MultiBoot OpenBSD/Debian

[Funkygoby]

Hello there!

Long description, then problem, then question.

Description:
My main OS is Debian oldstable for now on my main laptop and I used to teach myself OpenBSD with a spare dedicated latptop.
This second laptop as been lend to a friend who was in distress since here macbook had died.

Now, this laptop is back in my house and I can resume my learning.
I was planning to install Debian jessie for android dev and OpenBSD on his disk.

-First I installed Debian. I partitionned the disk like that:
sda1 50GB empty (for OBSD)
sda2 50GB for debian separated in 3 logicals partitions (/,swap and /home)
Installation went smoothly as I am seasonned with debian installation.

-Then, I proceed with OBSD installation (not my first time either but still newbie).
I may not remember exactly what I did but I am pretty sure I choose (e)dit at the partition step, didn't see the layout I was expecting (2 primary partitions), tried to build some layout anyway then cancelled.

At this point, I was expecting the layout to be still intact but I was wrong...

Problem:
On reboot, no os found. So I reinstalled debian 8 and I am waiting for more insight before retrying the OBSD install.

Question:
When does OpenBSD fdisk proceed? I though that any writing on disk wouldn't occur until I say so?

[shep]

I'm dualbooting Debian Testing with OpenBSD current on an i386 system.

I installed Debian with
/ = /dev/sda1
swap = /dev/sda2
/home = /dev/sda3

Leave space for OpenBSD on /dev/sda4

Use fdisk to label sda4 as an OpenBSD file system (Type A6). Then install OpenBSD into the OpenBSD partition. Do not use the whole disk!

Reboot to debian and add an OpenBSD chain loading command in /etc/grub.d. Run # update-grub

This is a rough overview - I can provide specifics if needed later.

[jggimi]

To answer one very specific question:

Originally Posted by Funkygoby

When does OpenBSD fdisk proceed? I though that any writing on disk wouldn't occur until I say so?

In command mode, "quit" will write your changes. You must use "exit". Excerpted from fdisk(8).

     exit    Exit the current level of fdisk, either returning to the
             previously selected in-memory copy of a MBR, or exiting the
             program if there is none.

     quit    Exit the current level of fdisk, either returning to the
             previously selected in-memory copy of a MBR, or exiting the
             program if there is none.  Unlike exit it does write the modified
             block out.

[scottro]

Shep's way works fine, I've used it frequently. I have a short page that goes into a bit more detail, but basically reiterates what was said in Shep's post.

https://srobb.net/openbsdmultiboot.html

[e1-531g]

I have Windows and OpenBSD dualboot and I use similar shep's way.
I use Grub-modern (Grub2) from Debian Jessie amd64 Live Standard image as bootloader. I don't have Debian installed and I haven't while installing OpenBSD and/or bootloader. Just booted from Live image and installed Grub2.
Grub2 is far less bloated than Windows boot menu program.

[hitest]

Originally Posted by shep

I'm dualbooting Debian Testing with OpenBSD current on an i386 system.

I installed Debian with
/ = /dev/sda1
swap = /dev/sda2
/home = /dev/sda3

Leave space for OpenBSD on /dev/sda4

Use fdisk to label sda4 as an OpenBSD file system (Type A6). Then install OpenBSD into the OpenBSD partition. Do not use the whole disk!

Reboot to debian and add an OpenBSD chain loading command in /etc/grub. Run # update-grub

This is a rough overview - I can provide specifics if needed later.

I run a similar set-up dual booting Slackware 14.2 and OpenBSD 5.9. The only difference is that I add the following at the end of /etc/lilo.conf

other = /dev/sda4
label = OpenBSD
table = /dev/sda

After editing /etc/lilo.conf I run # lilo -P fix and reboot. That will do it.

[Funkygoby]

Thanks all.

@jggimi:
So fsdisk is the same in the installer and in the base and as such, behave the same way. I'll be more careful when I reach the fdisk step.

@shep, scottro, e1-531g, hitest:
Ok, I will retry this after I format a primary part to OpenBSD type.
After the install a simple os-probe and grub-install will suffice under debian.

[hitest]

Originally Posted by shep

Reboot to debian and add an OpenBSD chain loading command in /etc/grub. Run # update-grub

This is a rough overview - I can provide specifics if needed later.

Hey shep, thanks for the overview! Can you please provide the chain loading command in /etc/grub? I am curious.

[shep]

Originally Posted by hitest

Hey shep, thanks for the overview! Can you please provide the chain loading command in /etc/grub? I am curious.

I used this guide. Also found in the mailing lists.

My /etc/grub.d/40_custom

#!/bin/sh
exec tail -n +3 $0
# This file provides an easy way to add custom menu entries.  Simply type the
# menu entries you want to add after this comment.  Be careful not to change
# the 'exec tail' line above.
menuentry "OpenBSD Current" {
        set root=(hd0,4)
        chainloader +1
}

[hitest]

Originally Posted by shep

My /etc/grub.d/40_custom

#!/bin/sh
exec tail -n +3 $0
# This file provides an easy way to add custom menu entries.  Simply type the
# menu entries you want to add after this comment.  Be careful not to change
# the 'exec tail' line above.
menuentry "OpenBSD Current" {
        set root=(hd0,4)
        chainloader +1
}

Thanks, shep.

[shep]

Originally Posted by Funkygoby

Thanks all.

@jggimi:
So fsdisk is the same in the installer and in the base and as such, behave the same way. I'll be more careful when I reach the fdisk step.

My understanding is that fdisk has some variations between linux distributions and BSD's

After installing Debian, I installed Debian's fdisk package and used it to label the /dev/sda4 partition as A6. You could probably drop to the command line and run OpenBSD fdisk during the OpenBSD install. I felt more comfortable editing partition tables in Debian's bootloader using Debian's fdisk.

[jggimi]

OpenBSD's fdisk was rewritten in 1997. Prior to that it used a port of NetBSD's fdisk.

[Nureo]

Well. Here I found a solution. For Debian, through Trisquel (based on Ubuntu: based on Debian). Both uses GRUB2 any way.

For what I heard (just opinions, they depends of hardware), is better to install OpenBSD in a first partition, and in the second a GNU system, if you want the dual boot. But is OK.

You have GNU on the first partition. Did you install OpenBSD in a second? Well, let's configure GRUB2 on Debian:

$ sudo nano /etc/grub.d/40_custom

Immediately downside of comments (with those "#") lines. Initial "..." are a “Tab”:

menuentry "OpenBSD" {
...set root=(hd0,1)
...chainloader +1
}

If you have OpenBSD on the first partition, this section: “...set root=(hd0,1)” stays like that. If it is not, just change, and put “...set root=(hd0,2)”. If you have troubles, please tell me here.

When you get it, just "Ctrl+X", "Y" (yes), and "Enter". Changes saved.

Like root:

# update-grub

And then...

# grub-mkconfig -o /boot/grub/grub.cfg

Almost done...

GRUB2 may ask you for a user to log into a Operative System partition. The user will be "grub", but you don't know the password (five numbers).

You can use the password, by knowing it, or you can delete it by editing a configuration text:

$ sudo nano /boot/grub/grub.cfg

When it says:

### BEGIN /etc/grub.d/01_PASSWORD ###
set superusers=grub
password grub FIVENUMBERS
### END /etc/grub.d/01_PASSWORD ###

If you don't want any more the password requirement, do this (comment this lines):

### BEGIN /etc/grub.d/01_PASSWORD ###
### set superusers=grub
### password grub FIVENUMBERS
### END /etc/grub.d/01_PASSWORD ###

"Ctrl+X", "Y" (yes), y "Enter". Changes saved.

NOTE: Do not try then "sudo update-grub" or "sudo update-grub2". If you do it the password may be reestablished.

Well. Reboot, and tell us how it goes!

[shep]

For what I heard (just opinions, they depends of hardware), is better to install OpenBSD in a first partition, and in the second a GNU system, if you want the dual boot. But is OK.

I've read that a number of factors need to be considered to optimize a partition layout.

The lower numbered partitions occupy a more peripheral, physical location on the disk - more disk area will pass the read/write head per revolution.

Using this rationale, I would put the OS that I intend to predominately utilize on the lower numbered, more peripheral partitions.

[girarde]

If platter surface speed is going to matter very much, either you have pretty old disks or your application is sufficiently time critical that you should rethink dual booting without adding a spindle for the second OS.

[bsd-keith]

From what I can remember, it used to be advised to put all BSDs first before Linux, because of a disk size limit for booting. or something, but that used to be about an 8GB limit, & I think that is no longer the case - but I would always put BSD before Linux.

[jggimi]

Originally Posted by bsd-keith

From what I can remember, it used to be advised to put all BSDs first before Linux, because of a disk size limit for booting...

On amd64 and i386, the OpenBSD two-stage bootloader uses BIOS services to load the kernel into memory. The kernel location on disk must be addressable by the BIOS. The specific limitation varies, depending on the individual BIOS implementation and the disk technology being used.

While no longer an issue with modern BIOS and disk drive technologies, one never really knew the address limit without actually testing it. As I recall, the limit could range from as little as 528MB upward into a wide variety of GB limits.

One of the benefits of having a small root directory was to avoid discovering the limit after updating or upgrading, and having a new kernel with sectors outside the BIOS addressing limit.

But with more modern hardware, this is much less of a concern and the "large drive" considerations that discussed the BIOS limit were removed from the FAQ.

[ocicat]

Originally Posted by bsd-keith

From what I can remember, it used to be advised to put all BSDs first before Linux, because of a disk size limit for booting. or something...

It is a BIOS limitation. One of the better explanations I have seen is at the following:

http://www.dewassoc.com/kbase/hard_d...e_barriers.htm

[hrsetrdr]

Originally Posted by shep

I'm dualbooting Debian Testing with OpenBSD current on an i386 system.

I installed Debian with
/ = /dev/sda1
swap = /dev/sda2
/home = /dev/sda3

Leave space for OpenBSD on /dev/sda4

Use fdisk to label sda4 as an OpenBSD file system (Type A6). Then install OpenBSD into the OpenBSD partition. Do not use the whole disk!

Reboot to debian and add an OpenBSD chain loading command in /etc/grub.d. Run # update-grub

This is a rough overview - I can provide specifics if needed later.

I am planning this very same type install, just wondering if this thread is still relevant for a Debian + OBSD 6.4?

[shep]

Originally Posted by hrsetrdr

I am planning this very same type install, just wondering if this thread is still relevant for a Debian + OBSD 6.4?

This is still relevant for MBR bootloaders. In the interim GPT/UEFI bootloading has become a newer option for supported hardware. I'm presently running Debian 10(Buster) and OpenBSD 6.4 with a GPT bootloader and this entry in Debian /etc/grub.d/40_custom

#!/bin/sh
exec tail -n +3 $0
# This file provides an easy way to add custom menu entries.  Simply type the
# menu entries you want to add after this comment.  Be careful not to change
# the 'exec tail' line above.
menuentry 'OpenBSD' {
         insmod part_gpt
         insmod search_fs_uuid
         insmod chain
         chainloader (hd0,gpt1)/BSD_BOOTX64.EFI
}

I renamed BOOTX64.EFI from OpenBSD to BSD_BOOTX64.EFI and copied it over to Debian /boot/efi/.

You can source BOOTX64.EFI from this howto:

https://blog.jasper.la/openbsd-uefi-...der-howto.html

Remember to create a new /boot/grub/grub.cfg file with the root command: update-grub.