On the right panel under , uncheck the box next to Connect at power on . Click OK and boot the virtual machine. Method 3: Manually Edit the VMX Configuration File
Method 2: Disconnect "Connect at Power On" (Best for Temporary Fixes)
Connects the virtual serial port to a host socket or another VM for debugging utilities like WinDbg. Click OK and boot the machine. Editing the VMX File Directly
The message "Virtual device serial0 will start disconnected" is VMware’s polite way of telling you: "Hey, you have a serial port, but nothing is plugged into it." virtual device serial0 will start disconnected
If you want to disable the feature globally to prevent this on other VMs: Go to > Preferences . Navigate to the Devices tab. Uncheck the box for "Enable virtual printers" . Option 3: Manual Edit (Advanced)
Always back up your .vmx file before making manual changes.
The message isn't exclusive to full desktop hypervisors. It pops up in other specialized areas too. On the right panel under , uncheck the
Redirects all serial output to a standard text file on your host system. Click Browse to create or select a .txt or .log file.
The configuration requires an output file or socket that is not reachable. Solutions for the "Serial0" Error
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 Click OK and boot the machine
If you need the serial port to exist for software configuration purposes, but you don't need it connected to anything immediately, you can simply stop it from trying to connect at boot. the virtual machine. Open the VM settings. Select Serial Port 1 . Uncheck the option Connect at power on . Click OK . Solution 3: Reconfigure the Serial Port
QEMU scenario:
This comprehensive article explains exactly what this message means, why it appears, when it is a problem, and how to fix or suppress it.
| Step | Action | Detailed Explanation | | :--- | :--- | :--- | | | Check Virtual Printer | In VMware, go to VM > Settings and remove the virtual printer or disable "Connect at power on". This directly addresses the most common cause. | | 2 | Inspect Host COM Port | If using a physical serial port, verify it exists in Device Manager (Windows) or as /dev/ttyS0 (Linux) and is not in use by another program. | | 3 | Verify VM Serial Port Path | In VM settings, ensure the path to the serial device is correct. Change from "Auto" to a specific path like /dev/ttyS0 . | | 4 | Check GNS3 Hardware | For GNS3 users: Verify the correct WIC (e.g., WIC-2T) is installed in the router's slot before powering on. | | 5 | Review Network Cabling | For GNS3 users: Ensure one end of the link is a "Serial DCE" cable and, if needed, the DCE side has a clock rate set. | | 6 | Explore Power Management | Rarely, host power management can interfere. In Device Manager, disable power saving for USB Root Hubs and the COM port if present. |
The warning is completely harmless.