Create a persistent disk image from an ISO file

Windows

Installation media for Windows applications is often provided as an ISO file, but Compute Engine does not let you expose an ISO file as a virtual DVD drive to a VM instance.

To access the contents of the ISO file on a single Windows VM, you can do either of the following:

Copy the ISO file to the VM and mount it locally. This approach works well if you only need to access the contents of the ISO file on a single VM instance.
Create a Persistent Disk from the ISO file and attach the disk in read-only mode to one or more VM instances. This approach works well if multiple VMs need access to the contents of the ISO file.

This document describes how you can create a Persistent Disk from the ISO file and attach the disk in read-only mode to one or more VMs.

Before you begin

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gcloud
1. Install the Google Cloud CLI, then initialize it by running the following command:
  gcloud init
  Note: If you installed the gcloud CLI previously, make sure you have the latest version by running gcloud components update.
2. Set a default region and zone.

Prepare the ISO file

If the ISO file is publicly available via HTTP, you do not need to download the ISO file first. To use a local ISO file, you can upload the ISO file to Cloud Storage.

HTTP URL

In the Google Cloud console, open Cloud Shell by clicking the Activate Cloud Shell button.

Go to the Google Cloud console
Create an environment variable for the download URL. The URL can be an HTTP or HTTPS URL, but it must be accessible anonymously.
```
ISO_URL=https://example.com/big.iso
```

Local ISO file

In the Google Cloud console, create a Cloud Storage bucket.

Go to the Google Cloud console
Upload the ISO file.

Depending on the size of the ISO file, the upload can take several minutes or hours.
In the Storage browser, navigate to the uploaded object.
On the Object details page, copy the URI of the object. The URI starts with gs://.
Open Cloud Shell by clicking the Activate Cloud Shell button.

Go to the Google Cloud console
Create an environment variable for the download URL. Replace URI with the URI that you copied.
```
ISO_URL=URI
```

Create a disk containing the contents of the ISO file

To copy the contents of the ISO file to a new disk, create a temporary VM, then create an image from the disk:

From Cloud Shell, specify the name that you want to assign to the new disk:
```
DISK_NAME=iso
```
Create a new disk to which to copy the contents of the ISO files:
```
gcloud compute disks create $DISK_NAME \
  --size=10GB \
  --zone=$(gcloud config get-value compute/zone)
```
Use a larger disk size if your ISO file exceeds 9 GB.

Create a startup script for the temporary VM. The startup script performs the following actions:

Format the secondary disk with the NTFS file system.
Download the ISO file from the HTTP or Cloud Storage URL you specified.
Mount the ISO file and copy its contents to the secondary disk.

cat << "EOF" > startup.ps1

$DownloadDirectory = 'c:\download\'
$ErrorActionPreference = 'Stop'
$MetadataUrl = 'http://metadata.google.internal/computeMetadata/v1/instance'

$DownloadUrl = (Invoke-RestMethod `
    -Headers @{"Metadata-Flavor" = "Google"} `
    -Uri "$MetadataUrl/attributes/iso")

mkdir $DownloadDirectory\Source -Force

Write-Host '== Formatting secondary disk... ===' -ForegroundColor Black -BackgroundColor Yellow
Set-Disk -Number 1 -IsOffline $false
Clear-Disk -Number 1 -RemoveData -Confirm:$false -ErrorAction SilentlyContinue
Initialize-Disk -Number 1 -PartitionStyle MBR
New-Partition -DiskNumber 1 -UseMaximumSize -DriveLetter D -IsActive |
Format-Volume -FileSystem 'NTFS' -Confirm:$false

Write-Host '== Downloading ISO... =============' -ForegroundColor Black -BackgroundColor Yellow
if ($DownloadUrl.StartsWith('gs:')) {
    & gcloud storage cp $DownloadUrl "$DownloadDirectory\Source\image.iso" | Out-Default
}
else {
    Import-Module BitsTransfer
    Start-BitsTransfer -Source $DownloadUrl -Destination "$DownloadDirectory\Source\image.iso"
}

Write-Host '== Mounting ISO... ================' -ForegroundColor Black -BackgroundColor Yellow
Mount-DiskImage -ImagePath "$DownloadDirectory\Source\image.iso" -StorageType ISO

Write-Host '== Copying ISO contents... ========' -ForegroundColor Black -BackgroundColor Yellow
Copy-Item 'e:\*' 'd:\' -Force -Recurse -PassThru `
    | Where-Object { -Not $_.PSIsContainer } `
    | Set-ItemProperty -Name IsReadOnly -Value $False

Write-Host '== Completed. =====================' -ForegroundColor Black -BackgroundColor Yellow
Invoke-RestMethod `
    -Headers @{'Metadata-Flavor'='Google'}  `
    -Method PUT  `
    -Uri "$MetadataUrl/guest-attributes/vm/ready" `
    -Body true
EOF

Create a Windows Server 2019 VM that uses the startup script and the disk that you created previously:

gcloud compute instances create iso-copier \
    --machine-type=n1-standard-2 \
    --image-family=windows-2019-core \
    --image-project=windows-cloud \
    --disk=name=$DISK_NAME,auto-delete=no \
    --metadata=enable-guest-attributes=true,iso=$ISO_URL \
    --metadata-from-file=windows-startup-script-ps1=startup.ps1 \
    --scopes=https://www.googleapis.com/auth/devstorage.read_only

The VM takes about 2 minutes to start. Depending on the size of the ISO file, it can take another 5-15 minutes for the file copy operation to complete. You can observe the progress by running the following command:

gcloud compute instances tail-serial-port-output iso-copier \
    --zone=$(gcloud config get-value compute/zone)

Wait for the VM to finish running the startup script:

until gcloud compute instances get-guest-attributes iso-copier \
    --zone=$(gcloud config get-value compute/zone) \
    --query-path=vm/ready > /dev/null 2>&1
do
    sleep 5 && echo waiting for VM to finish...
done

Shut down and delete the VM:
```
gcloud compute instances delete iso-copier \
    --zone=$(gcloud config get-value compute/zone) \
    --quiet
```
Notice that the secondary disk is not deleted because it was mounted with the parameter auto-delete=no.

The disk is now ready to be used. You can attach the disk in read-only mode to one or more VM instances within the same zone.

Share the disk across zones and regions by creating an image

To make the contents of the ISO file available in other zones or regions, create a Compute Engine image:

From Cloud Shell, create an image from the disk that you created in the previous section:

gcloud compute images create $DISK_NAME \
    --source-disk=$DISK_NAME \
    --source-disk-zone=$(gcloud config get-value compute/zone)

Clean up

To avoid incurring further costs after you have completed this process, you can delete the resources that you created:

Delete the disk:

gcloud compute disks delete $DISK_NAME \
    --zone=$(gcloud config get-value compute/zone) \
    --quiet

Delete the image:

gcloud compute images delete $DISK_NAME

What's next

Learn how to create custom images.
Learn how to manage access to custom images.
Learn more about Windows workloads on Compute Engine.