[UEFI/GPT] [Dual-Boot] How to install FreeBSD (with ZFS) alongside another OS (sharing the same disk)

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patovm04

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Important notes:
1) This tutorial assumes you have the OS you want to dual-boot with already installed on your drive, and that you already have freed up some disk space. Essentially, you will be installing FreeBSD with root-on-ZFS on the remaining free space of the disk, instead of using the entire drive as it's done by default by FreeBSD's installer.
2) This method only works for GPT disk layouts using UEFI mode. Legacy BIOS and MBR disks are not supported. As always, make sure to disable Secure Boot and Fast Boot.
3) Here, we use ada0 (disk 1) for everything, and we assume your disk already has an EFI partition, located in partition 1 (ada0p1). Change it according to your setup, if needed. Run gpart show to be sure.
4) We will create our ZFS Pool with "Stripe" as the Virtual Device type (vdev).
5) After completing installation, to be able to choose what OS to boot you'll need to either install rEFInd boot manager, or use GRUB (assuming the other OS is a Linux distro). I personally recommend rEFInd, but I won't detail how to install it here. Neither will I explain how to alter the GRUB config. Just gonna show you how the respective entries should look like in each case.
6) Finally, I'm not responsible for any problem or data loss you may experience. This tutorial is not an unsafe procedure if you understand what you're doing (especially in regards to selecting the correct disk where you want to install). Anyway, do it at your own risk!


Well, let's start:
First of all, boot your FreeBSD install USB stick. Proceed installing as usual, until you reach the "Partitioning" stage. Here, choose the "Shell" option, so you can create your swap and ZFS partitions by hand:

# Load the ZFS kernel module:
kldload zfs

# Force 4K sectors:
sysctl vfs.zfs.min_auto_ashift=12

# Create a swap partition (in this case, of 4 GB size):
gpart add -a 4k -l swap0 -s 4G -t freebsd-swap ada0

# Create a ZFS partition to fill the remaining free space:
gpart add -a 4k -l zfs0 -t freebsd-zfs ada0

# Mount tmpfs in /mnt, where the installer will install the operating system to:
mount -t tmpfs tmpfs /mnt

# Create your zroot pool:
zpool create -f -o altroot=/mnt -O compress=lz4 -O atime=off -m none zroot /dev/gpt/zfs0

# Create ZFS file system hierarchy:
zfs create -o mountpoint=none zroot/ROOT
zfs create -o mountpoint=/ zroot/ROOT/default

# Define the default ZFS datasets for root zpool:
zfs create -o mountpoint=/tmp -o exec=on -o setuid=off zroot/tmp # We'll be using tmpfs for /tmp.
zfs create -o mountpoint=/usr -o canmount=off zroot/usr
zfs create zroot/usr/home
zfs create -o setuid=off zroot/usr/ports
zfs create zroot/usr/src
zfs create -o mountpoint=/var -o canmount=off zroot/var
zfs create -o exec=off -o setuid=off zroot/var/audit
zfs create -o exec=off -o setuid=off zroot/var/crash
zfs create -o exec=off -o setuid=off zroot/var/log
zfs create -o atime=on zroot/var/mail
zfs create -o setuid=off zroot/var/tmp

# Create a symlink to /usr/home:
ln -s /usr/home /mnt/home

# Change /tmp and /var/tmp permissions:
chmod 1777 /mnt/tmp # Not needed now.
chmod 1777 /mnt/var/tmp

# Configure the Boot Environment:
zpool set bootfs=zroot/ROOT/default zroot

# Instruct FreeBSD to mount ZFS pools during system initialization:
printf 'zfs_enable="YES"' >> /tmp/bsdinstall_etc/rc.conf

# Add an fstab entry to use a GELI-encrypted swap partition:
printf "/dev/gpt/swap0.eli\tnone\tswap\tsw\t0\t0\n" >> /tmp/bsdinstall_etc/fstab

# Add an fstab entry to use tmpfs for /tmp:
printf "tmpfs\t/tmp\ttmpfs\trw,mode=1777\t0\t0\n" >> /tmp/bsdinstall_etc/fstab

# Mount the existing EFI partition of your disk:
mount -t msdosfs /dev/ada0p1 /media

# Create FreeBSD boot directory in the EFI partition:
mkdir -p /media/efi/freebsd

# Copy FreeBSD loader to the previously created directory:
cp /boot/loader.efi /media/efi/freebsd/loader.efi

# Now add a UEFI boot entry:
efibootmgr --create --activate --label "FreeBSD" --loader "/media/efi/freebsd/loader.efi"

# Unmount EFI partition:
umount /media

# Exit Shell Partitioning mode, so bsdinstall can continue and complete the installation:
exit


After finishing the installation, don't forget to add a boot entry for FreeBSD in GRUB or rEFInd.
Here I share some sample entries to guide you a bit. Remember to modify them to reflect your own reality:

# For GRUB:
Code: 
menuentry "FreeBSD" {
    insmod part_gpt
    insmod fat
    set root=(hd0,gpt1)
    chainloader /efi/freebsd/loader.efi
}

# For rEFInd, add something like this at the end of refind.conf:
Code: 
# FreeBSD
menuentry "FreeBSD" {
    loader /efi/freebsd/loader.efi
    icon /efi/refind/icons/os_freebsd.png
}

That's all. Hope you find it useful!

Sources:
https://www.freebsd.org/doc/handbook/bsdinstall-partitioning.html
https://wiki.freebsd.org/RootOnZFS/GPTZFSBoot
http://kev009.com/wp/2016/07/freebsd-uefi-root-on-zfs-and-windows-dual-boot/
https://github.com/freebsd/freebsd-src/blob/releng/13.0/usr.sbin/bsdinstall/scripts/zfsboot
https://github.com/freebsd/freebsd-src/blob/releng/13.0/usr.sbin/bsdinstall/scripts/bootconfig


EDIT 1:
-Added some sources.

EDIT 2:
-Reworded the title for better clarity.
-Added a note about FreeBSD's efi loader name used in this tutorial.
-Removed /tmp from ZFS datasets, to use a tmpfs /tmp instead. This way it provides better performance and doesn't cause troubles with some programs, like Firefox on Wayland, for instance.

UPDATE (2021/02/12):
-Fixed some little issues.
-Added useful efibootmgr command.
-Updated FreeBSD efi boot loader name and location to match new FreeBSD 13.0 defaults.
-Added more sources.
 
Last edited:
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unwillexist

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Messages: 9

Just followed this guide but when i issue

mount -t zfs zroot/ROOT/default /mnt

it only says device is busy. What can i do ?
 
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amnixed

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patovm04 said:
Hello patovm04,
Click to expand...
I ran into a couple of problems following your guide:
patovm04 said:
# Instruct FreeBSD to mount ZFS pools during system initialization:
echo 'zfs_enable="YES"' >> /mnt/etc/rc.conf
Click to expand...
# echo 'zfs_enable="YES"' >> /mnt/etc/rc.conf
bash: /mnt/etc/rc.conf: No such file or directory

mkdir /mnt/etc or create zfs filesystem for /etc?

patovm04 said:
# Mount the existing EFI partition of your disk:
mount -t msdosfs /dev/ada0p1 /media
Click to expand...
gpart(8) says ada0p1 is the type ms-recovery (NTFS?) and mount(8) fails. Does the Windows 10 installer even have the option for FAT (=msdosfs?)?
 
twllnbrck

twllnbrck

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patovm04 said:
Essentially, you will be installing FreeBSD with root-on-ZFS on the remaining free space of the disk,
Click to expand...
Which advantage do you have to install FreeBSD with root on zfs when you dual boot from the same disk? Im just wondering ..
 
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patovm04

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twllnbrck said:
Which advantage do you have to install FreeBSD with root on zfs when you dual boot from the same disk? Im just wondering ..
Click to expand...
To be able to take advantage of ZFS most useful features such as boot environments, as far as I understand.
 
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patovm04

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amnixed said:
I ran into a couple of problems following your guide:

# echo 'zfs_enable="YES"' >> /mnt/etc/rc.conf
bash: /mnt/etc/rc.conf: No such file or directory

mkdir /mnt/etc or create zfs filesystem for /etc?


gpart(8) says ada0p1 is the type ms-recovery (NTFS?) and mount(8) fails. Does the Windows 10 installer even have the option for FAT (=msdosfs?)?
Click to expand...
Hmm it's difficult to help you if you're not following the steps to the letter (for instance, you are running bash which isn't even part of FreeBSD's live install media).
Also it's uncommon EFI not to be your first partition, but given that's your case, it's just a matter of figuring out the correct partition number (/dev/ada0p3 for example).
 
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amnixed

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patovm04 said:
Hmm it's difficult to help you if you're not following the steps to the letter (for instance, you are running bash which isn't even part of FreeBSD's live install media).
Also it's uncommon EFI not to be your first partition, but given that's your case, it's just a matter of figuring out the correct partition number (/dev/ada0p3 for example).
Click to expand...
You are right, I was probably inattentive following your guide (which is actually excellent), gave up too soon and proceeded with an MBR/UFS installation. Will try it again!
 
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313

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Thanks to the OP for the excellent tutorial. Following the instructions I was able to get dual boot going without any problems. I did however notice a couple of things that need correction, should one follow the steps by the letter.

1) The following is conflicting:

# Mount a tmpfs to /mnt, where the installer will install the operating system into:
mount -t tmpfs tmpfs /mnt
...
# Mount your pool:
mount -t zfs zroot/ROOT/default /mnt
Click to expand...

If tmpfs is mounted on /mnt, the latter mount command causes the 'device busy' error that some users noticed. The tmpfs mount command should be skipped.

2) This does not work as it is, because /mnt/etc does not exist:

# Instruct FreeBSD to mount ZFS pools during system initialization:
echo 'zfs_enable="YES"' >> /mnt/etc/rc.conf
Click to expand...

Instead, I did
echo 'zfs_enable="YES"' >> /tmp/bsdinstall_etc/rc.conf
..and the results were as expected.
 
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patovm04

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313 said:
Thanks to the OP for the excellent tutorial. Following the instructions I was able to get dual boot going without any problems. I did however notice a couple of things that need correction, should one follow the steps by the letter.

1) The following is conflicting:



If tmpfs is mounted on /mnt, the latter mount command causes the 'device busy' error that some users noticed. The tmpfs mount command should be skipped.

2) This does not work as it is, because /mnt/etc does not exist:



Instead, I did
echo 'zfs_enable="YES"' >> /tmp/bsdinstall_etc/rc.conf
..and the results were as expected.
Click to expand...
Hmm interesting 🤔, as I did follow it to the letter before posting it here and didn't have those issues. Maybe something's changed since then... If I recall correctly I used FreeBSD 12.1-RELEASE at the time.
Well, I guess the how-to needs some updating now. Gonna do it some time in the future after checking it thoroughly. Thank you
 
Zamana

Zamana

New Member


Messages: 19

Hi!

Can you tell me if your guide would work in the case of 2 separated HDDs?

On my laptop, I already have Windows 10 installed in the first HDD (for work), and I would like to install FreeBSD in the second HDD (for personal use).

Thanks.
 
drewlander

drewlander

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Thank you for the writeup! Well done!

Just for anyone else who runs into this:
I also ran into:
Bash: 
# echo 'zfs_enable="YES"' >> /mnt/etc/rc.conf
bash: /mnt/etc/rc.conf: No such file or directory
making the directory then re-running worked for me

After copying boot1.efi, I made a directory in EFI specifically for FreeBSD then ran:
Bash: 
 efibootmgr -c -l /mnt/EFI/FREEBSD/BOOTX64.EFI -L FREEBSD

working like a charm
 
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patovm04

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drewlander said:
Thank you for the writeup! Well done!

Just for anyone else who runs into this:
I also ran into:
Bash: 
# echo 'zfs_enable="YES"' >> /mnt/etc/rc.conf
bash: /mnt/etc/rc.conf: No such file or directory
making the directory then re-running worked for me

After copying boot1.efi, I made a directory in EFI specifically for FreeBSD then ran:
Bash: 
 efibootmgr -c -l /mnt/EFI/FREEBSD/BOOTX64.EFI -L FREEBSD

working like a charm
Click to expand...
Thanks, I just updated the guide. Those issues should be solved now :)
 
OP
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patovm04

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Zamana said:
Hi!

Can you tell me if your guide would work in the case of 2 separated HDDs?

On my laptop, I already have Windows 10 installed in the first HDD (for work), and I would like to install FreeBSD in the second HDD (for personal use).

Thanks.
Click to expand...
Not sure, I've never done it to be honest...
 
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scottro

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I just did this on FreeBSD-13.0-BETA2. I use CentOS-8-stream grub to boot it. (Though I had to lock grub at an earlier version as later versions weren't booting FreeBSD, though I had a different custom.cfg, as that was on a UFS partition).
Anyway, this time, got an error that it couldn't find the file, hit any key to continue, which I did, and it booted FreeBSD properly. So, anyway, thanks again, I think this is kind of neat to have a ZFS partition dual booting with Linux. It does, aside from giving people the chance to use bectl or beadm, also give them a chance to experience ZFS stability and such, though in laptop use, I don't know if it will be noticeable.
 
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