[syslinux] chain.c32 Insane primary (MBR) partition
Michal Soltys
soltys at ziu.info
Wed Jan 8 06:35:11 PST 2014
On 2014-01-03 08:07, Ady wrote:
> The following boot entries:
> #
> COM32 chain.c32
> APPEND fs ntldr=/bootmgr
> #
>
> or:
> #
> COM32 chain.c32
> APPEND hd0,1 ntldr=/bootmgr
> #
>
> might result in the following error:
>
> #
> Insane primary (MBR) partition.
> Can't find myself on the drive I booted from.
> #
The first line has been adjusted in later patches, but they are in
elflink and firmware branches only. Currently it would report:
Primary (MBR) with invalid offset and/or length.
This often happens if the disk/image is used on different computers
(e.g. on usb stick) and bios reports different disk sizes (usually +/- 1
sector). This is a bios bug (potentially nasty one, imagine GPT which
stores backup data at the end of the disk as well).
As current version of chain loader supports a good few potentially
dangerous operations - mostly related to fixing chs geometry to match
the one reported by bios - it's very strict at testing if everything is
OK before proceeding.
Current version also supports 'relax' option which turns off most sanity
checks, but it was added a good while after the v4 syslinuxes.
v4.05 works fine, as it was before merging new version of chain.
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