[Novalug] adventures with linux on low-cost laptops

Bryan J Smith b.j.smith@ieee.org
Mon Feb 29 05:29:40 EST 2016


It's really uEFI Storage, GPT disk labels and the EFI System Partition
(ESP) in combination, inclsuing the all important "efibootmgr" command that
replaces "grub[2]-install" as you set the firmware to target GRUB instead
of installing a boot sector.

Did one at an Orlando LUG back in 2014 using a pair of 2011 era notebooks,
one Dell m-series, one Lenovo X-series.

Unfortunately something like this doesn't cast remotely, as one is in the
firmware/post.  One cannot even use a scan converter (video to data stream)
as uEFI doesn't support use VESA BIOS Extension (VBE) modes, as those use
BIOS Int10h Video modes.  And most VM technologies don't offer uEFI
firmware emulation.

So it really has to be shown in person.

-- bjs

DISCLAIMER: Sent from phone, please excuse any typos
-- 
Bryan J Smith - Technology Mercenary
b.j.smith@ieee.org - http://linkedin.com/in/bjsmith

On Feb 29, 2016 02:05, "John Franklin" <franklin@elfie.org> wrote:

> uEFI on a technical level and how to dual-boot sounds like a great topic
> for a talk.
>
> jf
> --
> John Franklin
> franklin@elfie.org
>
>
>
> On Feb 28, 2016, at 10:22 PM, Bryan J Smith via Novalug <
> novalug@firemountain.net> wrote:
>
> > pereira via Novalug wrote:
> >> It doesn't have a normal BIOS
> >
> > Legacy PC 16-bit BIOS has severe limitations.  Beyond the fact that
> > it's PC-only, and originally designed for only 20/24-bit DOS
> > addressing/extensions, it's run into severe limitations even with
> > 32-bit extensions.
> >
> > E.g., 16-bit BIOS Int13h Disk Services cannot target, during boot,
> > more than 32-bit sectors, so it is limited to 2TiB disk sizes.
> >
> >> but something called UEFI
> >
> > Every PC platform ships with 64-bit uEFI today, period.  However, most
> > ship Compatibility Support Modules (CSM) so select, legacy PC 16-bit
> > BIOS services can be provided, such as BIOS Int10h Video Selection,
> > BIOS Int13h Disk Services, etc...
> >
> >> (there was some discussion on the list about uEFI in another context:
> >
> > No, it was the exact same context actually.  ;)
> >
> > The 64-bit "native" uEFI Storage boot _requires_ the system to be
> > setup with an EFI System Partition and the actual "boot information"
> > set in the firmware itself, *never* on-disk (_no_ "boot sectors" at
> > all).  It's virtually impossible to "switch back'n forth" as the
> > boot/OS is setup completely different.
> >
> > This is something a lot of people run into issues trying to do, and I
> > have to come in and radically change their OS to change the boot.
> > Usually a rescue mode is required, and often a change of the disk
> > format (or at least a partition).
> >
> > In the case of dual-booting Windows and Linux, they _must_, _both_ use
> > the _same_ boot mode.
> >
> >> I don't know what it is except trouble
> >
> > 64-bit uEFI is what Intel-based Mac has long used (originally started
> > with 32-bit uEFI), and Windows Vista and later supports, while
> > Microsoft _requires_ all Windows 8+ systems to ship with.
> >
> > 64-bit uEFI is also what aarch64 (64-bit ARM) is standardizing for
> > Enterprise Linux, and will finally make ARM a more commodity platform
> > for end-users.
> >
> >> but eventually we managed to go to a BIOS
> >
> > You mean you enabled Legacy CSM modules in uEFI, so it emulated some
> > BIOS services.
> >
> >> and start diddling to make it double-boot, Linux/Windows 8.1.
> >> That never worked.
> >
> > Correct, because you can_not_ switch Windows 8.1 from 64-bit "native"
> > uEFI Storage boot to 16-bit legacy BIOS Int13h Disk Services.  It has
> > to be _re-installed_.  It's exceedingly _difficult_ to do it with
> > Linux too, although adding a "BIOS Boot Partition" solves the issue
> > for GRUB.
> >
> > That said ...
> >
> > I have dual-booted over _100_ uEFI systems with Windows and Linux now.
> > I have _never_ had an issue dual-booting ... _ever_.  uEFI systems
> > _solve_ 99% of the issues with dual-booting.  However, you have to
> > understand how uEFI works.  If you're ignorant, you're likely to screw
> > up your system.
> >
> > I've had to "fix" lots of those because geeks assume how things work.
> >
> >> So, we decided to nuke Windows and go pure linux.
> >
> > Too bad.  I could have easily done it.  I do it all-the-time, even
> > with Secure Boot.
> >
> >> After many mysterious steps that we could not possibly remember,
> >> we managed to put Xubuntu on it. It works, thanks to Roger. I could
> >> even install a whole slew of applications, through a script that
> >> remembers which ones I have on my main machine.
> >> The battery on this refurbished machine seems to hold up more
> >> or less well, but its life is still disappointing to me. I don't know
> what
> >> to expect from a modern, new, low-power laptop, but this ASUS
> >> gives me maybe 2 hours runtime.
> >
> > Might be the lack of driver support for the chipset/SoC power
> > management.  That happened with a lot of the AMD APU units, even some
> > Intel Atom solutions (including Celeron/Pentium "J" and "N" models,
> > that are actually Atom) in the past.
> >
> >> One lesson: get patient, helpful expertise to assist. Thank you, Roger!
> >> Another lesson: with refurbished laptops, inquire about the battery.
> >> Thanks to the various discussions on the list, in particular Brian
> >> whose sleuthing got me to purchase one more laptop than any
> >> sane person can use at the same time.
> >
> > Again, I've yet to _ever_ have an issue with native uEFI dual-boot.
> > If it works with Windows, it _will_always_ work with Linux.
> >
> > I've only found some older firmware doesn't do full uEFI.
> > So those won't boot Windows in native uEFI Storage mode either.
> >
> >
> > --
> > Bryan J Smith - http://www.linkedin.com/in/bjsmith
> > **********************************************************************
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>



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