Mass deploy ChromeOS Flex—WDS

These instructions assume that you already have a fully functional Microsoft Windows Deployment Services (WDS) infrastructure at your site.

What you need

ChromeOSFlex_WDS_Utilities.zip: A copy of the ChromeOSFlex_WDS_Utilities.zip file. The file contains the scripts and tools that you’ll need for the imaging process in the Windows Preinstallation Environment (WinPE) environment.
Note: the .WIM file included as part of this package may not work with very old devices that only support x86 PXE boot.
Mass deployment Image: A special Chrome OS Flex disk image designed for WDS deployment. The standard installation files do not work for mass deployment.
Note: Currently, the ChromeOS Flex mass deployable disk image is compatible only with devices that use modern UEFI boot architecture. Older machines that use BIOS or Legacy boot architecture are not supported.
Network file share:
- Approximately 40 GB of storage. The network share will host imaging scripts, ChromeOS Flex image file, and associated tools.
- A specific network account with proper read access to the network share.

Step 1: Set up network share and permission

Create network share: Using an account with proper administrative access, create a shared folder on your network. Download and unzip the contents of ChromeOSFlex_WDS_Utilities.zip to it.
Set up share and NTFS permissions: For the shared folder, assign the proper read permissions for share permissions and NT file system (NTFS) security.
1. Share Permissions—Allow Read.
2. Security—Allow Read & execute, List folder contents, and Read.
Download ChromeOS Flex mass deployment image: Download the mass deployment image.
Unzip Chrome OS Flex mass deployment image: Unzip the large .bin file to the shared network folder you created.
Edit the startnet.cmd file: In the shared network folder, find and open the startnet.cmd file. Replace the placeholders and save.
1. USERNAME—The username of the domain user that has read permissions to the network share that contains the ChromeOS Flex files.
2. PASSWORD—The password for the domain user that has read permissions to the network share that contains the ChromeOS Flex files.
3. DOMAIN NAME—Your Windows domain name.
4. \\SERVERNAME\SHARENAME—The network path of the share that contains the ChromeOS Flex files.
5. FILENAME.BIN—The name of the large .bin file.

Note: The startnet.cmd’s purpose is to launch our customized set of instructions at the start of the WinPE session. We perform a machine wipe and write the new ChromeOS Flex image to disk.

Step 2: Edit the boot image

Edit the .wim file to include the startnet.cmd file that you created.

Connect directly to the network file share server that’s hosting your ChromeOS Flex files. Use Remote Desktop Protocol (RDP), or a similar access method, to establish a direct session.
Note: The commands that you’ll use to edit the .wim file can’t be executed on a remote network share unless you’re using a remote command prompt, such as PsExec.
Launch an elevated command prompt running as administrator.
In the command prompt, change the directory to the shared network folder that contains the ChromeOS Flex files.
Still in the command prompt, mount the contents of the chromeosflex.wim file. Substitute the local share path of the folder containing the ChromeOS Flex files and the target working directory, tmp folder. Execute the command:
imagex /mountrw [path to chromeosflex.wim file] 1 [path to tmp folder]
Example: imagex /mountrw z:\deployment_share\chromeosflex\chromeosflex.wim 1 z:\deployment_share\chromeosflex\tmp
Where z:\deployment_share\chromeosflex\chromeosflex.wim is the path to the ChromeOS Flex file, and z:\deployment_share\chromeosflex\tmp is the path to tmp folder.
The imagex /mountrw command uses the imagex utility to extract, mount, and modify the contents of the chromeosflex.wim file to include your custom startnet.cmd file.
Using Windows File Explorer, copy your custom startnet.cmd file to the ..\tmp\windows\system32 folder, overwriting the previous file.
Close all File Explorer windows, notepad.exe instances, and open files that might be accessing the tmp subfolder.
Note: No files can be in use during the unmount process in the next step. Otherwise, you will see an error that refuses to unmount the .wim file.
In the command prompt, unmount the .wim file. Execute the command:
imagex /unmount /commit [local path to tmp folder]
Example: imagex /unmount /commit z:\deployment_share\chromeosflex\tmp
The imagex /unmount command uses the imagex utility to unmount and update the chromeosflex.wim file with the changes you made to include your custom startnet.cmd file.

When the custom chromeosflex.wim file is successfully unmounted, boot image editing is completed.

Step 3: Enable boot image for WDS

Set up the custom chromeosflex.wim file as an available boot image in your existing WDS infrastructure.

Note: If the working directory for the Chrome OS Flex share that you created is on a server other than the WDS server, you can copy the chromeosflex.wim file to the WDS server’s local drive. Or, it can be mapped remotely using the UNC path of the server hosting the .wim file. During the process of creating the boot image, the .wim file will be consumed by WDS and stored locally within its own structure.

Launch the Windows instance hosting your WDS infrastructure.
Open Windows Deployment Services.
Expand the server that currently hosts your PXE images.
Right click Boot Images and click Add Boot Image.
Browse to the location of your custom chromeosflex.wim file and click Next.
From our example, z:\deployment_share\chromeosflex\chromeosflex.wim.
Confirm that everything looks correct and click Next.
Observe progress. The process typically takes less than 5 minutes to complete.
Click Finish.

Now, you should see the mass deployment image listed under boot images.

Step 4: Deploy Chrome OS Flex to devices

Full installation of Chrome OS Flex erases all existing data, applications, settings, and OS that are currently on your target device. Lost data is permanently unrecoverable, even if the installation is not successful. Make sure you have the proper backups and data stored before continuing.

Select target device for Chrome OS Flex imaging.
Boot the device using PXE or network boot method. Ensure that BIOS settings properly configured:
- Network/PXE boot is available as a boot method in BIOS.
- UEFI boot is configured as the default boot method.
Depending on whether or not your environment has more than one WDS boot image defined:
- Chrome OS Flex is the only boot image available—Device boots directly into your mass deployment image. Deployment automatically proceeds.
- Multiple boot images are available—Choose your custom Chrome OS Flex image, using the arrow keys and Enter key.

When the WinPE environment is loaded, you’ll see a black command prompt letting you know that the command completed successfully. The device reboots with Chrome OS Flex installed.

If you experience issues or receive error messages during deployment, contact Chrome Enterprise support.

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