[arch-general] Single Drive Fresh Install (mbr/grub2) Fails to boot (can boot existing from .iso??)

[David C. Rankin]

All,

  After 7 years and 30+ installs, I thought I had seen it all. I have a new
(used) laptop, that I put a fresh 1T drive in, partitioned and loaded arch. The
laptop can't find the drive to boot? Huh? There is only a single drive in the
laptop, but it will only boot if booting from grub hd1 (instead of hd0).

  The failure isn't a "grub prefix/root" problem, the problem is the laptop
cannot even find grub to begin with when it is booting on it's own. The only way
booting happens is to boot the installer (from USB) and then "Choose existing
OS" and edit the prefix (from 0 -> 1). Which itself is wonky, because booting
from USB creates the USB thumb-drive as /dev/sdb to begin with and the hard
drive as /dev/sda where it should be.

  This is a strange laptop, it has 2 hard drive bays (HP Elite 8760w). The bios
is configured to scan both (as well as USB and PXE) for boot. I can boot the
install .iso without issue, install went fine, but in order to boot the new
install, I have to "Boot existing OS" from the .iso menu, then 'tab' and change

  hd0 0

to

  hd1 0

(I took the existing Win10 SSD out of the same bay I put this drive in - which
is also a simple mbr boot - no UEFI). The setup is dead simple (.iso is sdb below)

$ lsblk
NAME   MAJ:MIN RM   SIZE RO TYPE MOUNTPOINT
sdb      8:16   1   980M  0 disk
├─sdb2   8:18   1    40M  0 part
└─sdb1   8:17   1   792M  0 part
sr0     11:0    1  1024M  0 rom
sda      8:0    0 931.5G  0 disk
├─sda7   8:7    0   880G  0 part /home
├─sda5   8:5    0   500M  0 part /boot
├─sda1   8:1    0     1K  0 part
├─sda8   8:8    0     1G  0 part
└─sda6   8:6    0    50G  0 part /

and

$ sudo fdisk -l /dev/sda
Disk /dev/sda: 931.5 GiB, 1000204886016 bytes, 1953525168 sectors
Units: sectors of 1 * 512 = 512 bytes
Sector size (logical/physical): 512 bytes / 4096 bytes
I/O size (minimum/optimal): 4096 bytes / 4096 bytes
Disklabel type: dos
Disk identifier: 0xff7d45aa

Device     Boot      Start        End    Sectors   Size Id Type
/dev/sda1             2048 1953525167 1953523120 931.5G  5 Extended
/dev/sda5  *          4096    1028095    1024000   500M 83 Linux
/dev/sda6          1030144  105887743  104857600    50G 83 Linux
/dev/sda7        105889792 1951383551 1845493760   880G 83 Linux
/dev/sda8       1951385600 1953525167    2139568     1G 82 Linux swap / Solaris

grub is installed to /dev/sda with

grub-install --target=i386-pc /dev/sda  (no errors on install), and
grub-mkconfig -o /boot/grub/grub.cfg

  I've searched for anything related to HP laptops or this model, but only find
issues failing to boot the install CD or the newer UEFI pages like

https://wiki.archlinux.org/index.php/HP_EliteBook_840_G1.

  Has anyone encountered something similar? There is no longer a
/boot/grub/device.map file installed by grub2, but given the fact the bios isn't
seeing the drive at all for boot, I don't see how mapping hd0 to hd1 would make
a difference. Does anyone have a link or any idea what the issue may be? I'm
happy to send whatever additional information may be required. I'm ssh'ed into
the box right now, I just need to get the boot and plasma ironed out. Any ideas?
Thanks.


-- 
David C. Rankin, J.D.,P.E.