Failing to Multiboot OpenBSD - stuck at partitions and Linux GRUB

Question

I am trying my hand at learning multibooting, so far my target PC has Antix-Linux ext4 on one partition, FreeBSD UFS on another, ExFat common data on a 3rd, Target PC has been partitioned with GPARTED and GPT partitioning scheme as under:

My PC has BIOS not UEFI.

 /dev/sda1 - 1 GB - fat32 - flags - boot, esp
 /dev/sda2 - 3 GB - flags - linux-swap
 /dev/sda3 - 15 GB - ext4 - Antix_Linux
 /dev/sda4 - 250 GB - exfat
 /dev/sda5 - 15 GB - freebsd_UFS
 /dev/sda6 - 0.5 GB - openbsd boot (formerly type 'EF' now type '0D')
 /dev/sda7 - rest space 15 GB -openbsd 'A6' type UFS

1] OpenBSD with Ventoy - installed from the install77.iso file, downloaded filesets from http since it did not read from cd0 or disk, got stuck at installboot. Then it was showing error EFI device busy, and since I don't have EFI, I changed the /dev/sda6from type EF to 0D(boot bios) and installboot successfully completed.

Then I rebooted, and trying to add a menuentry in 40_custom grub file in Antix-Linux, whose grub boots the system, but update-grub is showing warning discarded incorrectly nested partition hostdisk/dev/sda,gpt7,bsd(1-14)

May you please extend your help in these cases. Regards.

• oldfred: All installs have to be in same boot mode UEFI or BIOS. Or you have to directly boot from one time UEFI boot menu. Once you start to boot, you cannot change, or grub can only boot other installs in same boot mode.
• Spandan: @oldfred I have not consciously chosen UEFI anywhere, I have kept the /dev/sda1 to install rEFInd later, following people reviews, but I have doubt about the /dev/sda6 which I was forced to create by OpenBSD installer. Cant OpenBSD operate from a single partition like Linux and FreeBSD?
• oldfred: Do not know OpenBSD, but rEFInd only works for UEFI installs. rodsbooks.com/efi-bootloaders Alternative efi boot manager for UEFI limited systems: rodsbooks.com/refind I have used rEFInd for emgency boot on my PC.

Answer 1

The section below titled "My Way of Installing the Triple Boot" describes the steps for installing which avoids the warning message posted in your question. Basically, Grub is updated before the partition causing the warning message is created.

In both your question and posted answer, you are trying to install a BIOS booting OpenBSD to a GPT drive. This results in the OpenBSD installer terminating before completing the installation. My answer avoids this by hybrid partitioning the drive before installing OpenBSD. Afterwards the hybrid partitioning can be left in place or removed.

Note
Before answering this question, I assumed only Windows could be installed to BIOS boot on a hybrid partitioned drive. OpenBSD can BIOS boot on MBR partition table, GPT and hybrid partitioned drives.

When updating grub after installing OpenBSD, The following message appears multiple times where X is positive integer. This is a warning message which can be ignored.

warning: Discarding improperly nested partition (hostdisk//dev/sda,gpt5,bsdX).

Below are two Bash scripts that can be used to keep this message from appearing.

• The following script filters out the warning message.

  #!/usr/bin/bash
  /usr/sbin/update-grub |& grep -v "warning: Discarding improperly nested partition (hostdisk//dev/sda,gpt5,bsd"
  

• The following script temporarily sets the offending partition type to zero.

  #!/usr/bin/bash
  if [[ "$USER" != root ]]; then
   echo "0ドル: You must run this as root"
   exit 1
  fi
  DEVICE=/dev/sda
  PARTITION=5
  TYPE="$(sfdisk --part-type $DEVICE $PARTITION)"
  TYPE00=00000000-0000-0000-0000-000000000000
  TYPEA6=824CC7A0-36A8-11E3-890A-952519AD3F61
  if [[ "$TYPE" == "$TYPEA6" ]] then
   sfdisk --no-tell-kernel --part-type $DEVICE $PARTITION "$TYPE00"
   partprobe
  fi
  /usr/sbin/update-grub
  STATUS=$?
  if [[ "$TYPE" == "$TYPEA6" ]] then
   sfdisk --no-tell-kernel --part-type $DEVICE $PARTITION "$TYPEA6"
   partprobe
  fi
  exit $STATUS
  

The scripts should be stored in the /usr/local/sbin folder under the name update-grub. The owner:group should be root:root and the mode bits should be set to 0755. In other words, enter the commands below as the root user.

 chown root:root /usr/local/sbin/update-grub
 chmod 0755 /usr/local/sbin/update-grub

---

My Way of Installing the Triple Boot

Below are the instructions for installing a AnitX Linux, FreeBSD and OpenBSD triple boot on a SATA drive. The operating system need to be installed in the order given.

AntiX Linux

1. Boot from the AntiX Linux installation media. When an image similar to the one below appears, select "Use Modern Kernel".

   Use Modern Kernel

2. When the desktop appears, open a Terminal Application window. Enter the following command be become the root user. You will need to enter the rest of the commands as the root user. Note: The password was demo.

   sudo -s
   

3. Enter the command below to create a GPT and add the following partitions: BIOS boot partition, Linux filesystem and Microsoft basic data.

   gdisk /dev/sda
   

   The gdisk command is interactive. Enter the values in the first column of the table given below. Note: The commands are case independent.

   Entry	Default	Type	Comment
   o	command	Create a new empty GUID partition table (GPT).
   y	parameter	Do you want to proceed?
   n	command	Add a new partition.
   1	✅	parameter	Partition number.
   2048	✅	parameter	First sector.
   +1m	parameter	Set partition size 1 MiB.
   ef02	parameter	Hex code for BIOS boot partition.
   n	command	Add a new partition.
   2	✅	parameter	Partition number.
   4096	✅	parameter	First sector.
   +18g	parameter	Set partition size 18 GiB.
   8300	✅	parameter	Hex code for Linux filesystem.
   n	command	Add a new partition.
   3	✅	parameter	Partition number.
   37752832	✅	parameter	First sector.
   +235g	parameter	Set partition size 235 GiB.
   700	parameter	Hex code for Microsoft basic data.
   p	command	Print the GPT.
   w	command	Write tables to disk and exit.
   y	parameter	Do you want to proceed?

4. Enter the command below to format the third partition exFAT.

   mkfs.exfat -L MyShared /dev/sda3
   

5. Close the Terminal application and open the Installer application. Proceed with the installation of AntiX Linux.

   When an image similar to the one below appears, set "Use For" as shown below.

   Choose partitions

   When an image similar to the one below appears, confirm the actions are the same before continuing.

   Confirm actions

   When an image similar to the one below appears, change the size of the swap file if desired. When finished, select the "Next' button.

   Grub and swap

   Proceed with the installation until completion.

FreeBSD

1. Boot to AntiX Linux and open a Terminal Application window. Enter the following command be become the root user. You will need to enter the rest of the commands as the root user.

   sudo -s
   

2. As the root user, append the following to the end of the /etc/grub.d/40_custom file.

   menuentry "FreeBSD" {
    set root=hd0,gpt4
    kfreebsd /boot/loader
   }
   

   Enter the command below to update Grub.

   update-grub
   

3. Boot from the FreeBSD installation media. When you see a image similar to below, select Install.

   Install

   Proceed with the installation. When you see a image similar to below, select Manual, the OK.

   Manual

   When you see a image similar to below, select Create.

   Create

   In the Add Partition popup shown below, set the size to 18GB, the mountpoint to / and the label to FreeBSD UFS, then select OK.

   Add partition

   In the Boot Partition popup shown below, select No.

   Boot Partition

   When you see a image similar to below, select Finish.

   Finish

   In the Confirmation popup shown below, select Commit.

   Confirmation

   Proceed with the installation.

   Note
   When adding users, there will be the following question. Invite <new user> into other groups? []: If you want the su command to work for the new user, then enter the group wheel.

4. After you have finished installing and have booted to the FreeBSD installation, enter the following commands as the root user. This will create a 3 GiB swap file.

   dd if=/dev/zero of=/usr/swap0 bs=1M count=3072 status=progress
   chmod 0600 /usr/swap0
   

   Append the following line to the end of /etc/fstab. I did this by using the nano text edtior. To install this editor, enter the command pkg install nano.

   md99 none swap sw,file=/usr/swap0,late 0 0
   

   Swap space will be added on system startup. To add swap space immediately, enter the following command.

   swapon -aL
   

5. Enter the following command to install software that will allow mounting of exFAT volumes.

   pkg install fusefs-exfat
   

   To get the software to execute at starup, append the following line to the end of /boot/loader.conf.

   fusefs_load="YES"
   

   Enter the following command to create the directory where the exFAT volume will be mounted.

   mkdir -p /media/MyShared
   

   Append the following line to the end of /etc/fstab.

   /dev/ada0p3 /media/MyShared exfat rw,mountprog=/usr/local/sbin/mount.exfat 0 0
   

   The exFAT volume will be mounted on system startup. To mount immediately, enter the following commands.

   kldload fusefs
   mount -a
   

OpenBSD

1. Boot to AntiX Linux and open a Terminal Application window. Enter the following command be become the root user. You will need to enter the rest of the commands as the root user.

   sudo -s
   

2. As the root user, append the following to the end of the /etc/grub.d/40_custom file.

   menuentry "OpenBSD" {
    set root=hd0,gpt5
    kopenbsd -r sd0a /bsd
   }
   

   Enter the command below to update Grub.

   update-grub
   

3. Enter the command below to add a OpenBSD disklabel partition.

   gdisk /dev/sda
   

   Note
   With a GPT partitioned disk, the installer will attempt to install an UEFI booting OpenBSD. To cause a BIOS booting installation, the gdisk command will be used to hybrid partition the drive. This will cause the installer to see the drive as only having a legacy MBR partition table.

   The gdisk command is interactive. Enter the values in the first column of the table given below. Note: The commands are case independent.

   Entry	Default	Type	Comment
   n	command	Add a new partition.
   5	✅	parameter	Partition number.
   568332288	✅	parameter	First sector.
   621803519	✅	parameter	Last sector.
   a600	parameter	Hex code for OpenBSD disklabel.
   p	command	Print the GPT.
   r	command	Switch to recovery and transformation options menu.
   h	command	Make hybrid MBR.
   3 4 5	parameter	GPT partition numbers.
   y	parameter	Place EFI GPT (0xEE) partition first in MBR?
   07	✅	parameter	Hex code for 2nd primary MBR partition.
   n	parameter	Set boot flag for 2nd primary MBR partition?
   da	parameter	Hex code for 3rd primary MBR partition.
   n	parameter	Set boot flag for 3rd primary MBR partition?
   a6	✅	parameter	Hex code for 4th primary MBR partition.
   y	parameter	Set boot flag for 4th primary MBR partition?
   o	command	Print the MBR partition table.
   w	command	Write tables to disk and exit.
   y	parameter	Do you want to proceed?

4. Boot from the OpenBSD installation media. When you see text similar to below, enter i followed by the Enter key.

   Welcome to the OpenBSD/amd64 7.7 installation program.
   (I)nstall, (U)pgrade, (A)autoinstall or (S)hell?
   

   When you see text similar to below, select the default OpenBSD by pressing the Enter key.

   Use (W)hole disk MBR, whole disk (G)PT, (O)penBSD area or (E)dit? [OpenBSD]
   

   When you see text similar to below, select the default a by pressing the Enter key.

   Use (A)uto layout, (E)dit auto layout, or create (C)ustom layout? [a]
   

   If you see text similar to below, enter yes followed by the Enter key.

   Directory does not contain SHA256.sig. Continue without verification? [no]
   

5. After you have finished installing and have booted to the OpenBSD installation, enter the following commands as the root user. This will install the software needed to mount the exFAT volume.

   pkg_add exfat-fuse
   mkdir -p /media/MyShared
   

   To mount the exFAT volume, enter the following commands.

   disklabel -pm sd0
   mount.exfat /dev/sd0i /media/MyShared
   

6. Remove the hybrid partitioning.

   Note
   This step is optional.

   Boot to AntiX Linux and open a Terminal Application window. Enter the command below to remove the hybrid partitioning.

   sudo gdisk /dev/sda
   

   The gdisk command is interactive. Enter the values in the first column of the table given below. Note: The commands are case independent.

   Entry	Default	Type	Comment
   x	command	Switch to extra functionality options menu.
   n	command	Create a new protective MBR.
   o	command	Print the MBR partition table.
   w	command	Write the MBR partition table to disk and exit.
   y	parameter	Do you want to proceed?

---

Downloaded Installation ISO Files

• AntiX Linux: antiX-23.2_x64-full.iso
• FreeBSD: FreeBSD-14.2-Release-amd64-dvd1.iso
• OpenBSD: install77.iso

---

References

• mount.exfat-fuse
• doas

Below are specific to AntiX Linux.

• GRUB/Chainloading
• Check GRUB_DISABLE_OS_PROBER

Below are specific to FreeBSD.

• How to format an USB drive on FreeBSD
• 12.12. Adding Swap Space
• How To Add Swap on FreeBSD Unix Systems
• Booting FreeBSD via GRUB
• gpart
• fstab
• How to mount exFAT formatted SD memory card on FreeBSD.

Below are specific to OpenBSD.

• disklabel
• doas.conf
• Double boot OpenBSD: GPT disk, not chainload
• OpenBSD FAQ - Package Management
• Mount exFAT file system on OpenBSD

Answer 2

Finally, I found a solution, ignore the installer asking to create 2 partitions of EF and A6, just make one A6 partition, let disklabel create auto-layout and reboot.

Add a menu-entry in 40_custom file of /etc/grub.d as follows:

menuentry "OpenBSD 7.7" {
 kopenbsd -r sd0a (hd0,gpt6)/bsd
}

• Community: Your answer could be improved with additional supporting information. Please edit to add further details, such as citations or documentation, so that others can confirm that your answer is correct. You can find more information on how to write good answers in the help center.
• David Anderson: Does this answer solve the problem of update-grub is showing warning discarded incorrectly nested partition hostdisk/dev/sda,gpt7,bsd(1-14)?
• Spandan: @DavidAnderson - No, that still shows, but upon further reading, I found out that Grub complains and rEFInd is recommended. But for now my install and boot of OpenBSD is happening.
• David Anderson: The rEFInd Boot Manager only works with (U)EFI booting. Notice I stated "BOOT MANAGER". It is not a boot loader. The rEFInd Boot Manager instructs the boot manager built into the (U)EFI firmware as to what to boot next. BIOS firmware has no way to do this. On the other hand, GRUB is a boot loader. GRUB is the acronym for Grand Unified Bootloader. Once you have booted to GRUB, you can use GRUB to boot other operating systems. GRUB can be installed to BIOS or (U)EFI boot.