Bootable USB needs CD-ROM?
Just to note - I managed to go over this problem like this:
Once I get the "Your installation CD-ROM couldn't be mounted..." message and I'm back at the main Ubuntu Server install screen, I simply plugged the USB thumbdrive out, then plugged it in again, and then after pressing the "detect CD" option, I got "The CD-ROM autodetection was successful... The installation will now continue." ... and so the installation continued.
I usually use Rufus for USB images and when I create a bootable disk using ISO images for Ubuntu Server, it breaks at mounting CD/ROM device stage but when I change it to DD Image it works.
Ubuntu Server Install has been broken for many versions. I don't think it will ever be corrected. If you utilize utilities to create a USB installer, you should be fine. However, if you want advanced mode options such as creating a UEFI only boot media, you will have to do some extra work. Here is the easiest solution I have found. Make your UEFI boot stick, whichever method you prefer.(example is for fat file structure mounted to sbd1 - alter if you are using something else) Copy the .ISO file you downloaded to that same stick. Boot away. When you get to the CD error, do the following.
- Press Alt-F2
- Enter to start new terminal session
mkdir /media/usb
mount -t vfat /dev/sdb1 /media/usb
mount -o loop path/to/iso/file/UBUNTUSERVER.ISO /cdrom
- Press Alt-F1
- Say "No" to search again. Then click "Detect and mount CD-ROM"