Use Azure VM Image Builder for Linux VMs to access an existing Azure virtual network

Applies to: ✔️ Linux VMs ✔️ Flexible scale sets

This article shows you how to use Azure VM Image Builder to create a basic, customized Linux image that has access to existing resources on a virtual network. The build virtual machine (VM) you create is deployed to a new or existing virtual network that you specify in your subscription. When you use an existing Azure virtual network, VM Image Builder doesn't require public network connectivity.


Set variables and permissions

For this task, you use some pieces of information repeatedly. Create some variables to store that information.

# set your environment variables here!!!!

# destination image resource group

# location (see possible locations in main docs)

# your subscription
# get the current subID : 'az account show | grep id'
subscriptionID=$(az account show --query id --output tsv)

# name of the image to be created

# image distribution metadata reference name

# VNET properties (update to match your existing VNET, or leave as-is for demo)
# VNET name
# subnet name
# VNET resource group name
# NOTE! The VNET must always be in the same region as the Azure Image Builder service region.
# Existing Subnet NSG Name or the demo will create it

Create the resource group.

az group create -n $imageResourceGroup -l $location

Configure networking

If you don't have an existing virtual network, subnet, or network security group (NSG), use the following script to create one.

# Create a resource group

az group create -n $vnetRgName -l $location

# Create VNET

az network vnet create \
    --resource-group $vnetRgName \
    --name $vnetName --address-prefix \
    --subnet-name $subnetName --subnet-prefix

# Create base NSG to simulate an existing NSG

az network nsg create -g $vnetRgName -n $nsgName

az network vnet subnet update \
    --resource-group $vnetRgName \
    --vnet-name $vnetName \
    --name $subnetName \
    --network-security-group $nsgName
#  NOTE! The virtual network must always be in the same region as the Azure Image Builder service region.

Add an NSG rule

This rule allows connectivity from the VM Image Builder load balancer to the proxy VM. Port 60001 is for Linux, and port 60000 is for Windows. The proxy VM connects to the build VM by using port 22 for Linux, or port 5986 for Windows.

az network nsg rule create \
    --resource-group $vnetRgName \
    --nsg-name $nsgName \
    -n AzureImageBuilderNsgRule \
    --priority 400 \
    --source-address-prefixes AzureLoadBalancer \
    --destination-address-prefixes VirtualNetwork \
    --destination-port-ranges 60000-60001 --direction inbound \
    --access Allow --protocol Tcp \
    --description "Allow Image Builder Private Link Access to Proxy VM"

Disable private service policy on the subnet

Here's how:

az network vnet subnet update \
  --name $subnetName \
  --resource-group $vnetRgName \
  --vnet-name $vnetName \
  --disable-private-link-service-network-policies true 

For more information, see Azure VM Image Builder networking options.

Modify the example template and create role

After you configure networking, you can modify the example template and create a role. Here's how:

# download the example and configure it with your vars

curl -o existingVNETLinux.json
curl -o aibRoleNetworking.json
curl -o aibRoleImageCreation.json

sed -i -e "s/<subscriptionID>/$subscriptionID/g" existingVNETLinux.json
sed -i -e "s/<rgName>/$imageResourceGroup/g" existingVNETLinux.json
sed -i -e "s/<region>/$location/g" existingVNETLinux.json
sed -i -e "s/<imageName>/$imageName/g" existingVNETLinux.json
sed -i -e "s/<runOutputName>/$runOutputName/g" existingVNETLinux.json

sed -i -e "s/<vnetName>/$vnetName/g" existingVNETLinux.json
sed -i -e "s/<subnetName>/$subnetName/g" existingVNETLinux.json
sed -i -e "s/<vnetRgName>/$vnetRgName/g" existingVNETLinux.json

sed -i -e "s/<subscriptionID>/$subscriptionID/g" aibRoleImageCreation.json
sed -i -e "s/<rgName>/$imageResourceGroup/g" aibRoleImageCreation.json

sed -i -e "s/<subscriptionID>/$subscriptionID/g" aibRoleNetworking.json
sed -i -e "s/<vnetRgName>/$vnetRgName/g" aibRoleNetworking.json

Set permissions on the resource group

VM Image Builder uses the user identity provided to inject the image into Azure Compute Gallery. In this example, you create an Azure role definition that can distribute the image to the gallery. The role definition is then assigned to the user identity.

# create user assigned identity for image builder
identityName=aibBuiUserId$(date +'%s')
az identity create -g $imageResourceGroup -n $identityName

# get identity id
imgBuilderCliId=$(az identity show -g $imageResourceGroup -n $identityName --query clientId -o tsv)

# get the user identity URI, needed for the template

# update the template
sed -i -e "s%<imgBuilderId>%$imgBuilderId%g" existingVNETLinux.json

# make role name unique, to avoid clashes in the same Azure Active Directory domain
imageRoleDefName="Azure Image Builder Image Def"$(date +'%s')
netRoleDefName="Azure Image Builder Network Def"$(date +'%s')

# update the definitions
sed -i -e "s/Azure Image Builder Service Image Creation Role/$imageRoleDefName/g" aibRoleImageCreation.json
sed -i -e "s/Azure Image Builder Service Networking Role/$netRoleDefName/g" aibRoleNetworking.json

Instead of granting VM Image Builder lower granularity and increased privilege, you can create two roles. One role gives the builder permissions to create an image, and the other allows it to connect the build VM and load balancer to your virtual network.

# create role definitions
az role definition create --role-definition ./aibRoleImageCreation.json
az role definition create --role-definition ./aibRoleNetworking.json

# grant role definition to the user assigned identity
az role assignment create \
    --assignee $imgBuilderCliId \
    --role "$imageRoleDefName" \
    --scope /subscriptions/$subscriptionID/resourceGroups/$imageResourceGroup

az role assignment create \
    --assignee $imgBuilderCliId \
    --role "$netRoleDefName" \
    --scope /subscriptions/$subscriptionID/resourceGroups/$vnetRgName

For more information, see Configure Azure VM Image Builder permissions by using the Azure CLI or Configure Azure VM Image Builder permissions by using PowerShell.

Create the image

Submit the image configuration to VM Image Builder.

az resource create \
    --resource-group $imageResourceGroup \
    --properties @existingVNETLinux.json \
    --is-full-object \
    --resource-type Microsoft.VirtualMachineImages/imageTemplates \
    -n existingVNETLinuxTemplate01

# Wait approximately 1-3 mins (validation, permissions etc.)

Start the image build.

az resource invoke-action \
     --resource-group $imageResourceGroup \
     --resource-type  Microsoft.VirtualMachineImages/imageTemplates \
     -n existingVNETLinuxTemplate01 \
     --action Run 

# Wait approximately 15 mins

It can take a while to create the image and replicate it to both regions. Wait until this part is finished before moving on to creating a VM.

Create a VM

Create a VM from the image version that was created by VM Image Builder.

az vm create \
  --resource-group $imageResourceGroup \
  --name aibImgVm0001 \
  --admin-username aibuser \
  --image $imageName \
  --location $location \

Use Secure Shell (SSH) to get into the VM.

ssh aibuser@<publicIpAddress>

You should see the image was customized with a Message of the Day as soon as your SSH connection is established!

**            This VM was built from the:            **
**      !! AZURE VM IMAGE BUILDER Custom Image !!    **
**         You have just been Customized :-)         **

Clean up resources

If you want to recustomize the image version to create a new version of the same image, skip the next steps and go on to Use Azure VM Image Builder to create another image version.

The following deletes the image that was created, along with all of the other resource files. Make sure you are finished with this deployment before deleting the resources.

When you delete gallery resources, you need to delete all of the image versions before you can delete the image definition used to create them. To delete a gallery, you first need to have deleted all of the image definitions in the gallery.

Delete the VM Image Builder template:

az resource delete \
    --resource-group $imageResourceGroup \
    --resource-type Microsoft.VirtualMachineImages/imageTemplates \
    -n existingVNETLinuxTemplate01

Delete permissions assignments, roles, and identity:

az role assignment delete \
    --assignee $imgBuilderCliId \
    --role $imageRoleDefName \
    --scope /subscriptions/$subscriptionID/resourceGroups/$imageResourceGroup

az role assignment delete \
    --assignee $imgBuilderCliId \
    --role $netRoleDefName \
    --scope /subscriptions/$subscriptionID/resourceGroups/$vnetRgName

az role definition delete --name "$imageRoleDefName"
az role definition delete --name "$netRoleDefName"

az identity delete --ids $imgBuilderId

Delete the resource group:

az group delete -n $imageResourceGroup

If you created a virtual network for this quickstart, you can delete the virtual network if it's no longer being used.

Next steps

Azure Compute Galleries