ZFS as Root Filesystem

Introduction

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

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.

Booting the ISO

(example using ubuntu live iso 16.04.1 amd64)

ubuntu@ubuntu:~$ sudo -i
root@ubuntu:~# apt-add-repository universe
root@ubuntu:~# apt update
root@ubuntu:~# apt install --yes debootstrap gdisk zfs-initramfs

verify that the ZFS kernel module has loaded

root@ubuntu:~#  dmesg | grep ZFS
[  377.595348] ZFS: Loaded module v0.6.5.6-0ubuntu10, ZFS pool version 5000, ZFS filesystem version 5

Drive Partitions

We are letting ZFS automatically partition the drive. This ideal for our example using a single disk and legacy (BIOS) boot.

Creating of pool

Create a ZFS Storage Pool using a single whole disk

root@ubuntu:~# zpool create -f -o ashift=12 -o cachefile=/tmp/zpool.cache -O normalization=formD -O atime=off -m none -R /mnt/funtoo rpool /dev/disk/by-id/foo

The options used here are

option	description
create	Use zpool to create a ZFS Storage Pool.
-f	Force the use of the selected disk.
-o ashift=12	Alignment of the pool to underlying device sectors. The recommended value is 12, which corresponds to 2^12 Bytes or 4 KiB. This value is typical of drives nowdays. Can only be set at pool creation.
-o cachefile=/tmp/zpool.cache	Create a pool configuration cache and place it in /tmp. This will be required for our Funtoo install.
-O normalization=formD	Recommended. Set the default Unicode (UTF-8) normalization for future filesystems (created within this pool) to 'formD'.
-O atime=off	Optional. As a default preference, set future filesystems (created within this pool) to not update file access time. Useful if wanting to reduce writes to disk (e.g. Solid State Drives). Can cause problems for mailers and other software relying on file access-time data.
-m none	Do not set mountpoint for this storage pool. (This guide will address this later).
-R /mnt/funtoo	Alternate root directory. Essentially a temporary 'mount point' for our pool.
rpool	The name of this ZFS Storage Pool. The pool name is irrelevant, however rpool will be used throughout this guide.
/dev/disk/by-id/foo	The path to the physical disk. e.g. /dev/disk/by-id/ata-Samsung_SSD_840_EVO_120GB_123456789ABCDEF. Known in 'ZFS-speak' as a 'VDEV'.

Please note that the options 'ashift' and 'cachefile' are preceded with a lowercase '-o', while 'normalization' and 'atime' are preceded with an uppercase '-O'.

Without additional options this will create our storage pool and enable all 'features' available under version 0.6.5.6. The pool will be automatically mounted at the (temporary) location /mnt/funtoo.

To confirm the presence of our newly created pool

root@ubuntu:~# zpool status
  pool: rpool
 state: ONLINE
  scan: none requested
config:

	NAME                                             STATE     READ WRITE CKSUM
	rpool                                            ONLINE       0     0     0
	  ata-Samsung_SSD_840_EVO_120GB_123456789ABCDEF  ONLINE       0     0     0

errors: No known data errors

Create ZFS Datasets

Now we will create one or more ZFS filesystems within our storage pool. These will contain Funtoo Linux.

Create the Root file system (Required)

root #  zfs create -o mountpoint=none -o canmount=off 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

Portage directories

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

To confirm the presence of the filesystems that we have created

root@ubuntu:~# zfs list -t all
NAME                USED  AVAIL  REFER  MOUNTPOINT
rpool               660K  19.3G    96K  none
rpool/HOME           96K  19.3G    96K  /mnt/funtoo/home
rpool/ROOT          192K  19.3G    96K  none
rpool/ROOT/funtoo    96K  19.3G    96K  /mnt/funtoo

Make the root filesystem bootable

   Important

Do not skip this!

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

Configure your system according to the main Install Guide. During startup ZFS Filesystems will be mounted without the need of entries in /etc/fstab. Other partitions such as CD-ROMs, tmpfs, etc. should still be included in /etc/fstab.

Next, update the portage tree:

root # emerge --sync
root # env-update
root # source /etc/profile

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. Remember, that we let ZFS partition whole drive. By design, during this, a very small unpartitioned space left at the beginning of the disk. We will use sgdisk, which is part of sys-apps/gptfdisk to format free space into BIOS partition.

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

Installing GRUB2 to disk is as easy as:

root # grub-install /dev/sda

Now it's time for us to create grub's configuration file:

root # grub-mkconfig -O /boot/grub/grub.cfg