource-zip-file-uri>"
}

powershell format

$privateConfig = '{
  "StorageAccountName": "<storage-account-name>",
  "StorageAccountKey": "<storage-account-key>"
}'

$publicConfig = '{
  "ExtensionAction": "Install",
  "FileUri": "<resource-zip-file-uri>"
}'

3.7. Install a custom resource module (ZIP file in public storage) to the VM

public.json

{
  "ExtensionAction": "Install",
  "FileUri": "<resource-zip-file-uri>"
}

powershell format

$publicConfig = '{
  "ExtensionAction": "Install",
  "FileUri": "<resource-zip-file-uri>"
}'

3.8. Remove a custom resource module from the VM

public.json

{
  "ResourceName": "<resource-name>",
  "ExtensionAction": "Remove"
}

powershell format

$publicConfig = '{
  "ResourceName": "<resource-name>",
  "ExtensionAction": "Remove"
}'

4. Supported Linux Distributions

• Ubuntu 14.04 LTS, 16.04 LTS, 18.04 LTS and 20.04 LTS
• Debian 8, 9 and 10
• Oracle Linux 6 and 7
• CentOS 6, 7 and 8
• RHEL 6, 7 and 8
• SUSE Linux Enterprise Server 12 and 15

5. Debug

• The status of the extension is reported back to Azure so that user can see the status on Azure Portal
• The operation log of the extension is /var/log/azure/<extension-name>/<version>/extension.log file.

6. Known issue

• To distribute MOF configurations to the Linux VM with Pull Servers, you need to make sure the cron service is running in the VM.

Changelog

# 2.5 (2017-05-25)
- Added support Oracle Distros
# 2.4 (2017-05-14)
- Added more logging
# 2.3 (2017-05-08)
- Update to OMI v1.1.0-8 and Linux DSC v1.1.1-294
- Added optional public.json parmeters: 'NodeConfigurationName', 'RefreshFrequencyMins', 'ConfigurationMode' and 'ConfigurationModeFrequencyMins'.
- Added a new parameter 'ExtensionAction' to replace 'mode' to avoid confusion with DSC terminology: push/pull mode.
- Supports mode parameter for backward compatibility.

# 2.0 (2016-03-10)
- Pick up Linux DSC v1.1.1
- Add function to register Azure Automation
- Refine extension configurations

# 1.0 (2015-09-24)
- Initial version