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How to bring a Linux custom image from your physical lab environment
Describes how to bring a Linux custom image from your physical lab environment.
07/27/2021
how-to

Bring a Linux custom image from your physical lab environment

The steps in this article show how to import a Linux custom image that starts from your physical lab environment. With this approach, you create a VHD from your physical environment and import the VHD into a compute gallery so that it can be used within Azure Lab Services. Before you use this approach for creating a custom image, read Recommended approaches for creating custom images to decide which approach is best for your scenario.

Azure endorses a variety of distributions and versions. The steps to bring a custom Linux image from a VHD varies for each distribution. Every distribution is different because each one has unique prerequisites that must be set up to run on Azure.

In this article, we'll show the steps to bring a custom Ubuntu 16.04\18.04\20.04 image from a VHD. For information on using a VHD to create custom images for other distributions, see Generic steps for Linux distributions.

Prerequisites

You'll need permission to create an Azure managed disk in your school's Azure subscription to complete the steps in this article.

When you move images from a physical lab environment to Lab Services, restructure each image so that it only includes software needed for a lab's class. For more information, read the Moving from a Physical Lab to Azure Lab Services blog post.

Prepare a custom image by using Hyper-V Manager

The following steps show how to create an Ubuntu 18.04\20.04 image from a Hyper-V virtual machine (VM) by using Windows Hyper-V Manager.

  1. Download the official Linux Ubuntu Server image to your Windows host machine that you'll use to set up the custom image on a Hyper-V VM.

    If you are using Ubuntu 18.04 LTS, we recommend using an image that does not have the GNOME or MATE graphical desktops installed. GNOME and MATE currently have a networking conflict with the Azure Linux Agent which is needed for the image to work properly in Azure Lab Services. Instead, use an Ubuntu Server image and install a different graphical desktop, such as XFCE. Another option is to install GNOME\MATE using a lab's template VM.

    Ubuntu also publishes prebuilt Azure VHDs for download. These VHDs are intended for creating custom images from a Linux host machine and hypervisor, such as KVM. These VHDs require that you first set the default user password, which can only be done by using Linux tooling, such as qemu, which isn't available for Windows. As a result, when you create a custom image by using Windows Hyper-V, you won't be able to connect to these VHDs to make image customizations. For more information about the prebuilt Azure VHDs, read Ubuntu's documentation.

  2. Start with a Hyper-V VM in your physical lab environment that was created from your image. For more information, read the article on how to create a virtual machine in Hyper-V. Set the settings as shown here:

    • The VM must be created as a Generation 1 VM.

    • Use the Default Switch network configuration option to allow the VM to connect to the internet.

    • In the Connect Virtual Hard Disk settings, the disk's Size must not be greater than 128 GB, as shown in the following image.

      :::image type="content" source="./media/upload-custom-image-shared-image-gallery/connect-virtual-hard-disk.png" alt-text="Screenshot that shows the Connect Virtual Hard Disk screen.":::

    • In the Installation Options settings, select the .iso file that you previously downloaded from Ubuntu.

    Images with a disk size greater than 128 GB are not supported by Lab Services.

  3. Connect to the Hyper-V VM and prepare it for Azure by following the steps in Manual steps to create and upload an Ubuntu VHD.

    The steps to prepare a Linux image for Azure vary based on the distribution. For more information and specific steps for each distribution, see distributions and versions.

    When you follow the preceding steps, there are a few important points to highlight:

    • The steps create a generalized image when you run the deprovision+user command. But it doesn't guarantee that the image is cleared of all sensitive information or that it's suitable for redistribution.

    • The final step is to convert the VHDX file to a VHD file. Here are equivalent steps that show how to do it with Hyper-V Manager:

      1. Go to Hyper-V Manager > Action > Edit Disk.
      2. Locate the VHDX disk to convert.
      3. Next, choose to Convert the disk.
      4. Select the option to convert it to a VHD disk format.
      5. For the Disk Type, select Fixed size.
        • If you also choose to expand the disk size at this point, make sure that you do not exceed 128 GB. :::image type="content" source="./media/upload-custom-image-shared-image-gallery/choose-action.png" alt-text="Screenshot that shows the Choose Action screen.":::

To help with resizing the VHD and converting to a VHDX, you can also use the following PowerShell cmdlets:

Upload the custom image to a compute gallery

  1. Upload the VHD to Azure to create a managed disk.

    1. You can use either Azure Storage Explorer or AzCopy from the command line, as shown in Upload a VHD to Azure or copy a managed disk to another region.

      [!WARNING] If your machine goes to sleep or locks, the upload process might get interrupted and fail. Also, make sure that when AzCopy completes, that you revoke SAS access to the disk. Otherwise, when you attempt to create an image from the disk, you'll see the error "Operation 'Create Image' is not supported with disk 'your disk name' in state 'Active Upload'. Error Code: OperationNotAllowed*."

    2. After you've uploaded the VHD, you should now have a managed disk that you can see in the Azure portal.

      You can use the Azure portal's Size+Performance tab for the managed disk to change your disk size. As mentioned before, the size must not be greater than 128 GB.

  2. In a compute gallery, create an image definition and version:

    1. Create an image definition:

      • Choose Gen 1 for the VM generation.
      • Choose Linux for the Operating system.
      • Choose generalized for the Operating system state.

      For more information about the values you can specify for an image definition, see Image definitions.

      You can also choose to use an existing image definition and create a new version for your custom image.

    2. Create an image version:

      • The Version number property uses the following format: MajorVersion.MinorVersion.Patch. When you use Lab Services to create a lab and choose a custom image, the most recent version of the image is automatically used. The most recent version is chosen based on the highest value of MajorVersion, then MinorVersion, and then Patch.
      • For the Source, select Disks and/or snapshots from the dropdown list.
      • For the OS disk property, choose the disk that you created in previous steps.

      For more information about the values you can specify for an image version, see Image versions.

Create a lab

Create the lab in Lab Services and select the custom image from the compute gallery.

If you expanded the disk after the OS was installed on the original Hyper-V VM, you might also need to extend the partition in Linux's filesystem to use the unallocated disk space. Log in to the lab's template VM and follow steps similar to what is shown in Expand a disk partition and filesystem.

The OS disk typically exists on the /dev/sad2 partition. To view the current size of the OS disk's partition, use the command df -h.

Next steps