How to fix the Insert CD-ROM Notification when you are not installing from CD-ROM
This fix is simple. You are running the Ubuntu server installation from a USB drive.
You get the dialog box asking for the CD-ROM…Simply remove the USB drive (that has the installation media on it) from the port that it is plugged into.
Move it to another USB Port….and the installation will find the device, think it is a CD-ROM and the install will continue.