Depending on whether you actually need the serial port, you can resolve this warning using three different methods. Method 1: Remove the Serial Port (Recommended)
A virtual machine uses a configuration file (often a .vmx file) to define its hardware, such as hard drives, network adapters, and serial ports. "Serial0" refers to the first serial port ( COM1 ) assigned to the virtual machine.
Access the datastore or directory where the VM files are located via SSH, SFTP, or the datastore browser.
Alternatively, to remove it entirely via text, delete all lines starting with serial0 .
You likely accidentally added a Serial Port during the setup wizard.
If you are using ESXi, you must reload the VM configuration via the command line so the hypervisor recognizes the manual change:
Troubleshooting VMware: "Virtual device serial0 will start disconnected"
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.
The VM configuration is actively looking for a physical serial port (like a 9-pin D-sub connector) on your host computer, but your modern desktop or laptop does not have one.
Avoid binding virtual hardware directly to physical host resources. Use network-backed virtual serial ports (Virtual Serial Port Concentrators) if remote console redirection or kernel debugging is required across a cluster. This preserves vMotion compatibility and prevents resource locking during automated host migrations.
