Installing on Ubuntu 21.04

I had the same problem. What I did as a work around is at the message, remove the usb drive, plug it back in and hit continue. When it rescans for the cd it succeeds and works fine after that.

Also, I just tried a Wheezy install on the same hardware, and it does not have that problem.

Thanks everyone for the suggestions. I will give them a try!

Well, I tried all the suggestions, and nothing worked. Even tried installing from a USB CD drive multiple times and no luck. It just puts the PC into an endless restart loop after the installation app finds and mounts the CD drive.

Would still like to install from a USB stick, but the installation app fails if the install CD is not in the drive. It will not let me continue.
I had no trouble installing 2.7.14 a while back from a stick (I think) but not this.

-check the md5sum of the downloaded ISO file
-write the ISO to a USB drive using win32diskimager on windows or DD on Linux
--enter the PC BIOS and disable secure boot, UEFI, enable legacy boot
--press F12 or F11 or F9 when powering on the PC with the USB inserted
--choose USB without UEFI
That will work always even if you skip the BIOS part.

My suggestion (some might not agree) is to just do a minimal debian install. Don't install anything you don't really need.

This might help you figure out why the linuxcnc stick isn't working..

Get the iso to put on a thumbdrive here:
www.debian.org/CD/netinst/

Install Debian - instructions here:
www.debian.org/releases/stable/amd64/

Jump to section 6 if you just want to get going..
OR what I do - I just install - and only look if there is a problem.

Go back and add

deb buildbot.linuxcnc.org/ stretch 2.8-rtpreempt

to /etc/apt/sources.list

run
$ apt-key adv --keyserver hkp://keys.gnupg.net --recv-key EF1B07FEE0EE663E

apt-get update
apt Install what ever desktop manager (AKA GUI ) you like.
apt install linuxcnc-uspace
apt-install linux-image-rt-amd64

Remove pulseaudio avahi-daemon modemmanager

(we don't need them interrupting things..)

Install htop and look for things running that you don't need. Different desktops install different cruft..

Some systems might need special firmware - you can find clues by running
$ dmesg
- google any errors and warnings.

Looking at dmesg and doing a lsmod can sometimes help you spot modules that you don't need loaded - you can blacklist them.

If installing Debian becomes a problem - most problems can be solved quickly with a google search.

People that want to find potential latency problems might want to install latencytop - requires changing the kernel command line.

tommylight wrote: -check the md5sum of the downloaded ISO file
-write the ISO to a USB drive using win32diskimager on windows or DD on Linux-produces a non-bootable USB drive
--enter the PC BIOS and disable secure boot, UEFI, enable legacy boot - done
--press F12 or F11 or F9 when powering on the PC with the USB inserted - F12 gives boot order. Shows no bootable devices
--choose USB without UEFI - option not available
That will work always even if you skip the BIOS part.

Installation always loops back to the detection and mounting of the CD ROM. There is no CD ROM in the system. Am I out of luck until I find one to connect? Doesn't seem to make a lot of sense since most newer systems these days do not come with CD drives.
Yes, I am a Linux noob....