Arch Linux

anacron

Member

Registered: 2020-01-26

Posts: 40

UEFI-only installation medium?

I created my own personalized installation medium with archiso. It's based on the "releng" profile but has a few more packages.

I'm currently using it to install to a VPS, and the problem is that it always boots in BIOS mode, even though the support staff insists that my VPS has been configured for UEFI boot. I know that the ISO is capable of booting in either mode, because I've used this same archiso profile for UEFI installations.

Question: Is it possible to reconfigure archiso to disable BIOS boot and thus force my VPS to boot in UEFI mode?

Last edited by anacron (2026-04-22 14:39:29)

cryptearth

Member

Registered: 2024-02-03

Posts: 2,135

Re: UEFI-only installation medium?

no, because it's not the the boot medium which sets the boot mode but the firmware
if it boots legacy then it's confugured this way - nothin a boot media could change

anacron

Member

Registered: 2020-01-26

Posts: 40

Re: UEFI-only installation medium?

Okay, thanks for the info.

In that case, how can I politely prove to the staff that they're wrong about it being in UEFI mode?

cryptearth

Member

Registered: 2024-02-03

Posts: 2,135

Re: UEFI-only installation medium?

just open a support ticket

Head_on_a_Stick

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From: The Wirral

Registered: 2014-02-20

Posts: 9,003

Website

Re: UEFI-only installation medium?

how can I politely prove to the staff that they're wrong about it being in UEFI mode?

Ask them to check for the presence of /sys/firmware/efi/, that will only be there if the system is booted in UEFI mode.

---

Jin, Jîyan, Azadî

eznix

Member

Registered: 2020-06-29

Posts: 34

Re: UEFI-only installation medium?

Question: Is it possible to reconfigure archiso to disable BIOS boot and thus force my VPS to boot in UEFI mode?

Sure. The profiledef.sh script has this section:

bootmodes=('bios.syslinux'
           'uefi.systemd-boot')

Simply remove the 'bios.syslinux' and your iso will not have a bootloader for legacy bios systems.

cryptearth

Member

Registered: 2024-02-03

Posts: 2,135

Re: UEFI-only installation medium?

which will just cause it to fail to boot entirely

eznix

Member

Registered: 2020-06-29

Posts: 34

Re: UEFI-only installation medium?

It appears some one lost the bread crumb trail.

I suggested editing the bootmodes line in the profiledef.sh script to remove the bios.syslinux statement. This will have the effect of not installing a legacy bios compatible bootloader in the ISO. The entire point of which is to prevent the ISO from booting in a legacy bios system. If the uefi.systemd-boot statement is the only bootmode, then the ISO will boot in a UEFI system only. I thought that is what the OP desired.

A benefit of this setup is twofold. Users of the ISO will not have the option to boot and install in bios mode and be forced to boot and install in UEFI mode. This will prove they are doing it right according to the OP. And the resulting installed system will boot in UEFI mode only.

cryptearth

Member

Registered: 2024-02-03

Posts: 2,135

Re: UEFI-only installation medium?

the point of OP is/was: They were told by the hosters' staff that a vps was setup in uefi mode but was setup in legacy mode - and if it woukd be possible to chanfe that via a boot medium

only correct answer: no - because a boot medium just CAN'T change that setting

if a system, no matter if bare metal oder vm, is set to legacy it will only boot into legacy - if it's set to uefi it will bootinto uefi - it's as simple as that
the idea to create a boot medium that can be booted in either way is to provide just one image instead of maintain two different versions

as for CSM: it highly depends on the specific implementation of a platforms firmware how to behave when it encounters such a medium in such mode - but as we talk about a VM here (OP states a "VPS") the answer should(tm) be as simple as "the hoster F*ed up here" as - at least to my knowledge - vm are usually either legacy or uefi - at least i have not encountered any dual-mode/csm-capable vm implementation

it would be a different story if we would talk about bare metal - but these days when you get to the price tag of real physical hardware you usually get kvm/ipmi access and via it one has access to such setting (fun fact: i'm at ovh and when i ordered my current root it actuawally was set to legacy and i had to configure it to uefi only without a guide and just a generic manual from ASRock-rack; as for why modern server hardware still provides legacy config and why it was enabled - don't know, but i also don't have info about the systems history)

eznix

Member

Registered: 2020-06-29

Posts: 34

Re: UEFI-only installation medium?

the point of OP is/was: They were told by the hosters' staff that a vps was setup in uefi mode but was setup in legacy mode - and if it woukd be possible to chanfe that via a boot medium

only correct answer: no - because a boot medium just CAN'T change that setting

Providing a boot medium that can only boot in UEFI mode CAN force the user to change the setting in order to get the boot medium to boot. The answer is still yes.

cryptearth

Member

Registered: 2024-02-03

Posts: 2,135

Re: UEFI-only installation medium?

please re-read the entire topic from its start - you seem to miss something