My MBR seems to be ignored, windows 10 boots without loading syslinux

bmarques · 2016-02-04 17:22:58

Hi there!

To be totally honest, I've often had problems when trying to fix my grub or syslinux after installing a Windows aside an already existing linux.
But this time I am really stuck:

I tried all the techniques I knew of, and more with what I found on internet, without any success.

* My partitions are as follows:

sda: Data ext4
sdb1: Arch ext4 (only partition on sdb that has the boot flag on)
sdb2: linux swap
sdb3: Windows 10

* UEFI is disabled in the bios

* I tried with grub
mount /dev/sdb1 /mnt
pacstrap /mnt grub
arch-chroot /mnt
mkinitcpio -p linux
grub-install --no-floppy --recheck /dev/sdb

* I tried with syslinux
mount /dev/sdb1 /mnt
pacstrap /mnt sysllinux
arch-chroot /mnt
mkinitcpio -p linux
syslinux-install_update -iam

* I even erased my MBR using syslinux's manual installation guide I found here: https://wiki.archlinux.org/index.php/Sy … on_on_BIOS

dd bs=440 count=1 if=/usr/lib/syslinux/bios/mbr.bin of=/dev/sdb

but Nothing works out!

I don't know much about these very low-level things, but for what I understood, the bios directly loads the mbr (these 440bytes I just overwrote), which then tells the computer which partition to load no?
Since I completely erased my mbr and rewrote it with syslinux things, I just can't figure out why my laptop keeps booting on Windows 10, bypassing completely syslinux / grub

I've been ripping the hair off my skull all afternoon tryin to figure out what I missed.
I would LOVE that one of you could point a finger at how stupid I am, and show me what I did wrong
Thanks in advance for your help!!

Last edited by bmarques (2016-02-04 17:44:26)

nomorewindows · 2016-02-04 17:56:59

We all know you love Windows 10, come on admit it!
Fastboot maybe causing you some trouble, and you may need to disable it.
Are you sure it's not a GPT partition even though you aren't using UEFI?
You obviously are booting from the second hard drive.
What are the contents of grub and syslinux configuration files?

Head_on_a_Stick · 2016-02-04 21:28:47

Perhaps the Windows bootloader has ensconced itself on /dev/sda

What happens if you remove that drive?

Please post the output of:

# parted -l

This command can be run from any live ISO.

bmarques · 2016-02-05 08:59:59

Thanks for your replies,

I checked my syslinux.cfg and noticed that something went wrong with my home partition.
I focused on sdb since it was the only hard drive I did modifications on,
But actually, Windows totally ignored my ext4 partition on sda, and wrote a 500M bootsector right over my home disk... (as London suggested..)
What the hell? The installer doesn't even ask if it is OK to write on another disk like that.
Thank you for your help, I will try to fix this mess somehow.

nomorewindows · 2016-02-05 19:02:02

Time for testdisk/photorec...

alphaniner · 2016-02-05 19:09:40

I noticed in OP you wrote:

sda: Data ext4

Did you really format the entire disk (no partition table)? If so, I can't really blame Windows for borking it.

bmarques · 2016-02-09 13:34:47

Hi there,

Thanks, I finished setting things up back as they were supposed to be.
Concerning my sda, I didn't do anything to this disk. It had a partition (sda1) which was formerly my home on linux, and was in ext4.
During the windows install, I didn't do any modification on sda, that's why I didn't expect windows to write its bootloader on sda...
Anyway, as it is suggested, the best is still to install windows first, if a dual boot with windows is needed.
I have to work with some proprietary hardware (Epiphan frame grabbers) and they do not provide kernel modules for Arch. They do for ubuntu though so I should have dual booted with ubuntu instead of windows, would have been less troubles.. )

Anyway, that you all for your help!

Head_on_a_Stick · 2016-02-09 13:54:58

bmarques wrote:

Windows totally ignored my ext4 partition on sda, and wrote a 500M bootsector right over my home disk... (as London suggested..)
What the hell? The installer doesn't even ask if it is OK to write on another disk like that.

AFAIUI, the Windows bootloader needs to be on the "first" disk.

See https://www.gnu.org/software/grub/manua … 02fWindows

Arch Linux

#1 2016-02-04 17:22:58

My MBR seems to be ignored, windows 10 boots without loading syslinux

#2 2016-02-04 17:56:59

Re: My MBR seems to be ignored, windows 10 boots without loading syslinux

#3 2016-02-04 21:28:47

Re: My MBR seems to be ignored, windows 10 boots without loading syslinux

#4 2016-02-05 08:59:59

Re: My MBR seems to be ignored, windows 10 boots without loading syslinux

#5 2016-02-05 19:02:02

Re: My MBR seems to be ignored, windows 10 boots without loading syslinux

#6 2016-02-05 19:09:40

Re: My MBR seems to be ignored, windows 10 boots without loading syslinux

#7 2016-02-09 13:34:47

Re: My MBR seems to be ignored, windows 10 boots without loading syslinux

#8 2016-02-09 13:54:58

Re: My MBR seems to be ignored, windows 10 boots without loading syslinux

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