ZFS as Root Filesystem

Introduction

This wiki will show you how to install Funtoo on ZFS (rootfs).

Introduction to ZFS

For a quick tour of ZFS and have a big picture of its common operations you can consult the page ZFS Fun.

Prerequisites

   Important

ZFS designed for 64-bit systems. We only recommending and supporting 64-bit platforms and installations!

ZFS recommendation is to control entire disk, hence, guide reflecting only installing ZFS on whole disk and legacy boot. Installing on UEFI requires separate partition for /boot, formatted into FAT32 and not covered here, though, installation on UEFI is certainly possible. Guide also not describing anything related to encryption.

Downloading the ISO (With ZFS)

In order to install Funtoo on ZFS, you will need an environment such as live media with ZFS tools provided.

Creating a bootable USB from ISO (From a Linux Environment)

After you download the iso, you can do the following steps to create a bootable USB: TBA.

Creating ZFS partitions

We are letting ZFS automatically partition the drive. We use "partition" term, so it would be more familiar for many.

Creating of pool

root #  mkdir /mnt/funtoo
root #  zpool create -f -o ashift=12 -o cachefile=/tmp/zpool.cache -O normalization=formD -m none -R /mnt/funtoo -d -o feature@async_destroy=enabled -o feature@empty_bpobj=enabled -o feature@lz4_compress=enabled -o feature@spacemap_histogram=enabled -o feature@enabled_txg=enabled -o feature@extensible_dataset=enabled -o feature@bookmarks=enabled rpool /dev/sda

   Note

ashift 12 stands for 4-K block size sectors. Such type of hard drives are common nowadays.

Pool name is irrelevant, rpool used in this guide.

Create the zfs datasets

Create rootfs

root #  zfs create -o mountpoint=none rpool/ROOT
root #  zfs create -o mountpoint=/ rpool/ROOT/funtoo

Create optional datasets

Described below datasets are examples and optional. It's up to users to perform creation of their own datasets.

Home

root #  zfs create -o mountpoint=/home rpool/HOME
root #  zfs create -o mountpoint=/root rpool/HOME/root

Portage directories

root #  zfs create -o mountpoint=none -o setuid=off rpool/FUNTOO
root #  zfs create -o mountpoint=/usr/portage -o atime=off rpool/FUNTOO/portage
root #  zfs create -o mountpoint=/usr/portage/distfiles rpool/FUNTOO/distfiles

Build directory

root #  zfs create -o mountpoint=/var/tmp/portage -o compression=lz4 -o sync=disabled rpool/FUNTOO/build

Setting bootfs

When booting from ZFS, you must specify a boot device and a root file system within the pool that was identified by the boot device. By default, the dataset selected for booting is the one identified by the pool's bootfs property.

root # zpool set bootfs=rpool/ROOT/funtoo rpool

Installing Funtoo

Now that initial ZFS pool created, datasets ready, we can perform stage3 unpack and basic system installation. This part does not differ much from regular Funtoo Linux installation. http://www.funtoo.org/Install#Installing_the_Stage_3_tarball. We recommend using funtoo-current stages for ZFS.

root # cd /mnt/funtoo
root # wget http://build.funtoo.org/funtoo-current/x86-64bit/generic_64/stage3-latest.tar.xz

Extract the contents with the following command, substituting in the actual name of your stage 3 tarball (in case of arch optimized stage).

root # tar xpf stage3-latest.tar.xz

Now we need to create chroot environment by following:

root # cd /mnt/funtoo
root # mount -t proc none proc
root # mount --rbind /sys sys
root # mount --rbind /dev dev

Important step is to copy ZFS cache we created at the very beginning of our rpool creation into chroot.

root # mkdir -p /mnt/funtoo/etc/zfs
root # cp /tmp/zpool.cache /mnt/funtoo/etc/zfs/zpool.cache

You'll also want to copy over resolv.conf in order to have proper resolution of Internet hostnames from inside the chroot:

root # cp /etc/resolv.conf /mnt/funtoo/etc/

We are ready to chroot

root # chroot /mnt/funtoo /bin/bash
root # export PS1="(chroot) $PS1"; cd

Installing ZFS userspace and bootloader

Installing the ZFS userspace tools and kernel modules

In order to install ZFS packages we need to get portage tree first:

root # emerge --sync
root # emerge sys-fs/zfs

Installing GRUB 2

Install grub2:

root # echo "sys-boot/grub libzfs" >> /etc/portage/package.use
root # emerge grub

Initial kernel build

Funtoo stage3 have precompiled kernel but initramfs needs rebuilding to include ZFS binaries. This possible with --zfs argument:

root # genkernel initramfs --no-clean --no-mountboot --zfs

Configuring the Bootloader

sys-boot/grub require small partition, called Bios boot partition. We will use sgdisk, which is part of sys-apps/gptfdisk to create it.

root # sgdisk --new=2:48:2047 --typecode=2:EF02 --change-name=2:"BIOS boot partition" /dev/sda

After reboot

Create initial ZFS Snapshot

   Important

For a detailed overview, presentation of ZFS' capabilities, as well as usage examples, please refer to the ZFS Fun page.

Troubleshooting

Starting from scratch

If your installation has gotten screwed up for whatever reason and you need a fresh restart, you can do the following from sysresccd to start fresh:

Destroy the pool and any snapshots and datasets it has
root # zpool destroy -R -f tank

This deletes the files from /dev/sda1 so that even after we zap, recreating the drive in the exact sector
position and size will not give us access to the old files in this partition.
root # mkfs.ext2 /dev/sda1
root # sgdisk -Z /dev/sda

Now start the guide again :).

Starting again reusing the same disk partitions and the same pool

If your installation has gotten screwed up for whatever reason and you want to keep your pole named tank than you should boou into the Rescue CD / USB as done before.

import the pool reusing all existing datasets:
root # zpool import -f -R /mnt/funtoo tank

Now you should wipe the previous installation off:

let's go to our base installation directory:
root # cd /mnt/funtoo

and delete the old installation: 
root # rm -rf *

Now start the guide again, at "Pre-Chroot"