Recovering a Cisco Desk Pro from a RoomOS boot loop

Overview

This guide documents an actual recovery of an original Cisco Webex Desk Pro. It is intended to help technical support teams and owners investigate a similar boot loop before concluding that the hardware must be replaced.

1. Symptoms

Following a factory reset and subsequent RoomOS installation, the Desk Pro:

• Repeatedly displayed the Cisco logo, followed by a black screen
• Flashed its front white LED continuously
• Never reached the normal user interface
• Could not be accessed over the network during the boot cycle
• Did not recover after power cycles or further hardware reset attempts

Replacement had been suggested, but the device's serial maintenance interface was still accessible.

2. What the boot log revealed

Reading the startup log over the serial console revealed that Linux was starting, but the active software image failed verification:

Verify /basemount/image2
PKG: Signature verification failed
Signature invalid!
Files in /basemount/image2 are incorrect
FAIL
Could not verify filesystem. Aborting.

This indicated a software image verification failure, rather than proving a hardware failure. The precise cause of the invalid signature was not established.

3. What you need

• A Windows laptop and a Micro-USB data cable
• Access to the Desk Pro's Micro-USB maintenance/serial port
• Silicon Labs CP210x USB-to-UART VCP driver
• PuTTY terminal application

4. Connect to the serial console

Step 1

Connect the Micro-USB maintenance port on the Desk Pro to the Windows laptop. Open Device Manager. The device may initially appear under Other devices as CP2102N USB to UART Bridge Controller with a warning symbol.

Step 2

If necessary, install the Silicon Labs CP210x driver. The interface should then appear under Ports (COM & LPT) with an assigned COM number. In this case it was COM3.

Step 3

Open PuTTY and select Serial. Use the following settings:

Click Open and observe startup output. For a saved record, enable Change Settings → Logging → All session output and capture a full boot cycle.

5. Interrupt automatic startup

During startup, the serial output displayed these messages at different stages:

Press 'b' to enter boot prompt
...
Press 'c' to stop autoboot: 2

The b prompt passed too quickly to catch reliably. At the later two-second countdown, repeatedly pressing c interrupted automatic startup and exposed an interactive bootloader prompt.

6. Inspect the installed software

The bootloader command list included selectsw, described as show/set active software. At the prompt, entering the command without arguments displayed the installed images:

selectsw

The crucial finding was that an older image was still installed. Its integrity was not independently verified before trying it.

7. Select the alternative image

With the device already failing to boot and image1 confirmed as an available alternative, the following command was entered at the bootloader prompt:

selectsw image1

The bootloader accepted the change. The device was then allowed to restart using the alternative software image.

Result: The Desk Pro successfully booted to its normal activation/setup interface. No manual firmware flashing, partition formatting or hardware replacement was needed.

8. What happened afterwards

After the initial recovery, the Desk Pro automatically began another software update. That installation completed successfully, and the device remained fully operational with a newer RoomOS interface.

This does not establish why the earlier image failed verification. It does demonstrate that the failure did not prevent the device from running a subsequent update successfully.

9. Lessons and precautions

1. Check the serial console before writing off the hardware. It may remain accessible even when networking and the normal interface do not work.
2. Read the actual boot error. A signature-verification failure is more specific than a generic boot loop.
3. Check for an alternative image. In this case, selectsw showed two installed images.
4. Do not assume the alternative image will work. It may be missing, damaged or incompatible on another device.
5. Avoid destructive bootloader commands. This recovery required only inspecting and changing the selected software image.
6. Keep a boot log. It provides evidence for diagnosis and escalation.

Bottom line: On this Desk Pro, selecting an existing working image through the serial bootloader recovered a device that otherwise appeared unusable.