Re: Booting an old PC to SSD that the BIOS cannot see

[Chris Green]

On Tue, Dec 29, 2020 at 03:33:50PM -0800, Robert Furber via Support requests 
for the GRand Unified Bootloader wrote:
> On 2020-12-29 1:31 a.m., Pascal Hambourg wrote:
> > Le 29/12/2020 à 04:54, Robert Furber via Support requests for the GRand
> > 
> > No. GRUB relies either on platform (BIOS/UEFI) drivers or GRUB's own
> > native drivers (not enabled by default). AFAIK GRUB does not have a
> > native NVMe driver either (yet).
> > 
> > If the adapter card does not provide an expansion ROM for the platform
> > firmware, your only option is to install /boot and GRUB (for BIOS boot)
> > or the EFI partition (for EFI boot) on a drive that the BIOS can manage
> > and boot from.
> Hmmmmm.. It is an old (2012) PC with BIOS. To my knowledge, it is not aware
> of UEFI and the BIOS is not aware of the PCIe NVMe SSD. However, after
> booting, Gparted can see the NVMe SSD and I can copy files to it (after
> partitioning and formatting).
> 
It's the Linux kernel drivers that allow you to see the nvme disk.


> So, now I am confused as to who does the booting. Before booting my PC
> cannot see the NVMe SSD, but it can see it after booting. Ergo, booting
> brought about this awareness on the PC. Is it that Grub only does part of
> the booting and some other software initializes hardware ..hardware such as
> the NVMe SSD? In other words, is it Grub and Company that look after
> bringing up the PC to full operation? Where can I learn about this?
> 
Here! :-)


> Presumably I can put /boot on /dev/sda and '/' and '/home' on /dev/nvme.. as
> per Chris Greene, if I understand correctly?
> 
Here's how my system like yours is partitioned:-

    Filesystem     Type 1M-blocks   Used  Avail Use% Mounted on
    /dev/nvme0n1p2 ext4     48174  11681  33978  26% /
    /dev/nvme0n1p3 ext4    896193 313911 536690  37% /home
    /dev/sdb1      ext4     10016    176   9313   2% /boot
    /dev/sdb2      ext4    109596  27675  76313  27% /scratch
    /dev/sda1      ext4    938772 220811 670252  25% /bak

> Even so, booting done by Grub & Co. is a ton of work, consuming about 30s.
> Would there be any way to speed up booting time by doing part of the
> initialization from /dev/sda, the HDD and the heavy lifting from
> /dev/nvme.., sthe SSD?
> 
Mine boots pretty fast, /dev/sdb is what *used* to be my system disk
and is a SATA SSD but my first pass at sorting this out had boot on a
spinning hard disk and while it is somewhat faster on the SATA SSD it
doesn't make a huge difference.  There's not much has to be read off
/boot.

-- 
Chris Green