.. highlight:: sh

.. ifconfig:: zfs_root_test

 ::

  # For the CI/CD test run of this guide,
  # Enable verbose logging of bash shell and fail immediately when
  # a commmand fails.
  set -vxeuf

  distro=${1}

  cp /etc/resolv.conf ./"rootfs-${distro}"/etc/resolv.conf
  arch-chroot ./"rootfs-${distro}" sh <<-'ZFS_ROOT_GUIDE_TEST'

  set -vxeuf

  # install alpine setup scripts
  apk update
  apk add alpine-conf curl

.. In this document, there are three types of code-block markups:
   ``::`` are commands intended for both the vm test and the users
   ``.. ifconfig:: zfs_root_test`` are commands intended only for vm test
   ``.. code-block:: sh`` are commands intended only for users

Fedora Root on ZFS
=======================================

**Customization**

Unless stated otherwise, it is not recommended to customize system
configuration before reboot.

Preparation
---------------------------

#. Disable Secure Boot. ZFS modules can not be loaded if Secure Boot is enabled.
#. Because the kernel of latest Live CD might be incompatible with
   ZFS, we will use Alpine Linux Extended, which ships with ZFS by
   default.

   Download latest extended variant of `Alpine Linux
   live image
   <https://dl-cdn.alpinelinux.org/alpine/v3.17/releases/x86_64/alpine-extended-3.17.3-x86_64.iso>`__,
   verify `checksum <https://dl-cdn.alpinelinux.org/alpine/v3.17/releases/x86_64/alpine-extended-3.17.3-x86_64.iso.asc>`__
   and boot from it.

   .. code-block:: sh

       gpg --auto-key-retrieve --keyserver hkps://keyserver.ubuntu.com --verify alpine-extended-*.asc

       dd if=input-file of=output-file bs=1M

   .. ifconfig:: zfs_root_test

     # check whether the download page exists
      # alpine version must be in sync with ci/cd test chroot tarball

#. Login as root user.  There is no password.
#. Configure Internet

   .. code-block:: sh

     setup-interfaces -r
     # You must use "-r" option to start networking services properly
     # example:
     network interface: wlan0
     WiFi name:         <ssid>
     ip address:        dhcp
     <enter done to finish network config>
     manual netconfig:  n

#. If you are using wireless network and it is not shown, see `Alpine
   Linux wiki
   <https://wiki.alpinelinux.org/wiki/Wi-Fi#wpa_supplicant>`__ for
   further details.  ``wpa_supplicant`` can be installed with ``apk
   add wpa_supplicant`` without internet connection.

#. Configure SSH server

   .. code-block:: sh

     setup-sshd
     # example:
     ssh server:        openssh
     allow root:        "prohibit-password" or "yes"
     ssh key:           "none" or "<public key>"



#. Set root password or ``/root/.ssh/authorized_keys``.

#. Connect from another computer

   .. code-block:: sh

    ssh root@192.168.1.91

#. Configure NTP client for time synchronization

   .. code-block:: sh

     setup-ntp busybox

   .. ifconfig:: zfs_root_test

     # this step is unnecessary for chroot and returns 1 when executed

#. Set up apk-repo.  A list of available mirrors is shown.
   Press space bar to continue

   .. code-block:: sh

    setup-apkrepos


#. Throughout this guide, we use predictable disk names generated by
   udev

   .. code-block:: sh

     apk update
     apk add eudev
     setup-devd udev

   .. ifconfig:: zfs_root_test

      # for some reason, udev is extremely slow in chroot
      # it is not needed for chroot anyway. so, skip this step

#. Target disk

   List available disks with

   .. code-block:: sh

    find /dev/disk/by-id/

   If virtio is used as disk bus, power off the VM and set serial numbers for disk.
   For QEMU, use ``-drive format=raw,file=disk2.img,serial=AaBb``.
   For libvirt, edit domain XML.  See `this page
   <https://bugzilla.redhat.com/show_bug.cgi?id=1245013>`__ for examples.

   Declare disk array

   .. code-block:: sh

    DISK='/dev/disk/by-id/ata-FOO /dev/disk/by-id/nvme-BAR'

   For single disk installation, use

   .. code-block:: sh

    DISK='/dev/disk/by-id/disk1'

   .. ifconfig:: zfs_root_test

    # for github test run, use chroot and loop devices
    DISK="$(losetup -a| grep fedora | cut -f1 -d: | xargs -t -I '{}' printf '{} ')"

#. Set a mount point
   ::

      MNT=$(mktemp -d)

#. Set partition size:

   Set swap size in GB, set to 1 if you don't want swap to
   take up too much space

   .. code-block:: sh

    SWAPSIZE=4

   .. ifconfig:: zfs_root_test

    # For the test run, use 1GB swap space to avoid hitting CI/CD
    # quota
    SWAPSIZE=1

   Set how much space should be left at the end of the disk, minimum 1GB

   ::

    RESERVE=1

#. Install ZFS support from live media::

    apk add zfs

#. Install partition tool
   ::

      apk add parted e2fsprogs cryptsetup util-linux

System Installation
---------------------------

#. Partition the disks.

   Note: you must clear all existing partition tables and data structures from the disks,
   especially those with existing ZFS pools or mdraid and those that have been used as live media.
   Those data structures may interfere with boot process.

   For flash-based storage, this can be done by the blkdiscard command below:
   ::

     partition_disk () {
      local disk="${1}"
      blkdiscard -f "${disk}" || true

      parted --script --align=optimal  "${disk}" -- \
      mklabel gpt \
      mkpart EFI 2MiB 1GiB \
      mkpart bpool 1GiB 5GiB \
      mkpart rpool 5GiB -$((SWAPSIZE + RESERVE))GiB \
      mkpart swap  -$((SWAPSIZE + RESERVE))GiB -"${RESERVE}"GiB \
      mkpart BIOS 1MiB 2MiB \
      set 1 esp on \
      set 5 bios_grub on \
      set 5 legacy_boot on

      partprobe "${disk}"
     }

     for i in ${DISK}; do
        partition_disk "${i}"
     done

   .. ifconfig:: zfs_root_test

     ::

       # When working with GitHub chroot runners, we are using loop
       # devices as installation target.  However, the alias support for
       # loop device was just introduced in March 2023. See
       # https://github.com/systemd/systemd/pull/26693
       # For now, we will create the aliases maunally as a workaround
       looppart="1 2 3 4 5"
       for i in ${DISK}; do
         for j in ${looppart}; do
           if test -e "${i}p${j}"; then
                    ln -s "${i}p${j}" "${i}-part${j}"
                  fi
         done
       done

#. Setup encrypted swap.  This is useful if the available memory is
   small::

     for i in ${DISK}; do
        cryptsetup open --type plain --key-file /dev/random "${i}"-part4 "${i##*/}"-part4
        mkswap /dev/mapper/"${i##*/}"-part4
        swapon /dev/mapper/"${i##*/}"-part4
     done


#. Load ZFS kernel module

   .. code-block:: sh

       modprobe zfs

#. Create boot pool
   ::

      # shellcheck disable=SC2046
      zpool create -d \
          -o feature@async_destroy=enabled \
          -o feature@bookmarks=enabled \
          -o feature@embedded_data=enabled \
          -o feature@empty_bpobj=enabled \
          -o feature@enabled_txg=enabled \
          -o feature@extensible_dataset=enabled \
          -o feature@filesystem_limits=enabled \
          -o feature@hole_birth=enabled \
          -o feature@large_blocks=enabled \
          -o feature@lz4_compress=enabled \
          -o feature@spacemap_histogram=enabled \
          -o ashift=12 \
          -o autotrim=on \
          -O acltype=posixacl \
          -O canmount=off \
          -O compression=lz4 \
          -O devices=off \
          -O normalization=formD \
          -O relatime=on \
          -O xattr=sa \
          -O mountpoint=/boot \
          -R "${MNT}" \
          bpool \
                 mirror \
          $(for i in ${DISK}; do
             printf '%s ' "${i}-part2";
            done)

   If not using a multi-disk setup, remove ``mirror``.

   You should not need to customize any of the options for the boot pool.

   GRUB does not support all of the zpool features. See ``spa_feature_names``
   in `grub-core/fs/zfs/zfs.c
   <http://git.savannah.gnu.org/cgit/grub.git/tree/grub-core/fs/zfs/zfs.c#n276>`__.
   This step creates a separate boot pool for ``/boot`` with the features
   limited to only those that GRUB supports, allowing the root pool to use
   any/all features.

#. Create root pool
   ::

       # shellcheck disable=SC2046
       zpool create \
           -o ashift=12 \
           -o autotrim=on \
           -R "${MNT}" \
           -O acltype=posixacl \
           -O canmount=off \
           -O compression=zstd \
           -O dnodesize=auto \
           -O normalization=formD \
           -O relatime=on \
           -O xattr=sa \
           -O mountpoint=/ \
           rpool \
           mirror \
          $(for i in ${DISK}; do
             printf '%s ' "${i}-part3";
            done)

   If not using a multi-disk setup, remove ``mirror``.

#. Create root system container:

   - Unencrypted

     ::

      zfs create \
       -o canmount=off \
       -o mountpoint=none \
      rpool/fedora

   - Encrypted:

     Pick a strong password. Once compromised, changing password will not keep your
     data safe. See ``zfs-change-key(8)`` for more info

     .. code-block:: sh

      zfs create \
        -o canmount=off \
               -o mountpoint=none \
               -o encryption=on \
               -o keylocation=prompt \
               -o keyformat=passphrase \
      rpool/fedora

   You can automate this step (insecure) with: ``echo POOLPASS | zfs create ...``.

   Create system datasets,
   manage mountpoints with ``mountpoint=legacy``
   ::

      zfs create -o canmount=noauto -o mountpoint=/  rpool/fedora/root
      zfs mount rpool/fedora/root
      zfs create -o mountpoint=legacy rpool/fedora/home
      mkdir "${MNT}"/home
      mount -t zfs rpool/fedora/home "${MNT}"/home
      zfs create -o mountpoint=legacy  rpool/fedora/var
      zfs create -o mountpoint=legacy rpool/fedora/var/lib
      zfs create -o mountpoint=legacy rpool/fedora/var/log
      zfs create -o mountpoint=none bpool/fedora
      zfs create -o mountpoint=legacy bpool/fedora/root
      mkdir "${MNT}"/boot
      mount -t zfs bpool/fedora/root "${MNT}"/boot
      mkdir -p "${MNT}"/var/log
      mkdir -p "${MNT}"/var/lib
      mount -t zfs rpool/fedora/var/lib "${MNT}"/var/lib
      mount -t zfs rpool/fedora/var/log "${MNT}"/var/log

#. Format and mount ESP
   ::

     for i in ${DISK}; do
      mkfs.vfat -n EFI "${i}"-part1
      mkdir -p "${MNT}"/boot/efis/"${i##*/}"-part1
      mount -t vfat -o iocharset=iso8859-1 "${i}"-part1 "${MNT}"/boot/efis/"${i##*/}"-part1
     done

     mkdir -p "${MNT}"/boot/efi
     mount -t vfat -o iocharset=iso8859-1 "$(echo "${DISK}" | sed "s|^ *||"  | cut -f1 -d' '|| true)"-part1 "${MNT}"/boot/efi

System Configuration 
---------------------------

#. Download and extract minimal Fedora root filesystem::

     apk add curl
     curl --fail-early --fail -L \
     https://dl.fedoraproject.org/pub/fedora/linux/releases/37/Container/x86_64/images/Fedora-Container-Base-37-1.7.x86_64.tar.xz \
     -o rootfs.tar.gz
     curl --fail-early --fail -L \
     https://dl.fedoraproject.org/pub/fedora/linux/releases/37/Container/x86_64/images/Fedora-Container-37-1.7-x86_64-CHECKSUM \
     -o checksum

     # BusyBox sha256sum treats all lines in the checksum file
     # as checksums and requires two spaces "  "
     # between filename and checksum

     grep 'Container-Base' checksum \
     | grep '^SHA256' \
     | sed -E 's|.*= ([a-z0-9]*)$|\1  rootfs.tar.gz|' > ./sha256checksum

     sha256sum -c ./sha256checksum

     rootfs_tar=$(tar t -af rootfs.tar.gz | grep layer.tar)
     rootfs_tar_dir=$(dirname "${rootfs_tar}")
     tar x -af rootfs.tar.gz "${rootfs_tar}"
     ln -s "${MNT}" "${MNT}"/"${rootfs_tar_dir}"
     tar x  -C "${MNT}" -af "${rootfs_tar}"
     unlink "${MNT}"/"${rootfs_tar_dir}"

#. Enable community repo

   .. code-block:: sh

    sed -i '/edge/d' /etc/apk/repositories
    sed -i -E 's/#(.*)community/\1community/' /etc/apk/repositories

#. Generate fstab::

    apk add arch-install-scripts
    genfstab -t PARTUUID "${MNT}" \
    | grep -v swap \
    | sed "s|vfat.*rw|vfat rw,x-systemd.idle-timeout=1min,x-systemd.automount,noauto,nofail|" \
    > "${MNT}"/etc/fstab

#. Chroot

   .. code-block:: sh

    cp /etc/resolv.conf "${MNT}"/etc/resolv.conf
    for i in /dev /proc /sys; do mkdir -p "${MNT}"/"${i}"; mount --rbind "${i}" "${MNT}"/"${i}"; done
    chroot "${MNT}" /usr/bin/env DISK="${DISK}" bash

   .. ifconfig:: zfs_root_test

    cp /etc/resolv.conf "${MNT}"/etc/resolv.conf
    for i in /dev /proc /sys; do mkdir -p "${MNT}"/"${i}"; mount --rbind "${i}" "${MNT}"/"${i}"; done
    chroot "${MNT}" /usr/bin/env DISK="${DISK}" bash <<-'ZFS_ROOT_NESTED_CHROOT'

    set -vxeuf

#. Unset all shell aliases, which can interfere with installation::

     unalias -a

#. Install base packages

   .. code-block:: sh

    dnf -y install @core grub2-efi-x64 \
    grub2-pc grub2-pc-modules grub2-efi-x64-modules shim-x64  \
    efibootmgr kernel kernel-devel

   .. ifconfig:: zfs_root_test

    # no firmware for test
    dnf -y install --setopt=install_weak_deps=False @core grub2-efi-x64 \
    grub2-pc grub2-pc-modules grub2-efi-x64-modules shim-x64  \
    efibootmgr
    # kernel-core

#. Install ZFS packages

   .. code-block:: sh

    dnf -y install \
    https://zfsonlinux.org/fedora/zfs-release-2-2"$(rpm --eval "%{dist}"||true)".noarch.rpm

    dnf -y install zfs zfs-dracut

   .. ifconfig:: zfs_root_test

    # this step will build zfs modules and fail
    # no need to test building in chroot

    dnf -y install \
    https://zfsonlinux.org/fedora/zfs-release-2-2"$(rpm --eval "%{dist}"||true)".noarch.rpm

#. Check whether ZFS modules are successfully built

   .. code-block:: sh

     tail -n10 /var/lib/dkms/zfs/**/build/make.log

     # ERROR: modpost: GPL-incompatible module zfs.ko uses GPL-only symbol 'bio_start_io_acct'
     # ERROR: modpost: GPL-incompatible module zfs.ko uses GPL-only symbol 'bio_end_io_acct_remapped'
     # make[4]:  [scripts/Makefile.modpost:138: /var/lib/dkms/zfs/2.1.9/build/module/Module.symvers] Error 1
     # make[3]:  [Makefile:1977: modpost] Error 2
     # make[3]: Leaving directory '/usr/src/kernels/6.2.9-100.fc36.x86_64'
     # make[2]:  [Makefile:55: modules-Linux] Error 2
     # make[2]: Leaving directory '/var/lib/dkms/zfs/2.1.9/build/module'
     # make[1]:  [Makefile:933: all-recursive] Error 1
     # make[1]: Leaving directory '/var/lib/dkms/zfs/2.1.9/build'
     # make:  [Makefile:794: all] Error 2

   If the build failed, you need to install an Long Term Support
   kernel and its headers, then rebuild ZFS module

   .. code-block:: sh

     # this is a third-party repo!
     # you have been warned.
     #
     # select a kernel from
     # https://copr.fedorainfracloud.org/coprs/kwizart/

     dnf copr enable -y kwizart/kernel-longterm-VERSION
     dnf install -y kernel-longterm kernel-longterm-devel
     dnf remove -y kernel-core

   ZFS modules will be built as part of the kernel installation.
   Check build log again with ``tail`` command.

#. Add zfs modules to dracut

   .. code-block:: sh

    echo 'add_dracutmodules+=" zfs "' >> /etc/dracut.conf.d/zfs.conf
    echo 'force_drivers+=" zfs "' >> /etc/dracut.conf.d/zfs.conf

   .. ifconfig:: zfs_root_test

    # skip this in chroot, because we did not build zfs module

#. Add other drivers to dracut::

    if grep mpt3sas /proc/modules; then
      echo 'force_drivers+=" mpt3sas "'  >> /etc/dracut.conf.d/zfs.conf
    fi
    if grep virtio_blk /proc/modules; then
      echo 'filesystems+=" virtio_blk "' >> /etc/dracut.conf.d/fs.conf
    fi

#. Build initrd
   ::

    find -D exec /lib/modules -maxdepth 1 \
    -mindepth 1 -type d \
    -exec sh -vxc \
    'if test -e "$1"/modules.dep;
       then kernel=$(basename "$1");
       dracut --verbose --force --kver "${kernel}";
     fi' sh {} \;

#. For SELinux, relabel filesystem on reboot::

    fixfiles -F onboot

#. Enable internet time synchronisation::

     systemctl enable systemd-timesyncd

#. Generate host id

   .. code-block:: sh

    zgenhostid -f -o /etc/hostid

   .. ifconfig:: zfs_root_test

    # because zfs is not installed, skip this step

#. Install locale package, example for English locale::

    dnf install -y glibc-minimal-langpack glibc-langpack-en

#. Set locale, keymap, timezone, hostname
   ::

    rm -f /etc/localtime
    systemd-firstboot \
    --force \
    --locale=en_US.UTF-8 \
    --timezone=Etc/UTC \
    --hostname=testhost \
    --keymap=us

#. Set root passwd
   ::

    printf 'root:yourpassword' | chpasswd

Bootloader
---------------------------

#. Apply GRUB workaround

   ::

       echo 'export ZPOOL_VDEV_NAME_PATH=YES' >> /etc/profile.d/zpool_vdev_name_path.sh
       # shellcheck disable=SC1091
       . /etc/profile.d/zpool_vdev_name_path.sh

       # GRUB fails to detect rpool name, hard code as "rpool"
       sed -i "s|rpool=.*|rpool=rpool|"  /etc/grub.d/10_linux

   This workaround needs to be applied for every GRUB update, as the
   update will overwrite the changes.

#. Fedora and RHEL uses Boot Loader Specification module for GRUB,
   which does not support ZFS.  Disable it::

      echo 'GRUB_ENABLE_BLSCFG=false' >> /etc/default/grub

   This means that you need to regenerate GRUB menu and mirror them
   after every kernel update, otherwise computer will still boot old
   kernel on reboot.

#. Install GRUB::

      mkdir -p /boot/efi/fedora/grub-bootdir/i386-pc/
      for i in ${DISK}; do
       grub2-install --target=i386-pc --boot-directory \
           /boot/efi/fedora/grub-bootdir/i386-pc/  "${i}"
      done
      dnf reinstall -y grub2-efi-x64 shim-x64
      cp -r /usr/lib/grub/x86_64-efi/ /boot/efi/EFI/fedora/

#. Generate GRUB menu

   .. code-block:: sh

     mkdir -p /boot/grub2
     grub2-mkconfig -o /boot/grub2/grub.cfg
     cp /boot/grub2/grub.cfg \
      /boot/efi/efi/fedora/grub.cfg
     cp /boot/grub2/grub.cfg \
      /boot/efi/fedora/grub-bootdir/i386-pc/grub2/grub.cfg

   .. ifconfig:: zfs_root_test

    # GRUB menu can not be generated in test due to missing zfs programs

#. For both legacy and EFI booting: mirror ESP content::

    espdir=$(mktemp -d)
    find /boot/efi/ -maxdepth 1 -mindepth 1 -type d -print0 \
    | xargs -t -0I '{}' cp -r '{}' "${espdir}"
    find "${espdir}" -maxdepth 1 -mindepth 1 -type d -print0 \
    | xargs -t -0I '{}' sh -vxc "find /boot/efis/ -maxdepth 1 -mindepth 1 -type d -print0 | xargs -t -0I '[]' cp -r '{}' '[]'"

#. Exit chroot

   .. code-block:: sh

     exit

   .. ifconfig:: zfs_root_test

     # nested chroot ends here
     ZFS_ROOT_NESTED_CHROOT

   .. ifconfig:: zfs_root_test

    ::

     # list contents of boot dir to confirm
     # that the mirroring succeeded
     find "${MNT}"/boot/efis/ -type d > list_of_efi_dirs
     for i in ${DISK}; do
       if ! grep "${i##*/}-part1/efi\|${i##*/}-part1/EFI" list_of_efi_dirs; then
          echo "disk ${i} not found in efi system partition, installation error";
          cat list_of_efi_dirs
          exit 1
       fi
     done

#. Unmount filesystems and create initial system snapshot
   You can later create a boot environment from this snapshot.
   See `Root on ZFS maintenance page <../zfs_root_maintenance.html>`__.
   ::

    umount -Rl "${MNT}"
    zfs snapshot -r rpool@initial-installation
    zfs snapshot -r bpool@initial-installation

#. Export all pools

   .. code-block:: sh

    zpool export -a

   .. ifconfig:: zfs_root_test

    # we are now inside a chroot, where the export will fail
    # export pools when we are outside chroot

#. Reboot

   .. code-block:: sh

     reboot

#. For BIOS-legacy boot users only: the GRUB bootloader installed
   might be unusable.  In this case, see Bootloader Recovery section
   in `Root on ZFS maintenance page <../zfs_root_maintenance.html>`__.

   This issue is not related to Alpine Linux chroot, as Arch Linux
   installed with this method does not have this issue.

   UEFI bootloader is not affected by this issue.

   .. ifconfig:: zfs_root_test

     # chroot ends here
     ZFS_ROOT_GUIDE_TEST

Post installaion
---------------------------

#. Install package groups

   .. code-block:: sh

    dnf group list --hidden -v       # query package groups
    dnf group install gnome-desktop

#. Add new user, configure swap.