Virtual Device Serial0 Will Start Disconnected Fix Jun 2026

If using a virtual serial pipe for debugging, the pipe name may be configured incorrectly. How to Fix "Virtual Device Serial0 Will Start Disconnected"

Why would a developer program an emulator to start a port disconnected? Efficiency and realism.

A virtual machine (VM) is software that mimics physical hardware. Just like an old desktop computer, a VM can include virtualized legacy ports, including parallel (LPT) and serial (COM) ports. virtual device serial0 will start disconnected

, support for "ThinPrint" (a virtual printing technology) has been discontinued. VMs created in older versions often still have a serial port configured to use this driver, which now triggers the "invalid value" warning. Resource Conflicts

config t interface serial0 no shutdown

The warning message is a frequent issue encountered by users of virtualization platforms like VMware Workstation Pro , VMware Fusion, and vSphere. This alert notifies you that a virtual serial port ( serial0 ) is assigned to the virtual machine (VM) but cannot hook up to a valid backend device on the host system upon bootup.

The serial port is configured to log output to a text file (e.g., serial.log ), but the destination path is invalid, read-only, or locked by another process. If using a virtual serial pipe for debugging,

The error indicates that your VM is configured to look for a serial (COM) port on your physical computer, but it can’t find one to "handshake" with. Because the VM can't establish this link, it simply starts with that specific virtual device disabled. Common Causes The "ThinPrint" Legacy:

If you'd like, I can give you the specific steps for VMware ESXi versus VMware Workstation. Which one are you using? A virtual machine (VM) is software that mimics

By understanding what this message means and when it requires action, system administrators can focus their efforts on truly critical issues while maintaining a healthy, efficient virtualized environment.

| Platform | Typical Reason | | :--- | :--- | | | The serial port is set to "Use named pipe" or "Use output file", but the other end (e.g., a debugger like WinDbg) hasn't connected yet. | | VirtualBox | Serial port is enabled with "Port Mode" set to "Disconnected". | | GNS3 / EVE-NG | The virtual router or switch has a serial interface (e.g., serial0/0 ), but it's not linked to another device's serial interface via a cable. | | QEMU | The -serial option is used without a backend (e.g., -serial null or -serial unix:/path,server=off ). |