If you’ve recently powered on a VMware Workstation or ESXi virtual machine only to be greeted by the warning message you aren’t alone. This is a common configuration hiccup that occurs when a VM is looking for a physical or virtual serial (COM) port that the host system can’t provide.
If you configure the serial port to connect to a named pipe (used for debugging kernel-mode code or connecting two VMs) but the pipe name is wrong or the target application isn't listening, VMware will disconnect it at startup.
This comprehensive article explains exactly what this message means, why it appears, when it is a problem, and how to fix or suppress it.
If you are using ESXi, you must reload the VM configuration via the command line so the hypervisor recognizes the manual change:
If you wish to keep the device but stop the error, expand the serial port options and uncheck . virtual device serial0 will start disconnected
When setting up network‑backed serial ports or named pipes, add and test each component one at a time. Verify connectivity on the host side before powering on the VM.
Search for lines beginning with serial0 . You will typically see lines resembling the following:
Do you need to perform or connect to legacy hardware ? Which VMware product and version are you using?
The .vmx configuration file stores every setting for a VM, including all serial port definitions. Corruption or inconsistencies can result from an abrupt shutdown of VMware, an incomplete upgrade, or manual editing errors. Even a small syntax error can prevent the serial port from being properly enumerated. In some cases, the serial port configuration references a non‑existent physical device or uses incorrect parameters that VMware cannot resolve. Backing up the .vmx file before making any changes is an essential safety measure. If you’ve recently powered on a VMware Workstation
The serial port is configured to send its output to a text log file (often used for debugging kernel crashes or gathering boot logs). If that file or its target directory was deleted, renamed, or lacks write permissions, the device fails to connect.
If you think you might need the port later but want to stop the error message now, you can tell VMware to ignore it during boot. Go to > Hardware . Select Serial Port .
: Sometimes, the virtual machine's configuration file ( .vmx ) may contain outdated or incorrect parameters for the serial port, leading to the warning on startup.
The VMware error message is a common warning that appears when powering on a virtual machine (VM) in VMware Workstation, Player, or ESXi. While it usually does not prevent the guest operating system from booting, it indicates a configuration mismatch between the virtual hardware settings and the physical host machine. Verify connectivity on the host side before powering
The VM is configured to use a physical serial port (e.g., COM1 on the host) that does not exist or is unavailable.
Right-click the VM in your library and select (or go to VM > Settings ).
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