Summary of the Problem
I've created a custom ram-only Ubuntu image that refuses to boot over USB on any device. Before I encrypted it and used a loop device, it worked well. With the encryption setup, it will boot without issues from a burned DVD as long as the drive is over SATA and not USB. Initially I thought it must be a BIOS configuration issue with booting from USB, but this is not the case as it displays the same symptoms when run on any device and with legacy usb boot properly enabled. It always gets to the grub menu, so usb boot is working.
I used the answer from this post to successfully encrypt my squashfs and set it up using losetup.
This is what I get when I attempt to boot from USB or DVD attached via USB:
/init: line 7: can't open /dev/sr0: No medium found
This spams over and over again until it drops you into the initramfs cli.
Here's what I've tried with no success:
- Enabling usb_storage and many other modules in /etc/initramfs-tools/modules during boot time
- Using isolinux instead of /boot/grub.
- Referring to the linked answer (same as above), I modified the casper files to mount to /cdrom instead of /mnt.
Afraid I'm grasping at straws here with my limited understanding of the initramfs boot priories/files. Any thoughts would be appreciated!
Additional Information
os-release: Ubuntu 18.04.4 LTS
kernel: 4.15.0-91-generic