Modern operating systems and software rarely rely on serial communication. If you do not explicitly use legacy hardware debugging, specialized console connections, or ancient peripherals, the cleanest fix is to delete the virtual device entirely.
For debugging between two VMs, ensure the pipe name (e.g., \\.\pipe\com_1 ) matches on both ends.
To completely disable the connection at boot, change the value to false: serial0.present = "TRUE" serial0.startConnected = "FALSE" Use code with caution.
If you actually need the serial port for kernel debugging or specialized hardware, ensure the backing connection is correct.
Depending on whether you actually need the serial port, there are two main ways to handle this. Method 1: Remove the Serial Port (Recommended) virtual device serial0 will start disconnected
Or QEMU command line:
The statement “virtual device serial0 will start disconnected” typically appears in virtualization, emulation, or hardware abstraction contexts (e.g., QEMU/KVM, VirtualBox, containerized device passthrough, or network/device simulators). It means the emulated or virtual serial interface named serial0 is configured so that, at VM or system boot, it has no active connection endpoint—no host pipe, socket, file, console, or physical device attached. The device exists in the guest’s device tree but is not linked to any I/O endpoint until explicitly connected.
One VMware Fusion user reported: "Every time Fusion starts… I get this error message. This is due to Fusion 13.5 removing ThinPrint virtual printing from the product. The message is harmless (although virtual printers are no longer available in the VM)." Solutions range from ignoring it to editing the VM's configuration file to remove ThinPrint‑related lines.
), but another application is already using it, or the host does not actually have a COM1cap C cap O cap M 1 Modern operating systems and software rarely rely on
: If the Dynamips hypervisor crashes when you try to use a serial interface, try updating GNS3/Dynamips to the latest version or use a different, more stable Cisco IOS image.
If you do not need the serial port, or if it is misconfigured, telling the machine not to connect it at startup will eliminate the error. Open the virtual machine's (VM -> Settings). Click on Add/Hardware and select Serial Port . Uncheck the option "Connect at power on" . Click OK and restart the VM. 3. Remove the Unused Serial Port
If the issue persists after these generic fixes, inspect the .vmx file for configuration errors:
The VM configuration file ( .vmx ) may be instructed to map serial0 automatically to a physical COM port on the host machine. If the physical host laptop or desktop lacks a physical DB9 serial port, or if the port is disabled within the host machine’s BIOS/UEFI, initialization fails. To completely disable the connection at boot, change
Here are the most effective solutions, ordered from simplest to most complex. 1. Disable Virtual Printing (Most Common Solution)
If the device doesn't appear in the settings menu (common in Fusion 13.5+), you must manually edit the configuration file: Broadcom Community and ensure the VM is powered down. Locate your virtual machine's file (usually inside the VM bundle).
A: In Dynamips/GNS3, no. The hardware state is decided at boot. You must shut down, connect the cable, and restart the router. In EVE-NG with newer QEMU images, you may hot-plug, but it is not recommended.