Re: If two drives are marked bootable what happens?

[Narcis Garcia]

All plugged devices can be marked as bootable (HD, FD, SSD, USB, CD/DVD,
etc.). Bootable does not mean required to boot.

BIOS does its own devices census, and sorts them to look one by one, if
it's marked as bootable. In this BIOS' sorted list, when it finds one
bootable jumps to run its loader/program/system.


Narcis Garcia

El 3/4/21 a les 13:31, Chris Green ha escrit:
> 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?
>