Re: [gentoo-user] Fun with systemd-boot

[Michael <confabulate@kintzios.com>]

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On Wednesday 18 December 2024 21:31:42 GMT Alan Mackenzie wrote:
> Hello, Michael.
> 
> Thanks for the reply.
> 
> On Wed, Dec 18, 2024 at 15:58:14 +0000, Michael wrote:

> > On an OpenRC system without GRUB, rEFInd is a good choice, or for a
> > totally
> > manual approach use the efibootmgr:
> > 
> > https://wiki.gentoo.org/wiki/Efibootmgr
> 
> I got efibootmgr installed on one of my machines.  Somebody (tm) should
> tell the maintainers that "File or directory not found" is an incomplete
> error message.  It cost me around an hour till I figured out it was
> trying to access files on /dev/sda1 (which I don't have).

When you run efibootmgr with no options it accesses the UEFI BIOS menu stored 
on the MoBo's EEPROM and displays its entries in the terminal.  It does not 
access the disk.  When you create an entry it will verify the fs path and 
kernel image you are adding on the boot menu actually exists on the fs - in 
this case it will try to read the contents of the FAT32 fs on the disk, but 
should only access the disk and partition you tell it to access when creating 
EFI boot menu entries, e.g.:

efibootmgr --create --disk /dev/sda --part 1 ... 
efibootmgr --create --disk /dev/nvme0n1 --part 3 ...

It is just a CLI tool to interact with the UEFI firmware API.  It is the UEFI 
firmware itself which is probing block devices, reading and writing on its 
EEPROM.

You'll have to copy your own kernel images on the FAT32 /efi or /boot 
partition, or use 'make install'.


> Also, none of the documentation was explicit in saying that with
> efibootmgr, you have to go into the BIOS setup to select the kernel you
> want to boot.  Nothing wrong with that, but if I'd know first, I wouldn't
> have bothered getting it working.  (Sorry, it's been a strenuous
> evening.)

Yes, you can enter the MoBos BIOS menu, if you prefer to, or you can specify/
edit your own preferred order of the UEFI boot menu entries:

--bootorder 5,2,4

or you can select which menu entry to boot next into before you reboot:

--bootnext 00005


> rEFInd doesn't feel right, somehow.  It seems to involve a graphics
> screen, and configuring icons in a config file.  I just want want to get
> the system booted, with a choice of kernels at boot time, and not have
> all the overhead of graphics and "flexibility".
> 
> I thought systemd-boot was OK, until it starting emptying my /boot
> partition, and booting from a partition other than the one I'd told it
> to.  Don't we just love software which is clever?
> 
> <Sigh>.  It looks like I'm going to have to make some compromises,
> somewhere.  It's a pity lilo isn't still going.

There is sys-boot/elilo available for UEFI systems, but it hasn't been touched 
for more than 10 years.  I've never tried it, but this doesn't mean it won't 
work as is.

There's also syslinux, but you'll need to use efibootmgr (once) to let the 
UEFI firmware know about the syslinux image.

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