[Solved] Is UEFI booting from a removable device with UUID possible?

KairiTech · 2014-01-14 16:42:09

[Synopsys] efibootmgr stores the UUID of the UEFISYS partition in the NVRAM. (See the caution below regarding it falling off when I boot without the USB device plugged in and how I get it back into the NVRAM.)

It just occurred to me that booting in UEFI mode from a removable device could be easily broken if there is any drive re-ordering. I can find no reference to being able to use UUID with the efibootmgr -d and -p options.

Am I correct or is it that this is just not very well documented?

Last edited by KairiTech (2014-01-20 16:12:17)

matthew02 · 2014-01-15 06:20:07

I believe that efibootmgr uses the -d and -p input to determine the GPT GUID and then actually encodes that into the boot entry. Take a look at one of your boot entries with 'efibootmgr -v', then 'ls /dev/disk/by-partuuid -l' to see the GUID and what partition it points to.

In practice, I have never needed to add a boot entry for a removable disk. I have needed to go into the UEFI settings and change the boot order at times, but if I remember correctly, the removable device has always been automatically added to the list of bootable devices.

KairiTech · 2014-01-16 02:58:05

You are absolutely correct. efibootmgr converts the UEFISYS drive/partition to a UUID reference in the NVRAM so drive re-ordering will not break a system that boots from a removable USB device.

sandy8925 · 2014-01-16 19:30:37

Yes, I have done it with GRUB.

KairiTech · 2014-01-20 16:05:04

One thing I have discovered with my ASUS M5A99X EVO mobo is that it removes the boot entry from the NVRAM when I boot without the USB device plugged in.

During the install I create a one-line script (in the same location as the kernel) containing the efibootmgr command and parameters that was used to add the boot entry to the NVRAM. That way I can manually mount the USB devise and run the script to have the boot entry added back to the NVRAM when it falls off.

TheSaint · 2014-01-20 16:14:20

For my experience, any media with EFI flag will be listed on the BIOS at boot time. Therefore DVD, CD and USB partition will be there.

KairiTech · 2014-01-20 16:27:23

TheSaint wrote:

For my experience, any media with EFI flag will be listed on the BIOS at boot time. Therefore DVD, CD and USB partition will be there.

True but with none of the kernel boot parameters.

TheSaint · 2014-01-21 16:24:56

Well, after it is just the matter to start an EFI application. Usually looking at bootx64.EFI.

KairiTech · 2014-01-21 17:16:13

TheSaint wrote:

Well, after it is just the matter to start an EFI application. Usually looking at bootx64.EFI.

I think I'm at fault here for not fully explaining what I've done.

I'm booting a STUB kernel without a bootloader into a fully functional desktop installed on a LUKS encrypted RAID0 array with LVM2 on it. By design, I moved the UEFISYS partition to the removable device so that without it plugged in my system will not boot. root remains of the internal drives.

bootx64.EFI would just get me to the shell. If I could figure out how to get the kernel boot parameters into bootx64.EFI that would be fantastic but I haven't read anything that would make me believe it's even possible when booting a STUB kernel and not a bootloader.

Last edited by KairiTech (2014-01-21 17:20:26)

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#1 2014-01-14 16:42:09

[Solved] Is UEFI booting from a removable device with UUID possible?

#2 2014-01-15 06:20:07

Re: [Solved] Is UEFI booting from a removable device with UUID possible?

#3 2014-01-16 02:58:05

Re: [Solved] Is UEFI booting from a removable device with UUID possible?

#4 2014-01-16 19:30:37

Re: [Solved] Is UEFI booting from a removable device with UUID possible?

#5 2014-01-20 16:05:04

Re: [Solved] Is UEFI booting from a removable device with UUID possible?

#6 2014-01-20 16:14:20

Re: [Solved] Is UEFI booting from a removable device with UUID possible?

#7 2014-01-20 16:27:23

Re: [Solved] Is UEFI booting from a removable device with UUID possible?

#8 2014-01-21 16:24:56

Re: [Solved] Is UEFI booting from a removable device with UUID possible?

#9 2014-01-21 17:16:13

Re: [Solved] Is UEFI booting from a removable device with UUID possible?

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