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eccerr0r
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 Posted: Sat Aug 08, 2020 7:24 am Post subject: "Reinstalling" MBR -> EFI boot |
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Well, for an experienced user this isn't that big a deal but I wonder if it's worth the effort to switch over from MBR boot to EFI boot if your motherboard supports both?
Anyone do it for a specific reason? Pitfalls?
What I'm thinking is all I need to do is just build an EFI kernel with custom command line as needed, embed initramfs if needed, enable EFI in BIOS, and install it somewhere in the boot partition, which you just relabel as EFI system partition. Should boot right up, though I do wonder what EFI will do with my current MD-RAID1 boot partitions for MBR, I suspect I'll have to also convert from EXT2 to FAT as well.
Hmm. Too much risk for accidentally causing an unbootable system for limited or no value...?
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pietinger
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| Posted: Sat Aug 08, 2020 8:07 am Post subject: Re: "Reinstalling" MBR -> EFI boot |
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| eccerr0r wrote: | | [...] but I wonder if it's worth the effort to switch over from MBR boot to EFI boot if your motherboard supports both? |
No, its not worth. The only reason to switch would be if you want to have SecureBoot.
| eccerr0r wrote: | | Anyone do it for a specific reason? |
I do it for every new installation because it is the future (and I want to have SecureBoot). |
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NeddySeagoon
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| Posted: Sat Aug 08, 2020 8:14 am Post subject: |
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eccerr0r,
The only reason for doing the switch is because you need to boot from a HDD bigger than 2TiB.
Then you need a GPT partition table.
Even then you can BIOS boot mostly but its getting harder.
You cannot use EFI with a MSDOS partition table.
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eccerr0r
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| Posted: Sat Aug 08, 2020 2:43 pm Post subject: |
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Actually it depends on the EFI firmware. However, most EFI firmware that I've run across will indeed allow a ESP on MBR-partitioned disks along with the usual GPT partitioned disks (in fact, some work on El-Torito "disks" too!).
So without using canonical/redhat's keys, it's now possible to do secure boot on any EFI machine? I haven't looked into this in a long time, was annoyed at the fact you can't create your own boot image back then because mere mortals can't sign their own boot images and require the use of "third party" software if one wants to run Gentoo because there's no way to get/change the keys from/in firmware ...
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GDH-gentoo
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| Posted: Sat Aug 08, 2020 3:13 pm Post subject: |
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| eccerr0r wrote: | | Actually it depends on the EFI firmware. However, most EFI firmware that I've run across will indeed allow a ESP on MBR-partitioned disks along with the usual GPT partitioned disks (in fact, some work on El-Torito "disks" too!). |
Both are required by the UEFI specification, I believe. The ESP is marked with partition type EF in an MS-DOS formatted partition table. Whether actual firmware complies may vary, I suppose.
| eccerr0r wrote: | | So without using canonical/redhat's keys, it's now possible to do secure boot on any EFI machine? |
It depends on whether the UEFI firmware will let you enter setup mode and replace the platform and key exchange keys (if yes, the described procedure still looks scary and easy to screw up, though). |
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DONAHUE
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eccerr0r
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| Posted: Sun Aug 09, 2020 2:00 pm Post subject: |
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As far as I can tell I don't know if it's possible to change keys in my old motherboard firmware, so I guess it stops here unless if I want to switch to EFI boot for the heck of it.
As long as Linux continues to allow MBR boot and Grub is updated I suppose I'm OK. But with Linux dropping things like ISA support, I sometimes worry if MBR days are numbered...
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NeddySeagoon
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| Posted: Sun Aug 09, 2020 3:35 pm Post subject: |
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eccerr0r,
The kernel has little or no involvement in BIOS booting. It just gets loaded by your favourite boot loader.
Loadlin is out, The kernel will no longer fit on a floppy.
Lilo, grub-legacy and sys-linux will continue to work.
Does anyone still have ISA hardware to test a modern kernel?
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eccerr0r
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| Posted: Sun Aug 09, 2020 5:51 pm Post subject: |
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The problem is that the first sector in the Linux kernel image is an MBR boot sector - and that has to be 16-bit to run as that's MBR requirement. As fewer and fewer machines have MBR boot, just like ISA, will have less and less need for maintenance of that piece of code.
Likewise for Grub's MBR code.
If most new machines are EFI there's no need for the code and it will bitrot.
Main problem with ISA hardware these days is that they don't have enough RAM. IIRC the most RAM I have on any ISA machine is 1GiB, and the main ones top out at 256MB or so, which is fine running Linux but no longer enough to run a full GUI.
But that's not the specific issue. As MBR machines age out, they also will have arbitrary limitations that will likewise go the way of ISA machines.
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Ant P.
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| Posted: Mon Aug 10, 2020 10:25 am Post subject: |
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| eccerr0r wrote: | | If most new machines are EFI there's no need for the code and it will bitrot. |
Are we anticipating the ever-changing laws of physics to cause a hand-auditable amount of unchanging code running on unevolving hardware to behave wildly differently any time soon? |
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eccerr0r
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| Posted: Mon Aug 10, 2020 3:08 pm Post subject: |
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| Ant P. wrote: | | Are we anticipating the ever-changing laws of physics to cause a hand-auditable amount of unchanging code running on unevolving hardware to behave wildly differently any time soon? |
Same question could be posed to ISA hardware drivers, yet it still got yanked...
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Installing Gentoo
