The warning triggers because the VM configuration includes a virtual serial port (COM port), but the hypervisor cannot map it to a valid physical backend. This happens for three primary reasons:
Connecting from the host:
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Here is a deep dive into why this happens and how you can fix it. Why Does This Message Appear? virtual device serial0 will start disconnected
This warning should not be mistaken for a critical system error, as it is often generated by harmless or obsolete configuration settings. Understanding this distinction is the first step toward effective remediation.
Depending on whether you actually need to use a serial port within your virtual machine, choose one of the three solutions detailed below.
When a virtual machine boots, the hypervisor reviews the configuration file (the .vmx file) and attempts to initialize all listed hardware components. The warning triggers because the VM configuration includes
If your virtual machine does not require a serial connection, the cleanest solution is to remove the device entirely. the virtual machine completely. Right-click the VM in your library and select Settings . Go to the Hardware tab. Select Serial Port (or Serial 0 ) from the device list. Click the Remove button at the bottom of the window. Click OK to save changes and restart the VM. Method 2: Disable "Connect at Power On"
Virtual serial ports serve as the communication channel between a debugee VM (the one being debugged) and a debugger VM running WinDbg or GDB. For kernel debugging, the debugee VM's serial port must be connected to a named pipe with the appropriate server/client roles. The error "Virtual device serial0 will start disconnected" in this scenario often means the named pipe could not be created or the remote debugger is not yet listening. Ensuring the debugger process is active before powering on the debugee VM resolves the issue in most cases.
The easiest way to resolve this is to remove the legacy printer device that is causing the conflict. your virtual machine completely. Open the Virtual Machine Settings . Find Printer in the list of hardware devices. Select it and click Remove . Click OK and restart the VM. Option 2: For VMware Workstation Users Why Does This Message Appear
Navigate to your VM's folder on your hard drive and locate the Open it with a text editor like Search for lines starting with If you see serial0.fileType = "thinprint" , you can safely delete all lines or change serial0.present the file and try powering on again. Method 3: Fixing Real Serial Connections If you actually
While it usually doesn’t prevent the guest OS from booting, it can be an annoying hurdle—especially if you need console access or simply want a clean, error-free startup. Why is this happening?