Comment 19 for bug 500822

Failure booting from USB using ubuntu-12.04.3-desktop-i386.iso on a Dell Inspiron 9300:
- Repeated "/init: line 7: can't open /dev/sr0: No medium found" over and over
- Error: Unable to find a medium containing a live file system
- Drops into shell prompt: (initramfs)

The USB was made with a direct "dd" onto the USB key: dd if=ubuntu-12.04.3-desktop-i386.iso of=/dev/sdb
(Same errors happened with a USB key loaded using some other Windows USB creator utility.)

Solution:
- Use F6 to interrupt the boot.
- Optional: remove the keywords "quiet splash" from the kernel line.
- Add the keywords "break debug" to the kernel line and continue the boot.
- Part way into the boot, it will drop to the "(initramfs)" prompt.
- Doing "ls -l /dev/sd*" will show only sda devices - no sdb devices.
- Wait a few minutes. Various messages will print. Keep waiting.
- After a few minutes, doing "ls -l /dev/sd*" will show the USB key (sdb* devices).
- Now, exit the shell and continue the boot.
- It comes up fine.

Seems to be a timing issue with getting the USB /dev/sdb* devices recognized right after boot. Adding the break and debug (probably only one of these is actually needed but I don't know which) slows down the process and waits long enough so that the USB device can be found by the kernel correctly.