Virtual Device Serial0 Will Start Disconnected <2024>

When a virtual machine starts with the warning "Virtual device serial0 will start disconnected," it typically means the VM is trying to initialize a serial port that is either misconfigured, pointing to a non-existent physical resource, or linked to a legacy feature that is no longer supported. Core Causes of the Warning

ThinPrint Feature Removal: The most common reason in modern versions of VMware Workstation (17.5+) and VMware Fusion (13.5+) is the removal of the ThinPrint virtual printing feature. These newer versions no longer support the ThinPrint protocol, which often utilized serial0.

Missing Host Resources: The VM configuration might be set to map serial0 to a physical COM port on the host machine that is currently in use by another application or simply does not exist.

Disconnected on Power On: The "Connect at power on" option for the serial device may be unchecked in the VM settings, triggering a notification that it will remain inactive. How to Resolve the Warning

Depending on your needs, you can either remove the device entirely or reconfigure it to clear the error. Option 1: Remove the Printer Device (Recommended)

If you do not explicitly use virtual printing, removing the legacy device is the cleanest fix. Power off the virtual machine completely. Open Edit Virtual Machine Settings. virtual device serial0 will start disconnected

Select the Printer or Serial Port device associated with serial0. Click Remove and save the changes. Option 2: Edit the VMX Configuration File

For advanced users or situations where the GUI does not show the device (common in Fusion or Workstation updates), you can manually remove the entries from the .vmx file.

Locate your VM's folder and open the .vmx file with a text editor. Find and delete the following lines if they exist: serial0.fileType = "thinprint" serial0.fileName = "thinprint" serial0.present = "TRUE" Save the file and restart the VM. Option 3: Disable "Connect at Power On"

If you want to keep the device but stop the warning, you can tell VMware not to attempt a connection during boot.

In the VM settings, go to the Serial Port section and uncheck Connect at power on. This will stop the system from checking for the resource every time it starts. Why this happens with Printers When a virtual machine starts with the warning

Legacy VMware versions automatically added a virtual printer that used a virtual serial port to communicate with host drivers. Because Broadcom/VMware discontinued ThinPrint, the software identifies a device it can no longer operate, resulting in the "start disconnected" status. AI responses may include mistakes. Learn more VMware Cannot Connect the Virtual Device sata0:1 Error

Here’s a draft feature covering the behavior where virtual device serial0 will start disconnected. You can use this in release notes, documentation, or a changelog.

4. Scenario C: GNS3 / Cisco Dynamips Users

This is very common for network emulation users. GNS3 often links virtual routers to VMware VMs via named pipes for console access.

The Fix:

  1. Order of Operations: The named pipe must exist before the VM looks for it. Ensure your GNS3 topology is started and the router/device linked to the VM is running before you power on the VMware VM.
  2. Check Pipe Name: Verify that the named pipe in the VMware Serial Port settings matches exactly what GNS3 expects. (e.g., \\.\pipe\gns3_link).

Scenario D: You actually NEED the Serial Port

If you are an embedded developer or network engineer requiring the serial port for debugging: Order of Operations: The named pipe must exist

  1. Go to VM Settings > Serial Port.
  2. Instead of "Use physical serial port," change the setting to "Use output file" or "Use named pipe".
  3. This prevents VMware from looking for a physical hardware port on your motherboard (which you likely don't have) and instead creates a virtual bridge.
    • Example for Named Pipe: \\.\pipe\com_1 (Server application).

Case Study: A Real-World Lab Failure

A student attempted to build a Frame Relay switch using a Cisco 3640 in GNS3. After configuring the Frame Relay map statements and inverse ARP, the PVCs remained inactive. The student spent six hours checking DLCI numbers and encapsulation types.

The root cause? The console log from boot clearly showed: "Virtual device serial0 will start disconnected" and "Virtual device serial1 will start disconnected". The student had never connected the cables from the router to the Frame Relay switch.

Moral of the story: Always read the console boot messages. That "disconnected" line is not a warning; it is a direct status report.

2. Backing is Set to "Use Physical Port (Autodetect) – Disconnected"

In VMware Workstation, when you edit VM settings, you can choose:

If you select "Physical serial port" but leave the "Connect at power on" box unchecked, you will see this message.

4. Scenario Specifics & Troubleshooting

Advanced: Tuning Emulator Performance Regarding Serial Interfaces

If you are building massive topologies (e.g., 50+ routers for CCIE studies), seeing "virtual device serial0 will start disconnected" for every single router can clutter your console logs. Here is how to mute or manage it:

How to Connect

You can connect to serial0 post-launch using one of the following methods: