[syslinux] [PATCH] : Adding dlabel option to chain.c32

Ady Ady ady-sf at hotmail.com
Fri Jul 15 08:53:53 PDT 2016


> On 30.06.2016 19:41, Erwan Velu via Syslinux wrote:
> > The exisiting label= option offer to boot on a gpt partition that have
> > a particular label.
> > The existing guuid= option offer to boot on a disk or partition with a
> > particular label.
> > 
> > This new option offer to boot the disk that have a partition which
> > have a given label.
> > The label is so just a way to detect a disk to boot.
> > 
> > A typical use is for making an intelligent localboot like :
> > 
> >     label localboot
> >         com32 chain.c32
> >         append dlabel=datapartition
> > 
> > This allow booting on a disk that sports a least one partition
> > labelled "datapartition".
> > 
> > You can consider dlabel= doing almost what mbr= does but by inspecting
> > the gpt partitions label.
> > 
> > 
> > Please find below the commit :
> > https://github.com/ErwanAliasr1/syslinux/commit/ebf8cbfb8cef49517aa36b4a79998b4332289489
> > 
> 
> 
> # gdisk -l /dev/vda
> ...
> Partition table scan:
>   MBR: protective
>   BSD: not present
>   APM: not present
>   GPT: present
> 
> Found valid GPT with protective MBR; using GPT.
> ...
> Number  Start (sector)    End (sector)  Size       Code  Name
>    1            2048          411647   200.0 MiB   EF00  EFI System Partition
>    2          411648         1435647   500.0 MiB   8300  BOOT System Partition
>    3         1435648        22646783   10.1 GiB    8300  ROOT System Partition
>    4        22646784        25163775   1.2 GiB     8200  SWAP System Partition
> 
> 
> # fdisk -l /dev/vda
> ...
> Disklabel type: gpt
> ...
> Device        Start      End  Sectors  Size Type
> /dev/vda1      2048   411647   409600  200M EFI System
> /dev/vda2    411648  1435647  1024000  500M Linux filesystem
> /dev/vda3   1435648 22646783 21211136 10.1G Linux filesystem
> /dev/vda4  22646784 25163775  2516992  1.2G Linux swap
> 
> 
> # fatlabel /dev/vda1 
> labelefi   
> 
> # e2label /dev/vda2
> labelboot
> 
> # e2label /dev/vda3
> labelroot
> 
> # swaplabel /dev/vda4
> LABEL: labelswap
> ...
> 
> 
> Filesystem *label* and *label* of a swap area
> distinguish from
> GPT *name* of a partition
> 
 
 
_If_ I understand Erwan's patch correctly, we are talking about the GPT Partition Name, not the 
filesystem's label (but I could be wrong).
 
 
> 
> Therefore -if- you are referring to a GPT partition *name*,
> simple *name* as append option - for GPT partition *name* selection, should suffice
> i.e.
>   ...
>   append name=gptpartitionname
 
 
Not exactly. We are distinguishing between the GPT Partition Name being used just to select the 
next device (for example, your "ROOT System Partition"), and the (Protective) MBR we are jumping 
to, in BIOS / CSM mode.

In my prior email I suggested "diskbypartname" with relevant explanations (see 
http://www.syslinux.org/archives/2016-July/025305.html ).

Tests and feedback are appreciated.

Regards,
Ady.

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