Supervisor Upgrade Stuck on ESXi Host Due to Mounted ISO Media

Products

• VMware vSphere Kubernetes Service

Issue/Introduction

During a Supervisor upgrade, the process becomes stuck on one or more ESXi hosts and does not reflect the target upgrade version.
The upgrade does not progress past the affected host, even though other components appear healthy.

Reviewing the vSphere Lifecycle Manager (vLCM/VUM) logs shows repeated failures when attempting to place the ESXi host into maintenance mode.

Failed getting host recommendation from DRS to enter maintenance mode for cluster.
Reason: 'Currently connected device 'CD/DVD drive 1' uses backing '[] /####/####.iso', which is not accessible.'

Cause

One or more virtual machines running on the affected ESXi host have ISO images mounted to their CD/DVD drives.

The mounted ISO files are no longer accessible, which prevents the host from entering maintenance mode and blocks the Supervisor upgrade workflow.

Resolution

1. Identify virtual machines running on the affected ESXi host.
2. Check each VM for mounted CD/DVD devices.
3. Unmount any ISO images attached to the VM CD/DVD drives, or set the device to Client Device / Disconnected.
4. Once all inaccessible ISO mounts are removed, retry or allow the Supervisor upgrade to continue.

After unmounting the ISO images, the ESXi host can successfully enter maintenance mode and the Supervisor upgrade proceeds as expected.