When powering on a virtual machine (VM) in VMware Workstation, VMware Fusion, or ESXi, you may encounter a pop-up warning stating:
A: The "Virtual device serial0 will start disconnected" warning is rarely the root cause of major failures like boot loops or black screens, but it may serve as a clue. If you are experiencing an operational failure (e.g., the VM stops at a blinking cursor), check for issues such as a missing boot sector or corrupted disk files. The serial port warning is then secondary and should be addressed only after the primary boot issue is resolved.
Log into the or open VMware Workstation . Power off the target virtual machine. Right-click the VM and select Edit Settings .
Open the virtual machine while the VM is powered off. Select Serial Port from the Hardware list. In the right-hand panel, look at the Device status section. Uncheck the box next to Connect at power on . Click OK to save. Method 3: Edit the .vmx Configuration File Manually virtual device serial0 will start disconnected
Ensure the box is checked only if the target file or pipe is configured correctly. Click OK to commit the settings. Fixing the Error via the .VMX Configuration File
Save the file, close the editor, and relaunch your VMware application to power on the VM. Conclusion
If you are running ESXi and the warning appears alongside a license restriction, check your current vSphere license: When powering on a virtual machine (VM) in
) to handle "Virtual Printing" (ThinPrint). Following the removal of this feature in late 2023 updates, legacy virtual machine configurations still contain entries for it, leading to an invalid parameter error: serial0.fileType = "thinprint" How to Resolve the Issue Method 1: Using the GUI (Recommended for Workstation) Power off the virtual machine. VM Settings Select the and save your changes. : In VMware Workstation, go to Preferences and uncheck "Enable virtual printers" to prevent it globally. Broadcom support portal
: The most frequent cause in VMware is tied to the "Virtual Printing" feature. This feature is disabled by default on Windows hosts. When a virtual machine is configured to use this feature (common in VMs created with older versions of VMware), but the global setting is off, VMware generates the serial0 warning. The VM is essentially looking for a virtual printer, and when it doesn't find it, it disconnects the port assigned to it. This is precisely why a KB article states the message is a "warning for a configuration for Thinprinting feature".
If you fit these criteria, change the Serial Port connection type in VMware Settings from "Physical Serial Port" to or "Use named pipe" to route the data correctly without triggering the hardware disconnection error. Log into the or open VMware Workstation
If you are using a USB-to-Serial adapter, the host OS might not have the correct drivers (like CH340 or FTDI) installed, making the port "invisible" to the VM. How to Fix It Method 1: The Quick GUI Fix (Recommended)
Parameter "serial0.fileType" has an invalid value "Thinprint 10 Nov 2023 —