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: gptApparently, BIOS does not see a bootable device. In the dim past, fdiskcould set a partition as "active", which was its euphemism for "bootable".However now: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 backup:
# fdisk -t dos /dev/sda ... Command (m for help): m Help: DOS (MBR) 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 busyThe 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/sdaAfter 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?