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Old 08-12-2019, 05:29 PM   #1
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Registered: Mar 2018
Distribution: Slackware-14.2-current
Posts: 5

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[SOLVED] Dualboot Slackware and FreeBSD on separate drives with grub2 - FreeBSD overrides grub

Hello fellow Slackers,
I want to dualboot Slackware and FreeBSD (I know, I know) using grub2. The OS are on different drives. I installed Slackware and grub, and edited 40_custom with my FreeBSD parameters, then grub-mkconfig -o /boot/grub.grub.cfg. Next I installed FreeBSD 12.0 on a second HD. When I boot I get the FreeBSD bootmanager; it has somehow overwritten or overridden the grub bootloader. When I uninstall FreeBSD the grub menu appears on reboot. do I bypass FreeBSD's bootloader and use grub instead? Did my FreeBSD install over-write the MBR? (sorry forgot to mention I have older hardware and can only use MBR and no GPT; also UFS on FreeBSD). It must not have since I get grub back when I uninstall FreeBSD. There was no option to install FreeBSD without a bootloader. I know I've gotten this to work successfully in the past but can't remember what I did. What am I missing? Can I somehow delete the FreeBSD bootloader? I did quite a bit of searching but couldn't find where people had installed the OSs on separate drives. Thank you! Jim

Last edited by Indyman; 08-13-2019 at 04:37 PM. Reason: marking as solved
Old 08-12-2019, 09:02 PM   #2
Registered: Oct 2010
Location: Ontario, Canada
Distribution: Slackware, Manjaro (for gaming)
Posts: 104

Rep: Reputation: 88
If you can't boot into Slackware, boot with a slackware DVD and jump start your system using it as your boot loader. e.g. it tells you what to do right above the prompt when you boot with one:

huge.s root=/dev/sd?? noinitrd

Then simply reinstate grub again in the MBR.

grub-install /dev/sda

or whatever your boot device is.

P.S. When booting FreeBSD from lilo or grub I used to just chainload it like a Windows partition so that should work if you've already set that up in grub.cfg, after putting grub's MBR component back.

Last edited by TheRealGrogan; 08-12-2019 at 09:07 PM.
Old 08-13-2019, 12:17 AM   #3
Didier Spaier
LQ Addict
Registered: Nov 2008
Location: Paris, France
Distribution: Slint64- on Lenovo Thinkpad W520
Posts: 8,917

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Probably your BIOS is set up to try to boot first off the drive where FreeBSD is installed and only if that fails on the drive where Slackware is installed. This can usually be changed from the BIOS setup menu.

Last edited by Didier Spaier; 08-13-2019 at 09:43 AM.
Old 08-13-2019, 08:43 AM   #4
Senior Member
Registered: Jan 2008
Location: florida panhandle
Distribution: slackware64-current, arch, ubuntu, others
Posts: 3,266

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I second check you bios to see if you can change the boot order. If that isn't possible for what ever reason maybe open the case and swap the cables on the drives.
Old 08-13-2019, 04:33 PM   #5
LQ Newbie
Registered: Mar 2018
Distribution: Slackware-14.2-current
Posts: 5

Original Poster
Rep: Reputation: Disabled
Thanks Everyone,
Turns out it was the boot order in the BIOS(!) Once I changed the boot order to have the Slackware disk boot first, it booted into grub and I was also able to access my
FreeBSD system. The fact that when I removed FreeBSD that the machine booted from grub on the Slackware disk should have indicated to me that the MBR had not been overwritten (good idea though TheRealGrogan). I'm marking this one solved. Thanks again - LQ rocks!!

Last edited by Indyman; 08-13-2019 at 04:35 PM.


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