runner-images/docs/create-image-and-azure-resources.md

# GitHub Actions Runner Images

The runner-images project uses [Packer](https://www.packer.io/) to generate disk images for Windows 2019/2022 and Ubuntu 20.04/22.04.

Each image is configured by a JSON or HCL2 Packer template that specifies where to build the image (Azure in this case)
and what steps to run to install software and prepare the disk.

The Packer process initializes a connection to Azure subscription using Azure CLI and creates temporary resources
required for the build process: resource group, network interfaces and virtual machine from the "clean" image specified in the template.

If the VM deployment succeeds, Packer connects it using ssh or WinRM and begins executing installation steps from the template one-by-one.
If any step fails, image generation is aborted and the temporary VM is terminated.
Packer also attempts to cleanup all the temporary resources it created (unless otherwise configured).

After successful completion of all installation steps Packer converts snapshot of the temporary VM to VHD image
and uploads it to the specified Azure Storage Account.

## Build agent preparation

Build agent is a machine where Packer process will be started.
You can use any physical or virtual machine running OS Windows or Linux.
Of course you may also use [Azure VM](https://docs.microsoft.com/en-us/azure/virtual-machines/windows/quick-create-cli).
In any case you will need these software installed:

- Packer 1.8.2 or higher.

  Download and install it manually from [here](https://www.packer.io/downloads) or use [Chocolatey](https://chocolatey.org/):

  ```powershell
  choco install packer
  ```

- Git.

  For Linux - install the latest version from your distro's package repo.

  For Windows - download and install it from [here](https://gitforwindows.org/) of use [Chocolatey](https://chocolatey.org/):

  ```powershell
  choco install git -params '"/GitAndUnixToolsOnPath"'
  ```

- Powershell 5.0 or higher.

  In Windows you already have it.

  For Linux follow instructions [here](https://learn.microsoft.com/en-us/windows-server/administration/linux-package-repository-for-microsoft-software)
  to add Microsoft's Linux Software Repository and then install package `powershell`.
- Azure CLI.

  Follow instructions [here](https://docs.microsoft.com/en-us/cli/azure/install-azure-cli).
  Or if you use Windows you may run this command in Powershell instead:

  ```powershell
  Invoke-WebRequest -Uri https://aka.ms/installazurecliwindows -OutFile .\AzureCLI.msi
  Start-Process msiexec.exe -Wait -ArgumentList '/I AzureCLI.msi /quiet'; rm .\AzureCLI.msi
  ```

- [Az Powershell module](https://docs.microsoft.com/en-us/powershell/azure/install-az-ps).

  Run this command in Powershell:

  ```powershell
  Install-Module -Name Az -Repository PSGallery -Force
  ```

## Automated image generation

This repo bundles script that automates image generation process.
You only need a build agent configured as described above and active Azure subsctiption.
We suggest to start with UbuntuMinimal image because it includes only a minimal set of required software and builds in less then half an hour.

All steps here are supposed to run in Powershell.

First, clone runner-images repository and change directory:

```powershell
git clone https://github.com/actions/runner-images.git
Set-Location runner-images
```

Then import [GenerateResourcesAndImage](../helpers/GenerateResourcesAndImage.ps1) script from `helpers` subdirectory:

```powershell
Import-Module .\helpers\GenerateResourcesAndImage.ps1
```

> :warning: When running `GenerateResourcesAndImage` in PowerShell 7.3, following command should be executed first:
> ```powershell
> $PSNativeCommandArgumentPassing = 'Legacy'
> ```

Finally, run `GenerateResourcesAndImage` function setting mandatory arguments: image type and where to create resources:

- `SubscriptionId` - your Azure Subscription ID
- `ResourceGroupName` - name of the resource group that will be created within your subscription (e.g. "imagegen-test")
- `AzureLocation` - location where resources will be created (e.g. "East US")
- `ImageType` - what image to build (we suggest choosing "UbuntuMinimal" here, other valid options are "Windows2019", "Windows2022", "Ubuntu2004", "Ubuntu2204")

This function automatically creates all required Azure resources and kicks off packer image generation for the selected image type.

When image is ready you may proceed to [deployment](#generated-machine-deployment)

## Image generation customization

Function `GenerateResourcesAndImage` accepts a bunch of arguments that may help you generating image in your specific environment.

For example, you may want that all the resources involved in image generation process are tagged.
In this case pass a HashTable of tags as a value for `Tags` parameter.

If you don't want function to authenticate interactively, you should create Service Principal and invoke the function with parameters `AzureClientId`, `AzureClientSecret` and `AzureTenantId`.
You can find more details [in corresponding section below](#azure-subscription-authentication).

Use `get-help GenerateResourcesAndImage -Detailed` for the complete list of parameters available.

### Network security

To connect to a temporary virtual machine Packer uses WinRM or SSH.

If your build agent is located outside of the Azure subscription where temporary VM is created, the public network interface and public IP address is used.
Make sure that firewalls are configured properly and WinRM (tcp port 5986) and ssh (tcp port 22) connections are allowed both outgoing for build agent and incoming for temporary VM.
Also if you don't want temporary VM to be accessible from everywhere, set `RestrictToAgentIpAddress` parameter value to `$true`
to setup firewall rules allowing access only from your build agent public IP address.

If your build agent and temporary VM are in the same subscription you can configure Packer to connect using private virtual network.
To achieve that set proper values for environment variables `VNET_RESOURCE_GROUP`, `VNET_NAME` and `VNET_SUBNET`.

### Azure subscription authentication

Packer uses Service Principal to authenticate in Azure infrastructure.
For more information about Service Principals refer to
[Azure documentation](https://docs.microsoft.com/en-us/azure/active-directory/develop/howto-create-service-principal-portal).

Function `GenerateResourcesAndImage` is able to create Service Principle to be used by Packer.
It uses Connect-AzAccount cmdlet that invokes interactive authentication process by default.
If you don't want to use interactive authentication you should create Service Principal with full read-write permissions for selected Azure subscription on your own
and provide proper values for parameters `AzureClientId`, `AzureClientSecret` and `AzureTenantId`.

Here is an example of how to create Service Principle using Az Powershell module:

```powershell
$credentials = [Microsoft.Azure.PowerShell.Cmdlets.Resources.MSGraph.Models.ApiV10.MicrosoftGraphPasswordCredential]@{
  StartDateTime = Get-Date
  EndDateTime = (Get-Date).AddDays(7)
}

$sp = New-AzADServicePrincipal -DisplayName "imagegen-app"
$appCred = New-AzADAppCredential -ApplicationId $sp.AppId -PasswordCredentials $credentials

Start-Sleep -Seconds 30
New-AzRoleAssignment -RoleDefinitionName "Contributor" -PrincipalId $sp.Id
Start-Sleep -Seconds 30

@{
  ClientId = $sp.AppId
  ClientSecret = $appCred.SecretText
  TenantId = (Get-AzSubscription -SubscriptionId $SubscriptionId).TenantId
}
```

## Generated machine deployment

After the successful image generation, Virtual Machine can be created from the generated VHD using [CreateAzureVMFromPackerTemplate](../helpers/CreateAzureVMFromPackerTemplate.ps1) script.

```powershell
Import-Module .\helpers\CreateAzureVMFromPackerTemplate.ps1

CreateAzureVMFromPackerTemplate -SubscriptionId {YourSubscriptionId}  -ResourceGroupName {ResourceGroupName} -TemplateFile "C:\BuildVmImages\temporaryTemplate.json" -VirtualMachineName "testvm1" -AdminUsername "shady1" -AdminPassword "SomeSecurePassword1" -AzureLocation "eastus"
```

Where:

- `SubscriptionId` - The Azure subscription Id where resources will be created.
- `ResourceGroupName` - The Azure resource group name where the Azure virtual machine will be created.
- `TemplateFilePath` - The path to the json ARM-template generated by packer during image generation locally.*
- `VirtualMachineName` - The name of the virtual machine to be generated.
- `AdminUserName` - The administrator username for the virtual machine to be created.
- `AdminPassword` - The administrator password for the virtual machine to be created.
- `AzureLocation` - The location where the Azure virtual machine will be provisioned. Example: "eastus"

\* *ARM-template can be obtained from the Packer output. For now, it seems like there is an [Az CLI bug](https://github.com/Azure/azure-cli/issues/5899) with specifying the template through a URI, so download the template from URI, that will be printed at the bottom of image-generation log, and use the local path of the template file.*

The function creates an Azure VM from a template and generates network resources in Azure to make the VM accessible.

## Manual image generation

If you want more control over image generation process you may run Packer directly. This section describes variables defined in Packer template. Some of them may be set using environment variabes.

### Required variables

| Template var | Env var | Description
| ------------ | ------- | -----------
| `subscription_id` | `ARM_SUBSCRIPTION_ID` | Subscription under which the build will be performed.
| `client_id` | `ARM_CLIENT_ID` | The Active Directory service principal associated with your builder.
| `client_secret` | `ARM_CLIENT_SECRET` | The password or secret for your service principal; may be omitted if `client_cert_path` is set.
| `client_cert_path` | `ARM_CLIENT_CERT_PATH` | The location of a PEM file containing a certificate and private key for service principal; may be omitted if `client_secret` is set.
| `location` | `ARM_RESOURCE_LOCATION` | Azure datacenter in which your VM will build.
| `resource_group` | `ARM_RESOURCE_GROUP` | Resource group under which the final artifact will be stored.
| `storage_account` | `ARM_STORAGE_ACCOUNT` | Storage account under which the final artifact will be stored.

### Optional variables

- `build_resource_group_name` - Specify an existing resource group to run the build in it. By default, a temporary resource group will be created and destroyed as part of the build. If you do not have permission to do so, use build_resource_group_name to specify an existing resource group to run the build in it.
- `object_id` - The object ID for the AAD SP. Will be derived from the oAuth token if empty.
- `tenant_id` - The Active Directory tenant identifier with which your `client_id` and `subscription_id` are associated. If not specified, `tenant_id` will be looked up using `subscription_id`.
- `temp_resource_group_name` - Name assigned to the temporary resource group created during the build. If this value is not set, a random value will be assigned. This resource group is deleted at the end of the build.
- `private_virtual_network_with_public_ip` - This value allows you to set a `virtual_network_name` and obtain a public IP. If this value is not set and `virtual_network_name` is defined Packer is only allowed to be executed from a host on the same subnet / virtual network.
- `virtual_network_name` - Use a pre-existing virtual network for the VM. This option enables private communication with the VM, no public IP address is used or provisioned (unless you set `private_virtual_network_with_public_ip`).
- `virtual_network_resource_group_name` - If `virtual_network_name` is set, this value may also be set. If `virtual_network_name` is set, and this value is not set the builder attempts to determine the resource group containing the virtual network. If the resource group cannot be found, or it cannot be disambiguated, this value should be set.
- `virtual_network_subnet_name` - If `virtual_network_name` is set, this value may also be set. If `virtual_network_name` is set, and this value is not set the builder attempts to determine the subnet to use with the virtual network. If the subnet cannot be found, or it cannot be disambiguated, this value should be set.
- `capture_name_prefix` - VHD prefix. The final artifacts will be named PREFIX-osDisk.UUID and PREFIX-vmTemplate.UUID.

### Builder variables

The `builders` section contains variables for the `azure-arm` builder used in the project. Most of the builder variables are inherited from the `user variables` section, however, the variables can be overwritten to adjust image-generation performance.

- `vm_size` - Size of the VM used for building. This can be changed when you deploy a VM from your VHD.
- `image_os` - Type of OS that will be deployed as a temporary VM.
- `image_version` - Specify version of an OS to boot from.

**Detailed Azure builders documentation can be found in [packer documentation](https://www.packer.io/docs/builders/azure).**

### Toolset

Configuration for some installed software is located in `toolset.json` files. These files define the list of Ruby, Python, Go versions, the list of PowerShell modules and VS components that will be installed to image. They can be changed if these tools are not required to reduce image generation time or image size.

Generated tool versions and details can be found in related projects:

- [Python](https://github.com/actions/python-versions/)
- [Go](https://github.com/actions/go-versions)
- [Node](https://github.com/actions/node-versions)

### Post-generation scripts

> :warning: These scripts are intended to run on a VM deployed in Azure

The user, created during the image generation, does not exist in the result VHD hence some configuration files related to the user's home directory need to be changed as well as the file permissions for some directories. Scripts for that are located in the `post-generation` folder in the repository:

- Windows: <https://github.com/actions/runner-images/tree/main/images/win/post-generation>
- Linux: <https://github.com/actions/runner-images/tree/main/images/linux/post-generation>

**Note:** The default user for Linux should have `sudo privileges`.

The scripts are copied to the VHD during the image generation process to the following paths:

- Windows: `C:\post-generation`
- Linux:  `/opt/post-generation`

#### Running scripts

- Ubuntu

  ```bash
  sudo su -c "find /opt/post-generation -mindepth 1 -maxdepth 1 -type f -name '*.sh' -exec bash {} \;"
  ```

- Windows

  ```powershell
  Get-ChildItem C:\post-generation -Filter *.ps1 | ForEach-Object { & $_.FullName }
  ```

#### Script details

##### Ubuntu

- **cleanup-logs.sh** - removes all build process logs from the machine
- **environment-variables.sh** - replaces `$HOME` with the default user's home directory for environmental variables related to the default user home directory
- **homebrew-permissions.sh** - Resets homebrew repository directory by running `git reset --hard` to make the working tree clean after chmoding /home and changes the repository directory owner to the current user
- **rust-permissions.sh** - fixes permissions for the Rust folder. Detailed issue explanation is provided in [runner-images/issues/572](https://github.com/actions/runner-images/issues/572).

##### Windows

- **GenerateIISExpressCertificate.ps1** - generates and imports a certificate to run applications with IIS Express through HTTPS
- **InternetExplorerConfiguration** - turns off the Internet Explorer Enhanced Security feature
- **Msys2FirstLaunch.ps1** - initializes bash user profile in MSYS2
- **VSConfiguration.ps1** - performs initial Visual Studio configuration