Re: How make boot loader or kernel on USB stick use another device as root FS, e.g. a BIOS-unsupported PCIe NVME SSD?

On Feb 1, 2018 7:59 AM, Stuart Henderson <stu@spacehopper.org> wrote:
>
> On 2018-02-01, tinkr@openmailbox.org <tinkr@openmailbox.org> wrote:
> > Hi, so, this question sprung from the previous email however it's a big
> > one and so deserves to be addressed separately:
> >
> > If a machine's BIOS does not support booting from a particular boot
> > medium where OpenBSD is installed, e.g. my BIOS does maybe not
> > supporting booting from PCIe NVME SSD:s, but it does support booting
> > from USB memory sticks.
> >
> > For such situations, how can I create an OpenBSD USB stick boot disk,
> > that continues the OpenBSD boot process for me but from the PCIe NVME
> > SSD-stored crypto softraid?
> >
> > This could be done either by
> >
> >  * The OpenBSD kernel being stored on the USB stick, loading from it,
> >    and then using the PCIe NVME SSD as both root disk, swap disk, and
> >    dump disk, or,
>
> I think this should be possible with a custom kernel to set the
> devices. Updates will be annoying and it will be tough to get KARL
> to work nicely.
>
> >  * The OpenBSD boot loader which is stored on the USB memory stick,
> >    would load the OpenBSD kernel from the PCIe NVME SSD.
>
> The boot loader uses BIOS IO functions, if those can't talk to the
> NVME it's not going to work.
>
> > This should be a fundamental and trivial usecase to OpenBSD, however,
> > last time I tried (then with adding a "boot" command to boot.conf per
> > http://man.openbsd.org/boot.conf ), I think it not worked out of the
> > box.
>
> It might not be very appealing but afaict the only trivial way to do
> this is to place root on the USB stick or some other device, and other
> filesystems on NVME.
>
>

My root partition recently died. I did a full install on a USB stick. After booting from the stick I would then mount the other partitions from the hard drive. It was really annoying.