[syslinux] syslinux and btrfs-formatted dos/MBR partition

[David de Marneffe]

For the MBR: I usually don't touch the Microsoft MBR and chainload
Linux from the Microsoft bootloader. However while trying to get my
btrfs setup to work, I backed up the Microsoft MBR (dd if=/dev/sda
bs=440 count=1 of=MBRbackup.bin) and I installed the syslinux MBR. I
tried several ways:
- with the script provided by Arch: syslinux-install_update -i -a -m
- manual method with mbr.bin (first setting the boot flag on
/dev/sda3): dd if=/usr/lib/syslinux/bios/mbr.bin bs=440 count=1
of=/dev/sda
- manual method with altmbr.bin: printf '\x3' | cat
/usr/lib/syslinux/bios/altmbr.bin - | dd bs=440 count=1
iflag=fullblock conv=notrunc of=/dev/sda

No luck any way. Then I just restored the Microsoft MBR.

On 22/01/2014, Gene Cumm <gene.cumm at gmail.com> wrote:
> On Tue, Jan 21, 2014 at 7:42 AM, David de Marneffe
> <daviddemarneffe at gmail.com> wrote:
>> 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.
>
> Thanks.
>
>> 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.
>
> Which MBR?  How did you install it?  The common Microsoft one can not
> boot a non-primary partition but the Syslinux mbr.bin and altmbr.bin
> can.
>
> --
> -Gene
>
> A: Because it messes up the order in which people normally read text,
> especially the archives of mailing lists.
> Q: Why is Top-posting such a bad thing?
>
> "No one ever says, 'I can't read that ASCII(plain text) e-mail you sent
> me.'"
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