Partition Layout:

SSD: sda1 EFI fat32 512MiB | sda2 /
HDD: sdb1 /var | sdb2 swap | sdb3 Downloads | sdb4 Old Windows MBR NTFS 512 MiB | sdb5 Windows C
HDD: sdc1 /home | sdc2 Windows Data
RAMDISK: /tmp, /run, /run/lock

All partitions tables are GPT. Both OS use EFI and GRUB boot from sda1. sdb4 is not being used.

Q1: What I want is to disable GRUB menu (only appear when pressing shift or another key) and choose my OS pressing the BIOS select device key (F10).

I tried formatting sdb4 to FAT32 and copy windows EFI files there, then from GParted flagged as boot, and esp, then updated GRUB config and run update-grub. The attempt failed, I'm unsure if I have to move sdb4 so that becomes the first partition on sdb and if windows requires something else to "set the partition as Active", from my understanding the flags boot and esp make the same effect (as Windows "Active"). The error I got was "no bootable device found". I could revert to my previous setup using Parted Magic and then running Ubuntu in recovery mode.

Q2: I would like to know if there is any disadvantage to using my BIOS device menu over GRUB, I believe GRUB is more useful while having 1 disk and many OSes.

I don't want just a copy-paste answer, I want an answer that takes me through the steps so I can understand what the solution is doing.

closed as off-topic by TheWanderer, andrew.46, David Foerster, Aaron, Eric Carvalho Oct 7 '16 at 17:14

This question appears to be off-topic. The users who voted to close gave this specific reason:

  • "This is not about Ubuntu. Questions about other Linux distributions can be asked on Unix & Linux, those about Windows on Super User, those about Apple products on Ask Different and generic programming questions on Stack Overflow." – TheWanderer, andrew.46, Aaron
If this question can be reworded to fit the rules in the help center, please edit the question.

  • Since EFI isn't part of Ubuntu, configuring EFI boot menus may off topic here. In any case one would need to know the model of your mainboard because EFI implementations differ wildly between models. – David Foerster Oct 5 '16 at 23:26
  • I opened a Meta question about this question. – David Foerster Oct 5 '16 at 23:36
  • I believe UEFI uses the gpt UUID as part of its entry to know which partition to boot from. If you run sudo efibootmgr -v and sudo blkid you will see the same long set of numbers (partition GUID). But GUID also has a code that makes it the ESP - efi system partition. en.wikipedia.org/wiki/GUID_Partition_Table – oldfred Oct 6 '16 at 1:16
  • I believe this not to be a problem, since I can use my boot menu (F10) to use other EFI shells, like from USB or in a master boot record (ie windows bootloader in MBR and ubuntu in EFI) – FreeFog Oct 6 '16 at 1:31
  • 1
    How to hide Grub-menu look in this answer – mook765 Oct 6 '16 at 5:49

EFI boots by files, not by partitions or by devices. For more information on how it works, please see:

Note that something will normally be the default boot manager, whether that's the Windows boot loader, GRUB, and EFI shell, or the fallback boot loader on an external disk. Personally, I don't see a boot to Windows, or to something of limited utility (like an EFI shell) as being a useful default in most cases. In a multi-boot environment, you probably want the default boot to be to a boot manager, which is one of GRUB's functions. If you boot to one OS most of the time, setting that OS as the default in GRUB is perfectly sensible, of course, but that's another matter.

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