Are you getting similar errors for like floppy0 or cdrom ?
When a physical server is converted into a virtual machine using tools like VMware vCenter Converter, the software attempts to replicate the physical hardware profile exactly. If the original server had an active serial port, the newly created VM inherits that hardware definition, even if the target ESXi host cannot support it. Does This Warning Impact Performance or Stability? In 95% of cases, no .
A: No. The warning is informational, not critical. The virtual machine will continue to operate normally, though the serial port may not be available until manually reconnected. Many users run production VMs for years with this warning appearing at every boot without any adverse effects. virtual device serial0 will start disconnected
If you are a VMware user, you might have encountered the warning message: during virtual machine (VM) startup or while checking the status of your VM.
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. Are you getting similar errors for like floppy0 or cdrom
If you don't use serial ports, delete the device. If you might use them later, leave it disconnected – your VM will run perfectly either way.
If you are running ESXi and the warning appears alongside a license restriction, check your current vSphere license: Does This Warning Impact Performance or Stability
He’d checked the .vmx files. He’d tried to force the connection, adding serial0.present = "TRUE" and serial0.startConnected = "TRUE" until his fingers went numb. But the hypervisor was stubborn. It knew there was no physical serial port on the sleek, modern host machine. It refused to bridge a gap that spanned thirty years of hardware evolution. "Just let me in," Elias whispered to the glass.
A VMware expert explained: "To get rid of the message, edit the .vmx file manually and remove 3 lines (two referencing serial0 and one additional one referencing 'thinprint')."
Most users can safely ignore the warning, especially if they are not actively using the serial port. For those who find the message persistent and wish to eliminate it, identifying the root cause through the troubleshooting steps outlined above—focusing on virtual printing configuration, license validation, host port availability, VMX file integrity, and network or firewall settings—will lead to a clean, warning‑free boot every time.
: Another application or virtualization service on the host may be using the COM port that the VM is trying to occupy.