Re: BIOS Can Not Find Disk
- Date: Fri, 1 Dec 2017 16:23:01 -0500
- From: Dan Norton <dnorton@xxxxxxxxxxxxxx>
- Subject: Re: BIOS Can Not Find Disk
On 12/01/2017 02:29 PM, Pascal Hambourg wrote:
Le 01/12/2017 à 19:57, Greg Wooledge a écrit :
On Fri, Dec 01, 2017 at 01:50:12PM -0500, Dan Norton wrote:
Disklabel type: gpt
Apparently, BIOS does not see a bootable device. In the dim past, fdisk
could set a partition as "active", which was its euphemism for
GPT disk labels don't have active/bootable partitions.
Yes they do. They even have two kinds of them.
- Partition attribute bit 2 = legacy BIOS bootable.
It is supposed to be equivalent to the boot/active flag in partition
entries of the MBR. I just wonder how a BIOS would use that, though.
- The good old boot/active flag of the GPT protective partition entry
in the MBR. Some BIOSes require it to boot a drive regardless of the
presence of a GPT disk label. It can be set with parted which
considers it as a disk flag (disk_set pmbr_boot on), or by fdisk by
forcing it to use the protective DOS/MBR disk label (-t dos).
This really sounds good. I could not figure out how to get at the
protective mbr and turn on that bit. Here's what I tried, after doing a
# fdisk -t dos /dev/sda
Command (m for help): m
a toggle a bootable flag
b edit nested BSD disklabel
c toggle the dos compatibility flag
Command (m for help): a
Selected partition 1
The bootable flag on partition 1 is enabled now.
Command (m for help): p
Disk /dev/sda: 931.5 GiB, 1000204886016 bytes, 1953525168 sectors
Units: sectors of 1 * 512 = 512 bytes
Sector size (logical/physical): 512 bytes / 512 bytes
I/O size (minimum/optimal): 512 bytes / 512 bytes
Disklabel type: dos
Disk identifier: 0x3f90eec3
Device Boot Start End Sectors Size Id Type
/dev/sda1 * 1 1953525167 1953525167 931.5G ee GPT
Command (m for help): w
The partition table has been altered.
Calling ioctl() to re-read partition table.
Re-reading the partition table failed.: Device or resource busy
The kernel still uses the old table. The new table will be used at the
next reboot or after you run partprobe(8) or kpartx(8).
# partprobe -s /dev/sda
After removing the cd and shutting down, re-booted from power-off state,
but unfortunately still got the "disk not found" message on a black screen.
The PC is simply not seeing the 1T sda, which is the only disk. It's not
even getting as far as the mbr/grub. The PC appears to be no more than 5
years old, based on the BIOS date, but it may be old enough to have a
flaky UEFI. Should I abandon the use of GPT?