ZFS: Difference between revisions

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 == How to install NixOS on a ZFS root filesystem ==
+=== Single-disk ===
+These instructions will get you started with a single-disk ZFS setup. If you're interested in setting up RAID, see below.
+<syntaxhighlight lang="bash">
+# Always use the by-id aliases for devices, otherwise ZFS can choke on imports.
+DISK=/dev/disk/by-id/...
+# Partition 2 will be the boot partition, needed for legacy (BIOS) boot
+sgdisk -a1 -n2:34:2047 -t2:EF02 $DISK
+# If you need EFI support, make an EFI partition:
+sgdisk -n3:1M:+512M -t3:EF00 $DISK
+# Partition 1 will be the main ZFS partition, using up the remaining space on the drive.
+sgdisk -n1:0:0 -t1:BF01 $DISK
+# Create the pool. If you want to tweak this a bit and you're feeling adventurous, you
+# might try adding one or more of the following additional options:
+# To disable writing access times:
+#   -O atime=off
+# To enable filesystem compression:
+#   -O compression=lz4
+# To enable normalizing unicode filenames (and implicitly set utf8only=on):
+#   -O normalization=formD
+# To improve performance of certain extended attributes:
+#   -O xattr=sa
+# To specify that your drive uses 4K sectors instead of relying on the size reported
+# by the hardware:
+#   -O ashift=12
+#
+# The 'mountpoint=none' option disables ZFS's automount machinery; we'll use the
+# normal fstab-based mounting machinery in Linux.
+# '-R /mnt' is not a persistent property of the FS, it'll just be used while we're installing.
+zpool create -O mountpoint=none -R /mnt rpool $DISK-part1
+# Create the filesystems. This layout is designed so that /home is separate from the root
+# filesystem, as you'll likely want to snapshot it differently for backup purposes. It also
+# makes a "nixos" filesystem underneath the root, to support installing multiple OSes if
+# that's something you choose to do in future.
+zfs create -o mountpoint=none rpool/root
+zfs create -o mountpoint=legacy rpool/root/nixos
+zfs create -o mountpoint=legacy rpool/home
+# Mount the filesystems manually. The nixos installer will detect these mountpoints
+# and save them to /mnt/nixos/hardware-configuration.nix during the install process.
+mount -t zfs rpool/root/nixos /mnt
+mkdir /mnt/home
+mount -t zfs rpool/home /mnt/home
+# Generate the NixOS configuration, as per the NixOS manual.
+nixos-generate-config --root /mnt
+# Edit /mnt/etc/nixos/configuration.nix and add the following line:
+## ---8<-------------------------8<---
+  boot.supportedFilesystems = [ "zfs" ];
+## ---8<-------------------------8<---
+# Also, make sure you set the networking.hostId option, which ZFS requires:
+## ---8<-------------------------8<---
+  networking.hostId = "<random 8-digit hex string>"
+## ---8<-------------------------8<---
+# See https://nixos.org/nixos/manual/options.html#opt-networking.hostId for more.
+# Continue with installation!
+nixos-install
+</syntaxhighlight>
+=== With RAID ===
 Here's an example of how to create a ZFS root pool using 4 disks in RAID-10 mode (striping+mirroring), create a ZFS root+home filesystems and install NixOS on them:
@@ Line 138: / Line 206: @@
 <syntaxhighlight lang="bash">
-# Add the zfs filesystem to the install environment:
+# Add the zfs filesystem to the install environment (note this is no longer
+# necessary since nixOS 18.09, as the install environment comes with
+# zfs enabled by default):
 nano /etc/nixos/configuration.nix
@@ Line 151: / Line 221: @@
 # Create boot partition and (zfs) data partition
-# See: https://github.com/zfsonlinux/pkg-zfs/wiki/HOWTO-install-Ubuntu-to-a-Native-ZFS-Root-Filesystem#step-2-disk-partitioning
+# See: https://github.com/zfsonlinux/zfs/wiki/Ubuntu-18.04-Root-on-ZFS#step-2-disk-formatting
 fdisk /dev/sda