Detach Boot Disk from GCE VM

Question

I am trying to detach the Boot Disk from a GCE VM. As the VM is stopped so it should allow me to detach it but it's returning this error

UNSUPPORTED_OPERATION: Hot-remove of the root disk is not supported.

Any suggestions?

Answer 1

Updated answer

As of 24 Jan 2019, GCE added the ability to detach and reattach boot disks from stopped VMs in GA.

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Original answer (correct prior to 24 Jan 2019)

If you detach the boot disk from a stopped VM, there's no way to restart the VM back up, so that operation does not make sense.

Thus, you would need to disable the option "auto-delete boot disk" and delete the VM:

To set the auto delete state of a persistent disk in gcloud compute, use the gcloud compute instances set-disk-auto-delete command:

gcloud compute instances set-disk-auto-delete INSTANCE \

    [--auto-delete | --no-auto-delete] --disk DISK --zone ZONE

Alternatively, you can also change this setting on the VM details page from the Developers Console by clicking on the VM instance name, and then unchecking this option:

☐ Delete boot disk when instance is deleted

Answer 2

You can't hot-remove the root disk of a VM otherwise you'd render it unusable (shutdown assumes you want to start the VM at a later point). Instead, you can delete the VM instance, making sure to preserve the root disk for future use.