Groups > linux.debian.user > #195683

Re: UEFI/"BIOS" booting, was Re: USB Install Fails, Complains about CD-ROM

From	Pascal Hambourg <pascal@plouf.fr.eu.org>
Newsgroups	linux.debian.user
Subject	Re: UEFI/"BIOS" booting, was Re: USB Install Fails, Complains about CD-ROM
Date	2018-05-13 19:10 +0200
Message-ID	<vP2Fr-5zv-13@gated-at.bofh.it> (permalink)
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Le 13/05/2018 à 17:18, David Wright a écrit :
> On Fri 11 May 2018 at 15:13:04 (-0500), Kent West wrote:
>>
>> That's good to know. I guess my source material (
>> https://www.happyassassin.net/2014/01/25/uefi-boot-how-does-that-actually-work-then/)
>> is wrong. Or I misunderstood it.
> 
> While a lot of the detail on that long page might be correct, there
> are also statements there that don't seem to agree with reality.

Most of the statements you quoted agree with my (admittedly limited) 
experience with UEFI. There is a difference between the theory 
(specifications) and the reality (implementations), and some pieces of 
software may have extra requirements beyond the sole UEFI specification.

>      "I really can’t recommend strongly enough that you do not attempt
>      to mix UEFI-native and BIOS-compatible booting of
>      permanently-installed operating systems on the same computer, and
>      especially not on the same disk. It is a terrible terrible idea
>      and will cause you heartache and pain. If you decide to do it,
>      don’t come crying to me." (under "UEFI booting: background").

I would not be as much adamant as the author, but my experience says : 
it can work, but expect trouble.

Most of my early experience with UEFI boot comes from a rather old Intel 
motherboard. Beside crippled UEFI support (no UEFI boot from USB or SATA 
in AHCI mode), it had a couple of annoying requirements :
- boot in legacy mode only if the MBR contains a partition entry with 
the boot flag set, regardless of whether the disk has a MSDOS or GPT 
partition table. This behaviour is beyond any common BIOS standard, but 
I have observed it on many other systems, mostly Dell and HP ;
- boot in EFI mode from GPT only if the protective partition entry in 
the MBR has the boot flag unset. I admit this requirement is part of the 
GPT specification, but really do not see the point in enforcing such a 
minor detail.

Anyway, these two requirements put together make it impossible to boot 
in both legacy and EFI mode from the same GPT disk with this 
motherboard. However they allow to boot in both modes from the same 
MSDOS disk. But who still wants to use MSDOS format nowadays ?

>      "Disk formats (MBR vs. GPT)
> 
>        Here’s another very important consideration:
> 
>        If you want to do a ‘BIOS compatibility’ type installation, you
>      probably want to install to an MBR formatted disk. If you want to
>      do a UEFI native installation, you probably want to install to a
>      GPT formatted disk."

I do not agree so much with this one when it comes to install GNU/Linux. 
But it is an absolute requirement when installing Windows.

>      "A specific example
> 
>      To boil down the above: if you bought a Windows 8 or later system,
>      you almost certainly have a UEFI native install of Windows to a
>      GPT-formatted disk. This means that if you want to install another
>      OS alongside that Windows install, you almost certainly want to do
>      a UEFI-native installation of your other OS. If you don’t like all
>      this UEFI nonsense and want to go back to the good old world
>      you’re familiar with, you will, I’m afraid, have to blow away the
>      UEFI-native Windows installation, and it would be a good idea to
>      reformat the disk to MBR."

I agree with the author. If you want to keep the existing EFI Windows 
installation and have a convenient dual boot with GRUB, you'll have to 
set up your favourite distribution to boot in EFI mode. If you want to 
go back to legacy boot, including for Windows, you'll have to 
repartition the disk to MSDOS format and reinstall Windows.

> I can't reconcile that with the system here, a Windows 8→10 UEFI laptop
> and GPT disk running linux in BIOS compatibility mode (here called
> Legacy mode by Lenovo) booting from an MBR on an ATA disk:

That is not very convenient, is it ? You cannot boot Windows boot 
manager from GRUB nor you can boot GRUB from Windows boot manager and 
must select the boot mode in the UEFI firmware setup whenever you want 
to switch the operating system.

> Switching over involves going through the "BIOS Setup", reached
> by a separate button (almost recessed).

As expected.

Thread

USB Install Fails, Complains about CD-ROM Kent West <westk@acu.edu> - 2018-05-11 18:20 +0200
  Re: USB Install Fails, Complains about CD-ROM Robert Menes <viewtiful.icchan@gmail.com> - 2018-05-11 18:40 +0200
    Re: USB Install Fails, Complains about CD-ROM Rick Thomas <rbthomas@pobox.com> - 2018-05-12 01:10 +0200
      Re: USB Install Fails, Complains about CD-ROM Kenneth Parker <sea7kenp@gmail.com> - 2018-05-12 03:40 +0200
      Re: USB Install Fails, Complains about CD-ROM Pascal Hambourg <pascal@plouf.fr.eu.org> - 2018-05-12 19:40 +0200
  Re: USB Install Fails, Complains about CD-ROM "Thomas Schmitt" <scdbackup@gmx.net> - 2018-05-11 18:40 +0200
  Re: USB Install Fails, Complains about CD-ROM Curt <curty@free.fr> - 2018-05-11 19:10 +0200
    Re: USB Install Fails, Complains about CD-ROM Kent West <westk@acu.edu> - 2018-05-11 20:40 +0200
  Re: USB Install Fails, Complains about CD-ROM songbird <songbird@anthive.com> - 2018-05-11 19:50 +0200
    Re: USB Install Fails, Complains about CD-ROM Kent West <westk@acu.edu> - 2018-05-11 20:40 +0200
      Re: USB Install Fails, Complains about CD-ROM Kent West <westk@acu.edu> - 2018-05-11 21:30 +0200
      Re: USB Install Fails, Complains about CD-ROM Pascal Hambourg <pascal@plouf.fr.eu.org> - 2018-05-11 22:00 +0200
        Re: USB Install Fails, Complains about CD-ROM Kent West <westk@acu.edu> - 2018-05-11 22:20 +0200
          Re: USB Install Fails, Complains about CD-ROM "Thomas Schmitt" <scdbackup@gmx.net> - 2018-05-11 22:40 +0200
            Re: USB Install Fails, Complains about CD-ROM Kent West <westk@acu.edu> - 2018-05-11 23:00 +0200
              Re: USB Install Fails, Complains about CD-ROM "Thomas Schmitt" <scdbackup@gmx.net> - 2018-05-12 00:00 +0200
              Re: USB Install Fails, Complains about CD-ROM Brian <ad44@cityscape.co.uk> - 2018-05-12 12:30 +0200
            Re: USB Install Fails, Complains about CD-ROM Pascal Hambourg <pascal@plouf.fr.eu.org> - 2018-05-12 19:50 +0200
              Re: USB Install Fails, Complains about CD-ROM "Thomas Schmitt" <scdbackup@gmx.net> - 2018-05-12 21:40 +0200
                Re: USB Install Fails, Complains about CD-ROM Pascal Hambourg <pascal@plouf.fr.eu.org> - 2018-05-13 10:20 +0200
                Re: Block sizes in ISOs. was: USB Install Fails, Complains about CD-ROM "Thomas Schmitt" <scdbackup@gmx.net> - 2018-05-13 11:30 +0200
          UEFI/"BIOS" booting, was Re: USB Install Fails, Complains about  CD-ROM David Wright <deblis@lionunicorn.co.uk> - 2018-05-13 17:20 +0200
            Re: UEFI/"BIOS" booting, was Re: USB Install Fails, Complains about  CD-ROM Pascal Hambourg <pascal@plouf.fr.eu.org> - 2018-05-13 19:10 +0200
              Re: UEFI/"BIOS" booting, was Re: USB Install Fails, Complains about  CD-ROM David Wright <deblis@lionunicorn.co.uk> - 2018-05-14 02:10 +0200
                Re: UEFI/"BIOS" booting, was Re: USB Install Fails, Complains about  CD-ROM Pascal Hambourg <pascal@plouf.fr.eu.org> - 2018-05-14 23:40 +0200
                Re: UEFI/"BIOS" booting, was Re: USB Install Fails, Complains about  CD-ROM David Wright <deblis@lionunicorn.co.uk> - 2018-05-15 04:00 +0200
              Re: UEFI/"BIOS" booting, was Re: USB Install Fails, Complains about  CD-ROM songbird <songbird@anthive.com> - 2018-05-14 12:40 +0200
                Re: UEFI/"BIOS" booting, was Re: USB Install Fails, Complains about  CD-ROM Chris Ramsden <chris.ramsden@gmail.com> - 2018-05-14 14:40 +0200
                Re: UEFI/"BIOS" booting, was Re: USB Install Fails, Complains about  CD-ROM David Wright <deblis@lionunicorn.co.uk> - 2018-05-14 16:00 +0200
                Re: UEFI/"BIOS" booting, was Re: USB Install Fails, Complains about  CD-ROM Chris Ramsden <chris.ramsden@gmail.com> - 2018-05-14 17:00 +0200
                Re: UEFI/"BIOS" booting, was Re: USB Install Fails, Complains about  CD-ROM songbird <songbird@anthive.com> - 2018-05-15 02:50 +0200
            Re: UEFI/"BIOS" booting, was Re: USB Install Fails, Complains about CD-ROM Stefan Monnier <monnier@iro.umontreal.ca> - 2018-05-14 15:20 +0200
              Re: UEFI/"BIOS" booting, was Re: USB Install Fails, Complains about  CD-ROM David Wright <deblis@lionunicorn.co.uk> - 2018-05-14 16:40 +0200
                Re: UEFI/"BIOS" booting "Thomas Schmitt" <scdbackup@gmx.net> - 2018-05-14 18:00 +0200
                Re: UEFI/"BIOS" booting Pascal Hambourg <pascal@plouf.fr.eu.org> - 2018-05-14 23:50 +0200
                Re: UEFI/"BIOS" booting "Thomas Schmitt" <scdbackup@gmx.net> - 2018-05-15 09:00 +0200
                Re: UEFI/"BIOS" booting Pascal Hambourg <pascal@plouf.fr.eu.org> - 2018-05-16 00:20 +0200
                Re: UEFI/"BIOS" booting Pascal Hambourg <pascal@plouf.fr.eu.org> - 2018-05-16 23:50 +0200
                Re: UEFI/"BIOS" booting "Thomas Schmitt" <scdbackup@gmx.net> - 2018-05-17 13:00 +0200
                Re: UEFI/"BIOS" booting, was Re: USB Install Fails, Complains about CD-ROM Stefan Monnier <monnier@iro.umontreal.ca> - 2018-05-14 18:00 +0200
                Re: UEFI/"BIOS" booting, was Re: USB Install Fails, Complains about  CD-ROM David Wright <deblis@lionunicorn.co.uk> - 2018-05-15 03:30 +0200
                Re: UEFI/"BIOS" booting, was Re: USB Install Fails, Complains about  CD-ROM Pascal Hambourg <pascal@plouf.fr.eu.org> - 2018-05-16 00:40 +0200
                Re: UEFI/"BIOS" booting, was Re: USB Install Fails, Complains about  CD-ROM David Wright <deblis@lionunicorn.co.uk> - 2018-05-18 20:40 +0200
                Re: UEFI/"BIOS" booting Pascal Hambourg <pascal@plouf.fr.eu.org> - 2018-05-14 23:50 +0200
                Re: UEFI/"BIOS" booting David Wright <deblis@lionunicorn.co.uk> - 2018-05-15 03:40 +0200
                Re: UEFI/"BIOS" booting Pascal Hambourg <pascal@plouf.fr.eu.org> - 2018-05-16 00:40 +0200
                Re: UEFI/"BIOS" booting mess-mate <eric.m.c.declerck@gmail.com> - 2018-05-16 15:20 +0200
                Re: UEFI/"BIOS" booting David Wright <deblis@lionunicorn.co.uk> - 2018-05-18 20:50 +0200
  Re: USB Install Fails, Complains about CD-ROM Mike Kupfer <mkupfer@alum.berkeley.edu> - 2018-05-13 04:20 +0200
    Re: USB Install Fails, Complains about CD-ROM Curt <curty@free.fr> - 2018-05-13 10:30 +0200
      Re: USB Install Fails, Complains about CD-ROM "Thomas Schmitt" <scdbackup@gmx.net> - 2018-05-13 12:10 +0200
        Re: USB Install Fails, Complains about CD-ROM Curt <curty@free.fr> - 2018-05-13 14:10 +0200
          Re: USB Install Fails, Complains about CD-ROM "Thomas Schmitt" <scdbackup@gmx.net> - 2018-05-13 14:50 +0200
        Re: USB Install Fails, Complains about CD-ROM Mike Kupfer <mkupfer@alum.berkeley.edu> - 2018-05-13 19:00 +0200
          Re: USB Install Fails, Complains about CD-ROM "Thomas Schmitt" <scdbackup@gmx.net> - 2018-05-13 20:20 +0200
            Re: USB Install Fails, Complains about CD-ROM Mike Kupfer <mkupfer@alum.berkeley.edu> - 2018-05-14 00:40 +0200
              Re: USB Install Fails, Complains about CD-ROM "Thomas Schmitt" <scdbackup@gmx.net> - 2018-05-14 13:30 +0200
                Re: USB Install Fails, Complains about CD-ROM Mike Kupfer <mkupfer@alum.berkeley.edu> - 2018-05-14 16:50 +0200
                Re: USB Install Fails, Complains about CD-ROM "Thomas Schmitt" <scdbackup@gmx.net> - 2018-05-14 18:20 +0200
                Re: USB Install Fails, Complains about CD-ROM David Wright <deblis@lionunicorn.co.uk> - 2018-05-14 20:10 +0200
                Re: USB Install Fails, Complains about CD-ROM "Thomas Schmitt" <scdbackup@gmx.net> - 2018-05-14 22:10 +0200
                Re: USB Install Fails, Complains about CD-ROM Mike Kupfer <mkupfer@alum.berkeley.edu> - 2018-05-14 23:00 +0200
                Re: USB Install Fails, Complains about CD-ROM Mike Kupfer <mkupfer@alum.berkeley.edu> - 2018-05-15 01:20 +0200
                Re: USB Install Fails, Complains about CD-ROM "Thomas Schmitt" <scdbackup@gmx.net> - 2018-05-15 09:10 +0200
                Re: USB Install Fails, Complains about CD-ROM Mike Kupfer <mkupfer@alum.berkeley.edu> - 2018-05-17 23:40 +0200
                Re: USB Install Fails, Complains about CD-ROM "Thomas Schmitt" <scdbackup@gmx.net> - 2018-05-18 08:50 +0200
                Re: USB Install Fails, Complains about CD-ROM Mike Kupfer <mkupfer@alum.berkeley.edu> - 2018-05-15 01:10 +0200

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