Re: PXE-booting via EFI

[Lloyd Parkes <lloyd%must-have-coffee.gen.nz@localhost>]

On 14/09/22 20:34, Edgar Fuß wrote:
> This question is mostly not NetBSD-specific, but I'm not sure the answers
> I found elswhere are technically correct.
>
> When PXE-booting in legacy BIOS mode, the filename that the DHCP server
> offers in the first step is pxeboot_ia32.bin. When PXE-booting in EFI mode,
> that filename should be bootx64.efi.
>
> How can I diffentiate between the two methods in dhcpd.conf?
> Common wisdom seems to check option architecture-type = 00:07,
> but there are also fields in option vendor-class-identifier after
> "PXEclient:" that seem to differ.

I used to have extensive notes about this, but my world has become 
simpler more recently.

I use
        # This should detect BIOS or UEFI
        if substring (option vendor-class-identifier, 0, 20) = 
"PXEClient:Arch:00007" {
                filename "bootx64.efi";
        }
        elsif substring (option vendor-class-identifier, 0, 20) = 
"PXEClient:Arch:00000" {
                filename "pxeboot_ia32.bin";
        } else {
                option root-path "/srv/rescue/NetBSD/amd64/9.2";
        }

IIRC vendor-class-identifier can also tell you whether you have an ARM, 
i386, x64 etc. and whether the system is looking for an HTTP boot 
server. I don't have my full notes on hand though.

> Probably NetBSD-specific: In the second stage (PXE boot loading the kernel),
> in legacy mode, vendor-class-identifier is "NetBSD:i386:libsa", while in EFI
> mode, it seems to be "NetBSD:amd64:libsa" (note "amd64", not "x86_64").
> Is this guaranteed behaviour?

Yes. I'm quite sure that anyone changing those strings now will get 
yelled at.

One way I simplified my DHCPD configuration was to export all files 
except the initial bootstrap via NFS, which means I don't need to 
specify a filename and I just need to set the root-path. i.e. I am using 
the NetBSD netboot defaults so that my configuration is easier.

Cheers,
Lloyd