Syslinux - Jan 2014 - syslinux and btrfs-formatted dos/MBR partition

Hello syslinux list,

I have installed Arch over a btrfs-formatted dos/MBR primary
partition* (no btrfs subvolumes, just installing everything including
/boot in the root of the btrfs).

I have been unsuccessful for several days trying to get it to boot
with syslinux (6.02-8 package from Arch, also tried 4.07-1  Arch
package). All I am getting is the copyright header line and a blinking
cursor without keyboard control (can't type). No boot: prompt, no
menu, no response to CTRL-ALT-DEL (have to power off to reboot).

I am following the steps in Arch's beginner wiki and their syslinux
page (tried both the script provided by Arch and the manual method).
When I do this over ext4, everything works as expected, the copyright
line appears briefly then the menu pops up. No go with btrfs no matter
what I tried. So either it's a bug, or maybe I am repeatedly missing a
step?

It looks to me like the ldlinux.sys code embedded in the first 64k of
the btrfs partition crashes but no error message is generated. I have dd-ed
the first 64k of the btrfs partition and compared the file in a hex
editor with the ldlinux.sys file from an ext4 installation, and while
no exactly identical it seems to me that ldlinux.sys gets correctly
embedded as expected and does not overflow beyond the first 64k.

Any insight would be appreciated. I have been advised to talk to
Raphael_sc on irc about it, but I haven't managed to get a hold of him
so far.

* I am not using gpt because I want dual boot with winXP.

On Tue, Jan 21, 2014 at 2:53 AM, David de Marneffe
<daviddemarneffe at gmail.com> wrote:
> Hello syslinux list,
>
> I have installed Arch over a btrfs-formatted dos/MBR primary
> partition* (no btrfs subvolumes, just installing everything including
> /boot in the root of the btrfs).
>
> I have been unsuccessful for several days trying to get it to boot
> with syslinux (6.02-8 package from Arch, also tried 4.07-1  Arch
> package). All I am getting is the copyright header line and a blinking
> cursor without keyboard control (can't type). No boot: prompt, no
> menu, no response to CTRL-ALT-DEL (have to power off to reboot).
So BIOS-mode boot.  If your config wants a menu (likely "UI menu.c32"
or the like), you will never see a prompt unless it fails to load.
> I am following the steps in Arch's beginner wiki and their syslinux
> page (tried both the script provided by Arch and the manual method).
> When I do this over ext4, everything works as expected, the copyright
> line appears briefly then the menu pops up. No go with btrfs no matter
> what I tried. So either it's a bug, or maybe I am repeatedly missing a
> step?
What 3-4 letter sequence do you see that indicates its disk access
mode?  It should be CHS or EDD.
> It looks to me like the ldlinux.sys code embedded in the first 64k of
> the btrfs partition crashes but no error message is generated. I have dd-ed
> the first 64k of the btrfs partition and compared the file in a hex
> editor with the ldlinux.sys file from an ext4 installation, and while
> no exactly identical it seems to me that ldlinux.sys gets correctly
> embedded as expected and does not overflow beyond the first 64k.
It won't be identical as the chunks are in differing volume offsets
and as a result the map and checksum differ.

How big is this disk?  Where is the beginning address?  Are you
installing a new MBR?  Are you doing any other steps outside those on
the wiki?
> Any insight would be appreciated. I have been advised to talk to
> Raphael_sc on irc about it, but I haven't managed to get a hold of him
> so far.
The only person I recall getting that advice was attempting to
chainload from Windows to a btrfs volume.
> * I am not using gpt because I want dual boot with winXP.
This should be OK as long as you're under the 2TiB limit on total disk
size and your BIOS cooperates.

-- 
-Gene

Hello Gene, thanks for your reply.

Yes BIOS mode. The config wants a menu, which loads fine under ext4
and not under btrfs. Under btrfs I have also tried to remove the
syslinux.cfg file altogether (which should trigger the boot: prompt if
I am not mistaken) and the result is the same: only the copyright line
appears and no prompt.

The three letter sequence is EDD.

The disk is 160GB, here is the fdisk. Tried to install on /dev/sda6
and /dev/sda3.

Disk /dev/sda: 160.0 GB, 160041885696 bytes
255 heads, 63 sectors/track, 19457 cylinders, total 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
Disk identifier: 0x92e4538c

   Device Boot      Start         End      Blocks   Id  System
/dev/sda1              63   167750729    83875333+   7  HPFS/NTFS/exFAT
/dev/sda2       167750791   296093695    64171452+   f  W95 Ext'd (LBA)
/dev/sda3   *   296094015   312496379     8201182+  83  Linux
/dev/sda4       312496380   312576704       40162+  ef  EFI (FAT-12/16/32)
/dev/sda5       167750793   259915634    46082421    7  HPFS/NTFS/exFAT
/dev/sda6       259917824   296093695    18087936   83  Linux

It's true I am normally chainloading my Linux installations from the
WinXP bootloader, and that is what I initially tried with my btrfs
attempts, however in the course of testing I just backed up my MBR and
let syslinux overwrite it (yes I did set the boot flag before
installing syslinux and overwriting the MBR). That didn't make any
difference.

I am not performing any extra steps (although I tried adding hooks etc
but it didn't work). Simply put, if I follow the Arch wiki step by
step and format with ext4, everything works as expected. If I do the
same with btrfs, it's a no-no.

On 21/01/2014, Gene Cumm <gene.cumm at gmail.com>
wrote:
> On Tue, Jan 21, 2014 at 2:53 AM, David de Marneffe
> <daviddemarneffe at gmail.com> wrote:
>> Hello syslinux list,
>>
>> I have installed Arch over a btrfs-formatted dos/MBR primary
>> partition* (no btrfs subvolumes, just installing everything including
>> /boot in the root of the btrfs).
>>
>> I have been unsuccessful for several days trying to get it to boot
>> with syslinux (6.02-8 package from Arch, also tried 4.07-1  Arch
>> package). All I am getting is the copyright header line and a blinking
>> cursor without keyboard control (can't type). No boot: prompt, no
>> menu, no response to CTRL-ALT-DEL (have to power off to reboot).
>
> So BIOS-mode boot.  If your config wants a menu (likely "UI
menu.c32"
> or the like), you will never see a prompt unless it fails to load.
>
>> I am following the steps in Arch's beginner wiki and their syslinux
>> page (tried both the script provided by Arch and the manual method).
>> When I do this over ext4, everything works as expected, the copyright
>> line appears briefly then the menu pops up. No go with btrfs no matter
>> what I tried. So either it's a bug, or maybe I am repeatedly
missing a
>> step?
>
> What 3-4 letter sequence do you see that indicates its disk access
> mode?  It should be CHS or EDD.
>
>> It looks to me like the ldlinux.sys code embedded in the first 64k of
>> the btrfs partition crashes but no error message is generated. I have
>> dd-ed
>> the first 64k of the btrfs partition and compared the file in a hex
>> editor with the ldlinux.sys file from an ext4 installation, and while
>> no exactly identical it seems to me that ldlinux.sys gets correctly
>> embedded as expected and does not overflow beyond the first 64k.
>
> It won't be identical as the chunks are in differing volume offsets
> and as a result the map and checksum differ.
>
> How big is this disk?  Where is the beginning address?  Are you
> installing a new MBR?  Are you doing any other steps outside those on
> the wiki?
>
>> Any insight would be appreciated. I have been advised to talk to
>> Raphael_sc on irc about it, but I haven't managed to get a hold of
him
>> so far.
>
> The only person I recall getting that advice was attempting to
> chainload from Windows to a btrfs volume.
>
>> * I am not using gpt because I want dual boot with winXP.
>
> This should be OK as long as you're under the 2TiB limit on total disk
> size and your BIOS cooperates.
>
> --
> -Gene
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