Re: If two drives are marked bootable what happens?

[Steve]

Disk boot order is set in the BIOS?

On Sat, 3 Apr 2021 at 12:31, Chris Green <cl@isbd.net> wrote:

> A friend has been having trouble with a SATA SSD that his system won't
> recognise so I have been playing with it a bit to see if I can work
> out what the problem is.
>
> This question isn't really related to the above problem.  I plugged
> the SATA SSD into a system of mine which happens to have an eSATA
> connector and 'fdisk -l' then shows:-
>
>     Disk /dev/sda: 465.8 GiB, 500107862016 bytes, 976773168 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: 0xff18eec4
>
>     Device     Boot     Start       End   Sectors   Size Id Type
>     /dev/sda1  *           63 964189169 964189107 459.8G 83 Linux
>     /dev/sda2       964189170 976768064  12578895     6G  5 Extended
>     /dev/sda5       964189233 976768064  12578832     6G 82 Linux swap /
> Solaris
>
>
>     Disk /dev/sdb: 149.1 GiB, 160041885696 bytes, 312581808 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: 0xfa947ad3
>
>     Device     Boot Start       End   Sectors   Size Id Type
>     /dev/sdb1  *     2048 312580095 312578048 149.1G 83 Linux
>
>
> The system has booted from /dev/sda1 (its internal disk drive), why does
> it
> choose to boot from this drive rather than /dev/sda1 since both are marked
> bootable?
>
> --
> Chris Green
>
>