Yes there is a way.
First make sure you have secure boot disabled from the firmware settings. (The menu that opens when you press f2 during boot)
Then follow the following steps:
- Press c when in grub menu to open command line
ls to list all partitions in all hard drives
my output was as follows:
(hd0) (hd0,gpt1) (hd1) (hd1,gpt8) (hd1,gpt7) (hd1,gpt6) (hd1,gpt5) (hd1,gpt4) (hd1,gpt3) (hd1,gpt2) (hd1,gpt1)
This clearly shows that my usb drive is hd0.
ls (hd0,gpt1) to confirm:
Output is as follows:
Partition hd0,gpt1: Filesystem type fat - Label `CES_X64FREV`, UUID 4099-DBD9 Partition start-512 Sectors...
(hd0,gpt1) type the address of first partition of usb disk e.g:
(hd2,gpt1). According to output of
We need the UUID shown in the above line
In place of 4099-DBD9, write UUID which you noted down earlier.
That's it, That should boot the usb drive.
From your booted Ubuntu system, open a terminal, then use the following commands :
sdXwith the actual drive, which will probably be
sda, but use disk utility to double check if you are unsure.