Mailinglist Archive: opensuse (1470 mails)

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Re: [opensuse] Older install won't boot
On Fri, Feb 26, 2016 at 6:38 AM, Jim Flanagan <parttimelinux@xxxxxxxxx> wrote:
But, I really don't
follow the options of installing grub to different locations, MBR, primary,
extended, /. Is there a not too technical tutorial that explains this?


When you install GRUB in MBR, GRUB first stage code is written to the
first sector, disk address of second stage is computed and written to
MBR as well. BIOS loads GRUB boot code, boot code loads second stage
and jumps to it.

When you install GRUB anywhere else, different first stage code is
written in MBR (or MBR is not touched at all if you clear
corresponding check box). This code scans partition table, finds
active partition, loads first sector from this partition and jumps to
it.

Traditional MBR code used by DOS or Windows will only scan primary
partition (note that extended partition is also primary). Syslinux MBR
code, used by current openSUSE when you tell it to write code to MBR
can also boot from logical partition (but I am not sure which tool can
be used to mark logical partition as active).

Installing GRUB to partition does *not* mean you will actually boot
from this partition (use installed GRUB) - you also must make
partition where GRUB is installed as active. Normally YaST does it for
you.

Is it non-technical enough?
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