make_image_bootable.sh

#!/bin/bash

# Licensed under the Apache License, Version 2.0 (the "License"); you may not use this
# file except in compliance with the License. You may obtain a copy of the License at
# http://www.apache.org/licenses/LICENSE-2.0
# Unless required by applicable law or agreed to in writing, software distributed under
# the License is distributed on an "AS IS" BASIS, WITHOUT WARRANTIES OR CONDITIONS OF
# ANY KIND, either express or implied. See the License for the specific language
# governing permissions and limitations under the License.

######################################################
# This is an example script that works for debian 11 #
######################################################

set -euo pipefail

export DEBIAN_FRONTEND=noninteractive

# This script will run inside the newly installed system, no need to call chroot

# The image contains /etc/mdadm/mdadm.conf which was created by mdadm's postinst script.
# It takes precedence over /etc/mdadm.conf which is generated during partitioning_apply.
# This means /etc/mdadm.conf will never be read so we can delete it.
rm -f /etc/mdadm.conf
# In order to create a prettier config file, we regenerate /etc/mdadm/mdadm.conf
# with a command similar to that of mdadm's postinst script.
/usr/share/mdadm/mkconf force-generate

# Get the right console parameters (including SoL if available) from the rescue's cmdline
console_parameters="$(grep -Po '\bconsole=\S+' /proc/cmdline | paste -s -d" ")"
if ! grep '^GRUB_CMDLINE_LINUX="' /etc/default/grub | grep -qF "$console_parameters"; then
    sed -Ei "s/(^GRUB_CMDLINE_LINUX=.*)\"\$/\1 $console_parameters\"/" /etc/default/grub
fi

# Install ZFS packages if required
if lsblk -lno FSTYPE | grep -qxiF zfs_member; then
    apt-get -y install --no-install-recommends linux-headers-amd64 zfs-dkms zfs-initramfs zfs-zed
    # Make sure zpools are imported at boot, this is not required when / is ZFS because the initramfs
    # imports the pool. However, it is necessary if e.g. /home is ZFS and / is ext4.
    systemctl enable zfs-import-scan.service
fi

if [ -d /sys/firmware/efi ]; then
    echo "INFO - GRUB will be configured for UEFI boot"
    apt-get -y install --no-install-recommends grub-efi-amd64
    # grub-efi-amd64's postinst script does not install GRUB to the EFI partition,
    # it only updates it:
    # https://salsa.debian.org/grub-team/grub/-/commit/74eb20a6d7a3
    # https://salsa.debian.org/grub-team/grub/-/blob/debian/2.04-20/debian/postinst.in#L700
    # This means we need to install GRUB manually (and we do that after installing grub-efi-amd64
    # to prevent it from calling grub-install a second time).
    grub-install --target=x86_64-efi --efi-directory=/boot/efi --no-nvram
    apt-get -y purge grub-pc-bin
else
    echo "INFO - GRUB will be configured for legacy boot"
    realBootDevicesById=()
    read -r bootDevice bootDeviceType < <(findmnt -A -c -e -l -n -T /boot/ -o SOURCE,FSTYPE)
    if [[ "$bootDeviceType" == "zfs" ]]; then
        bootDevices="$(zpool status -LP "${bootDevice%/*}" | grep -Po '/dev/\S+')"
    else
        bootDevices="$bootDevice"
    fi
    realBootDevices="$(lsblk -n -p -b -l -o TYPE,NAME "$bootDevices" -s | awk '$1 == "disk" && !seen[$2]++ {print $2}')"
    # realBootDevices are disks at this point
    for realBootDevice in $realBootDevices; do
        # When GRUB is manually installed, grub-pc/install_devices contains values from /dev/disk/by-id.
        # Each device has two links in that folder, e.g. ata-HGST_HUS726040ALA610_KXXXX and wwn-0x5000cca25defa844.
        # The postinst script for grub-pc keeps the first link after sorting them, see
        # https://salsa.debian.org/grub-team/grub/-/blob/debian/2.04-20/debian/postinst.in#L89
        # Using another link would cause it not to show up in the prompt to reconfigure the package.
        # shellcheck disable=SC2207
        realBootDevicesById+=($(find -L /dev/disk/by-id/ -type b -samefile "$realBootDevice" | sort -us | head -n1))
    done
    # shellcheck disable=SC2001
    echo "grub-pc grub-pc/install_devices multiselect $(sed 's/ /, /g' <<<"${realBootDevicesById[@]}")" | debconf-set-selections
    apt-get -y install --no-install-recommends grub-pc
    apt-get -y purge grub-efi-amd64-bin
fi
apt-get -y autoremove
apt-get -y clean

# Generate a new unique machine-id for this server
systemd-machine-id-setup
# To update mdadm.conf inside the initramfs (it will be the same as /etc/mdadm/mdadm.conf)
# Must run after ZFS installation for ZFS modules to be included if necessary
# and for the initramfs's host id to match that of the real root.
update-initramfs -u

# cleanup
rm -fr /root/.ovh/