From bce90bf7d8ee870e3ce5096c6c4e0440de2988f2 Mon Sep 17 00:00:00 2001
From: Daniel Langbein <daniel@systemli.org>
Date: Tue, 21 Mar 2023 14:11:10 +0100
Subject: [PATCH] v3.0

mkinitcpio or dracut for initramfs generation
---
 PKGBUILD                    |   2 +-
 README.md                   |   2 +-
 de-p1st-installer.sh        | 356 ++++++++++++++++++++++++------------
 example-headless-docker.cfg |  16 +-
 example-vbox.cfg            |  57 ++----
 lib/block-device.sh         | 206 ++++++++++++---------
 lib/user-input.sh           | 144 +++++++--------
 lib/util.sh                 | 103 ++++++-----
 lib/validate-args.sh        |  15 ++
 name-reference-test.sh      |  39 ----
 10 files changed, 531 insertions(+), 409 deletions(-)
 create mode 100644 lib/validate-args.sh
 delete mode 100644 name-reference-test.sh

diff --git a/PKGBUILD b/PKGBUILD
index e6d77d6..0fb668b 100644
--- a/PKGBUILD
+++ b/PKGBUILD
@@ -2,7 +2,7 @@
 _pkgname=installer
 _reponame=arch-installer
 pkgname="de-p1st-$_pkgname"
-pkgver=0.2.4
+pkgver=0.3.0
 pkgrel=1
 pkgdesc="Installer for Arch Linux written in Bash"
 arch=('any')
diff --git a/README.md b/README.md
index 029a84e..2dfdd0e 100644
--- a/README.md
+++ b/README.md
@@ -19,7 +19,7 @@ ls out/out_dir/*.iso
 
 2) Boot into the live medium
 3) Connect to the Internet
-  * [wifi instructions](https://wiki.archlinux.org/title/Iwd#iwctl)
+  * [Wi-Fi instructions](https://wiki.archlinux.org/title/Iwd#iwctl)
 
 **On some other computer:**
 
diff --git a/de-p1st-installer.sh b/de-p1st-installer.sh
index c533e28..07ec9e7 100755
--- a/de-p1st-installer.sh
+++ b/de-p1st-installer.sh
@@ -1,4 +1,4 @@
-#!/bin/bash
+#!/usr/bin/env bash
 # Exit on error.
 set -e
 # Exit on undefined variable reference.
@@ -20,6 +20,8 @@ else
 fi
 
 # Source library files.
+# shellcheck source=lib/validate-args.sh
+source "${lib_dir}"/validate-args.sh
 # shellcheck source=lib/util.sh
 source "${lib_dir}"/util.sh
 # shellcheck source=lib/user-input.sh
@@ -51,40 +53,42 @@ function main() {
   # @post
   #   installation finished
 
+  scrollback
   check_network
   system_time
-  # in: BOOT_FIRMWARE, FS, HOSTNAME, USERNAME, USER_PWD, FDE, LUKS_PWD; (all variables are optional)
-  # out: BOOT_FIRMWARE, FS, HOSTNAME, USERNAME, USER_PWD, FDE, LUKS_PWD (if FDE='true')
-  get_user_input
-  # in: CPU_VENDOR (optional)
-  # out: CPU_VENDOR
-  get_cpu_vendor
+  repository
 
-  # in: FS
+  # in:  BOOT_PART_SIZE, BOOT_FIRMWARE, INITRAMFS, FS, HOSTNAME, USERNAME, USER_PWD, FDE, LUKS_PWD; (all variables are optional)
+  # out: BOOT_PART_SIZE, BOOT_FIRMWARE, INITRAMFS, FS, HOSTNAME, USERNAME, USER_PWD, FDE, LUKS_PWD (if FDE='true')
+  get_user_input
+  # in:  CPU_VENDOR (optional)
+  # out: CPU_VENDOR
+  get_cpu_vendor CPU_VENDOR
+
+  # in:  FS
   # out: FS_DEFAULT_MOUNT_OPTIONS
   get_default_mount_options
-  # in: FS
+  # in:  FS
   # out: FS_ADDITIONAL_MOUNT_OPTIONS
   get_additional_mount_options
 
-  # in: TARGET_BLOCK_DEVICE, BOOT_FIRMWARE
   # out: BOOT_PART, LUKS_PART
-  partition
-  # in: BOOT_FIRMWARE, BOOT_PART, LUKS_PART, FDE, LUKS_PWD, FS
+  partition \
+    "${TARGET_BLOCK_DEVICE}" "${BOOT_FIRMWARE}" "${BOOT_PART_SIZE}" \
+    BOOT_PART LUKS_PART
   # out: LUKS_PART_UUID (if FDE='true'), DATA_PART
-  format
+  format \
+    "${BOOT_PART}" "${LUKS_PART}" "${LUKS_PWD}" "${FDE}" "${FS}" \
+    LUKS_PART_UUID DATA_PART
 
-  # Combine default and additional mount options
-  # out: FS_MOUNT_OPTIONS
-  {
-    TMP1=("${FS_DEFAULT_MOUNT_OPTIONS[@]}" "${FS_ADDITIONAL_MOUNT_OPTIONS[@]}")
-    # Join array elements by ","
-    join_by ',' TMP1 FS_MOUNT_OPTIONS
-  }
+  # Join default and additional mount options by ','
+  # shellcheck disable=SC2034
+  FS_MOUNT_OPTIONS_ARRAY=("${FS_DEFAULT_MOUNT_OPTIONS[@]}" "${FS_ADDITIONAL_MOUNT_OPTIONS[@]}")
+  join_by ',' FS_MOUNT_OPTIONS_ARRAY FS_MOUNT_OPTIONS
 
   mount_partitions
 
-  # in: BOOT_FIRMWARE, PACSTRAP_INTERACTIVE (optional)
+  # in: BOOT_FIRMWARE, INITRAMFS, PACSTRAP_INTERACTIVE (optional)
   run_pacstrap
   # in: FS
   run_genfstab
@@ -94,25 +98,33 @@ function main() {
   # in: USERNAME, USER_PWD, ROOT_PWD (optional)
   user_and_pwd
 
-  sudo arch-chroot /mnt mkinitcpio -P
+  # in: INITRAMFS
+  initramfs
   # in: TARGET_BLOCK_DEVICE, FDE, LUKS_PART_UUID
   bootloader
 
-  if [ "${LEAVE_MOUNTED}" = 'true' ]; then
-    echo 'Leaving partitions below /mnt mounted and '"${DATA_PART}"' opened.'
-  else
-    sudo umount -R /mnt
-    if [ "${FDE}" = 'true' ]; then
-      sudo cryptsetup luksClose "$(basename "${DATA_PART}")"
-    fi
-  fi
+  unmount_partitions
+
   echo 'Finished installation without errors!'
 }
 
+function scrollback(){
+  if ! grep --quiet '^defscrollback' /etc/screenrc; then
+    printf '\n%s\n' "defscrollback 100000" | sudo tee -a /etc/screenrc
+    printf '%s\n' 'Extended screen scrollback history. Pleas create a new screen session and run the installer again.'
+    return 1
+  fi
+
+  if [ -z "${STY:-}" ]; then
+    printf '%s\n' 'Pleas run the installer from a screen session.'
+    return 1
+  fi
+}
+
 function check_network() {
   echo 'Sending ping to wikipedia.de ...'
   ping -c 1 wikipedia.de >/dev/null || {
-    echo 'Pleas set up network access.'
+    echo 'Pleas set up network access and then run the installer again.'
     return 1
   }
 }
@@ -122,6 +134,19 @@ function system_time() {
   timedatectl set-ntp true
 }
 
+function repository(){
+  # Check if the [de-p1st] repository is available.
+  # If not, add it to pacman.conf
+
+  if ! grep --quiet 'de-p1st' /etc/pacman.conf; then
+    printf '%s\n' 'Enabling [de-p1st] package repository:'
+
+    printf '\n%s\n' "[de-p1st]
+SigLevel = Optional TrustAll
+Server = https://arch.p1st.de" | sudo tee -a /etc/pacman.conf
+  fi
+}
+
 function increase_cow_space() {
   # May be useful when running 'pacman -Syu' on the live medium.
   # Usually not necessary!
@@ -138,7 +163,9 @@ function increase_cow_space() {
 
 function get_user_input() {
   # @post
+  #   BOOT_PART_SIZE
   #   BOOT_FIRMWARE: 'uefi' | 'bios'
+  #   INITRAMFS: 'mkinitcpio' | 'dracut'
   #   FS: 'BTRFS' | 'EXT4' | 'F2FS'
   #   FS_BTRFS_SUBVOL_LAYOUT: 'root_only' | '@root@home'
   #   HOSTNAME
@@ -146,15 +173,17 @@ function get_user_input() {
   #   FDE: 'true' | 'false'
   #   LUKS_PWD: only set if FDE='true'
 
-  get_block_devices_with_size
+  # out: BLOCK_DEVICE_SIZES
+  get_block_devices_with_size BLOCK_DEVICE_SIZES
   single_choice_if_empty  TARGET_BLOCK_DEVICE 'Select target device for installation' BLOCK_DEVICE_SIZES
 
+  ask_user_if_empty BOOT_PART_SIZE 'Enter boot partition size in MiB, at least 260:'
+
   if [ "${BOOT_FIRMWARE}" = 'autodetect' ]; then
     # Detect boot firmware type: https://askubuntu.com/a/162573
 
     # Check exit code; if 0 EFI, else BIOS.
-    # "-q": tell grep to output nothing
-    if dmesg | grep -q 'EFI v'; then
+    if dmesg | grep --quiet --fixed-strings 'EFI v'; then
       echo 'Detected EFI boot.'
       BOOT_FIRMWARE='uefi'
     else
@@ -163,46 +192,64 @@ function get_user_input() {
     fi
 
   else  # If $BOOT_FIRMWARE is empty: Let user select BIOS type
-    TMP1=('uefi' 'Newer mainboards' \
-          'bios' 'Legacy BIOS on older mainboards')
-    single_choice_if_empty  BOOT_FIRMWARE 'Select your bios type' TMP1
+    # shellcheck disable=SC2034
+    BOOT_FIRMWARE_QUESTION=('uefi' 'Newer mainboards' \
+                            'bios' 'Legacy BIOS on older mainboards')
+    single_choice_if_empty  BOOT_FIRMWARE 'Select your bios type' BOOT_FIRMWARE_QUESTION
   fi
 
-  TMP1=('BTRFS' 'Allows snapshots and dynamic extension of the FS' \
-        'EXT4'  'Default FS of many distributions' \
-        'F2FS'  'Flash-Friendly-FS for SSD or NVMe')
-  single_choice_if_empty  FS 'Select filesystem to use' TMP1
+  # shellcheck disable=SC2034
+  INITRAMFS_QUESTION=('mkinitcpio' 'Default for Arch Linux' \
+                      'dracut'     'Testing')
+  single_choice_if_empty  INITRAMFS 'Select filesystem to use' INITRAMFS_QUESTION
+
+  # shellcheck disable=SC2034
+  FS_QUESTION=('BTRFS' 'Allows snapshots and dynamic extension of the FS' \
+               'EXT4'  'Default FS of many distributions' \
+               'F2FS'  'Flash-Friendly-FS for SSD or NVMe')
+  single_choice_if_empty  FS 'Select filesystem to use' FS_QUESTION
 
   if [ "${FS}" = 'BTRFS' ]; then
-    TMP1=('root_only'  'Just one subvolume for "/".' \
+    # shellcheck disable=SC2034
+    FS_QUESTION2=('root_only'  'Just one subvolume for "/".' \
           '@root@home' 'Two subvolumes @ and @home. This configuration allows usage of "Timeshift".')
-    single_choice_if_empty  FS_BTRFS_SUBVOL_LAYOUT 'Select your preferred subvolume layout' TMP1
+    single_choice_if_empty  FS_BTRFS_SUBVOL_LAYOUT 'Select your preferred subvolume layout' FS_QUESTION2
   fi
 
   ask_user_if_empty HOSTNAME 'Enter hostname:'
   ask_user_if_empty USERNAME 'Enter username:'
 
+  # If USER_PWD is  empty
   if [ -z "${USER_PWD}" ]; then
     ask_user_if_empty USER_PWD 'Enter a user password:'
     ask_user_if_empty USER_PWD2 'Please enter the password again:'
     # shellcheck disable=SC2153
-    [[ "${USER_PWD}" == "${USER_PWD2}" ]] || {
+    if [ "${USER_PWD}" != "${USER_PWD2}" ]; then
       echo 'Passwords did not match'
       exit 1
-    }
+    fi
   fi
 
-  TMP1=('true' 'Yes' 'false' 'No')
-  single_choice_if_empty  FDE 'Shall Full-Disk-Encryption be enabled?' TMP1
+  # shellcheck disable=SC2034
+  FDE_QUESTION=('true' 'Yes' 'false' 'No')
+  single_choice_if_empty  FDE 'Shall Full-Disk-Encryption be enabled?' FDE_QUESTION
 
+  # If FDE enabled but LUKS_PWD is  empty
   if [ "${FDE}" = 'true' ] && [ -z "${LUKS_PWD}" ]; then
     ask_user_if_empty LUKS_PWD 'Enter a disk encryption password:'
     ask_user_if_empty LUKS_PWD2 'Please enter the password again:'
     # shellcheck disable=SC2153
-    [[ "${LUKS_PWD}" == "${LUKS_PWD2}" ]] || {
+    if [ "${LUKS_PWD}" != "${LUKS_PWD2}" ]; then
       echo 'Passwords did not match'
       exit 1
-    }
+    fi
+  fi
+
+  # ADDITIONAL_PKGS is an array, but all elements should be non-empty.
+  # Thus, it is ok if we do only check the first element.
+  if [ -z "${ADDITIONAL_PKGS:-}" ]; then
+    ask_user_if_empty ADDITIONAL_PKGS 'Additional packages to install (separated by space):'
+    space_separated_to_array ADDITIONAL_PKGS ADDITIONAL_PKGS || return $?
   fi
 }
 
@@ -225,9 +272,7 @@ function get_default_mount_options() {
 		FS_DEFAULT_MOUNT_OPTIONS+=('compress=zstd:1')
 		;;
 	EXT4)
-	  # https://wiki.archlinux.org/index.php/Ext4#Enabling_metadata_checksums
-	  # If the CPU supports SSE 4.2, make sure the crc32c_intel kernel module is loaded
-		FS_DEFAULT_MOUNT_OPTIONS+=('metadata_csum')
+		FS_DEFAULT_MOUNT_OPTIONS+=()
 		;;
   F2FS)
     # When mounting the filesystem, specify compress_algorithm=(lzo|lz4|zstd|lzo-rle).
@@ -250,19 +295,19 @@ function get_additional_mount_options() {
   case "${FS}" in
 	BTRFS)
 	  # noatime, nodiratime:
-	  # - The atime options do impact drive performance;
-	  # - noatime implies nodiratime, one does not need to specify both;
-	  # - The noatime option fully disables writing file access times to the drive every time you read a file.
+	  # - `atime` impacts drive performance
+	  # - `noatime` implies `nodiratime`, one does not need to specify both
+	  # - `noatime` fully disables writing file access times to the drive every time you read a file.
 	  #   This works well for almost all applications, except for those that need to know if a file has been
 	  #   read since the last time it was modified.
-	  TMP1=('noatime' 'Don'\''t write file/folder access times' 'on' 'ssd' 'Enable if using SSD/NVMe' 'off')
+	  FS_ADDITIONAL_MOUNT_OPTIONS_QUESTION=('noatime' 'Don'\''t write file/folder access times' 'on' 'ssd' 'Enable if using SSD/NVMe' 'off')
 		;;
 	EXT4)
-	  TMP1=('noatime' 'Don'\''t write file/folder access times' 'on')
+	  FS_ADDITIONAL_MOUNT_OPTIONS_QUESTION=('noatime' 'Don'\''t write file/folder access times' 'on')
 		;;
   F2FS)
     # shellcheck disable=SC2034
-    TMP1=('noatime' 'Don'\''t write file/folder access times' 'on')
+    FS_ADDITIONAL_MOUNT_OPTIONS_QUESTION=('noatime' 'Don'\''t write file/folder access times' 'on')
     ;;
 	*)
 		echo 'Filesystem '"${FS}"' not yet supported!'
@@ -270,7 +315,7 @@ function get_additional_mount_options() {
 		;;
   esac
 
-  multi_choice_if_empty  FS_ADDITIONAL_MOUNT_OPTIONS 'Select mount options' TMP1
+  multi_choice_if_empty  FS_ADDITIONAL_MOUNT_OPTIONS 'Select mount options' FS_ADDITIONAL_MOUNT_OPTIONS_QUESTION
 }
 
 function mount_partitions() {
@@ -316,6 +361,9 @@ function mount_partitions() {
   echo 'Mounting boot partition ...'
   sudo mkdir /mnt/boot
   sudo mount "${BOOT_PART}" /mnt/boot
+
+  # Print information about partitions.
+  lsblk --tree=PATH -o PATH,TYPE,UUID
 }
 
 function run_pacstrap() {
@@ -340,24 +388,37 @@ function run_pacstrap() {
     ;;
   esac
 
-  # If CPU_VENDOR is not empty, then
-  if [ -n "${CPU_VENDOR}" ]; then
-    case "${CPU_VENDOR}" in
-    amd)
-      PKGS+=('de-p1st-ucode-amd')
-      ;;
-    intel)
-      PKGS+=('de-p1st-ucode-intel')
-      ;;
-    none)
-      PKGS+=('de-p1st-ucode-placeholder')
-      ;;
-    *)
-      echo 'Invalid option: '"${CPU_VENDOR}"
-      return 1
-      ;;
-    esac
-  fi
+  case "${INITRAMFS}" in
+  mkinitcpio)
+    PKGS+=('de-p1st-mkinitcpio')
+    ;;
+  dracut)
+    PKGS+=('dracut')
+    # PKGS+=('binutils') # for --uefi (Unified Kernel Image) option
+    PKGS+=('elfutils') # reduced initramfs size
+    PKGS+=('multipath-tools') # dracut module support
+    ;;
+  *)
+    echo 'Invalid option: '"${INITRAMFS}"
+    return 1
+    ;;
+  esac
+
+  case "${CPU_VENDOR}" in
+  amd)
+    PKGS+=('de-p1st-ucode-amd')
+    ;;
+  intel)
+    PKGS+=('de-p1st-ucode-intel')
+    ;;
+  none)
+    PKGS+=('de-p1st-ucode-none')
+    ;;
+  *)
+    echo 'Invalid option: '"${CPU_VENDOR}"
+    return 1
+    ;;
+  esac
 
   local args=()
   if [ "${PACSTRAP_INTERACTIVE}" = 'true' ]; then
@@ -380,7 +441,7 @@ function run_genfstab() {
 	  # Remove "subvolid=..." mount option but leave "subvol=..." mount option
 	  fstab=$(printf '%s' "${fstab}" | sed 's/,subvolid=[^,\s]\+//')
 	  # Check if fstab does still contain subvolid mount option
-    if printf '%s' "${fstab}" | grep -q 'subvolid='; then
+    if printf '%s' "${fstab}" | grep --quiet 'subvolid='; then
 	    echo 'This should not happen!'
 	    return 1
     fi
@@ -392,12 +453,13 @@ function run_genfstab() {
     true
     ;;
 	*)
-		echo 'Filesystem '"${FS}"' not yet supported!'
+		printf '%s\n' "Filesystem ${FS} not yet supported!"
 		return 1
 		;;
   esac
 
-  printf '%s' "${fstab}" | sudo tee /mnt/etc/fstab >/dev/null
+  echo 'Generating fstab'
+  printf '%s' "${fstab}" | sudo tee /mnt/etc/fstab
 }
 
 function config_hostname_and_hosts() {
@@ -448,20 +510,77 @@ function user_and_pwd() {
   sudo arch-chroot /mnt useradd -m -s /usr/bin/zsh -g wheel "${USERNAME}"
   sudo arch-chroot /mnt chsh       -s /usr/bin/zsh
 
-  # If ROOT_PWD is not given, the use USER_PWD for root user
-  ROOT_PWD="${ROOT_PWD:="${USER_PWD}"}"
+  if [ -z "${ROOT_PWD:-}" ]; then
+    printf '%s\n' 'No root password given, using the user password for root'
+    ROOT_PWD="${USER_PWD}"
+  fi
 
   printf '%s:%s' "${USERNAME}" "${USER_PWD}" | sudo chpasswd --root /mnt
   printf '%s:%s' "root"        "${ROOT_PWD}" | sudo chpasswd --root /mnt
 }
 
+function initramfs(){
+  # @pre
+  #   INITRAMFS
+
+  case "${INITRAMFS}" in
+  mkinitcpio)
+    sudo arch-chroot /mnt mkinitcpio -P
+    ;;
+  dracut)
+    # configuration
+    install -m0644 /dev/stdin /mnt/etc/dracut.conf.d/de-p1st.conf << 'EOF'
+# --fstab
+use_fstab=yes
+# --show-modules
+show_modules=yes
+
+# https://wiki.archlinux.org/title/Dracut#LVM_/_software_RAID_/_LUKS
+kernel_cmdline="rd.auto rd.luks=1"
+EOF
+
+    # TODO:
+    #   Use a hook to do this
+    #   on the running system after each
+    #   kernel upgrade.
+
+    # https://wiki.archlinux.org/title/Dracut#Generate_a_new_initramfs_on_kernel_upgrade
+    #   - detect kernel version
+    #   - install vmlinuz
+    #   - run dracut
+
+    for module in /mnt/lib/modules/*; do
+      kernel="$(basename "${module}")"
+      pkgbase="$(cat "${module}/pkgbase")"
+
+      install -Dm644 "${module}/vmlinuz" "/mnt/boot/vmlinuz-${pkgbase}"
+
+      echo 'Kernel command line:'
+      arch-chroot /mnt dracut \
+        --kver "${kernel}" \
+        --print-cmdline \
+        "/boot/initramfs-${pkgbase}.img"
+
+      echo 'Creating initramfs:'
+      arch-chroot /mnt dracut \
+        --kver "${kernel}" \
+        "/boot/initramfs-${pkgbase}.img"
+    done
+    ;;
+  *)
+    echo 'Invalid option: '"${INITRAMFS}"
+    return 1
+    ;;
+  esac
+}
+
 function bootloader() {
   # @pre
   #   TARGET_BLOCK_DEVICE
   #   FDE: 'true' | 'false'
   #   LUKS_PART_UUID: required if FDE='true'
 
-  echo 'Installing grub ...'
+  echo 'Installing grub:'
   case "${BOOT_FIRMWARE}" in
   uefi)
     # Portable fallback efi name for grub:
@@ -478,40 +597,47 @@ function bootloader() {
     ;;
   esac
 
-  echo 'Generating /boot/grub/grub.cfg ...'
-  {
-    case "${FDE}" in
-    true)
-      # /etc/default/grub is managed by Holo. Therefore we should not manually modify it.
-      # Instead, we create a holosript which writes $LUKS_PART_UUID into GRUB_CMDLINE_LINUX of /etc/default/grub
-      {
-        # Assert
-        grep --quiet '^GRUB_CMDLINE_LINUX=""$' < /mnt/etc/default/grub || return
+  # grub.cfg adjustments
+  if [ "${INITRAMFS}" = 'mkinitcpio' ] && [ "${FDE}" = "true" ]; then
+    # /etc/default/grub is managed by Holo. Therefore we should not manually modify it.
+    # Instead, we create a holosript which writes $LUKS_PART_UUID into GRUB_CMDLINE_LINUX of /etc/default/grub
+    {
+      # Use filename .../20- for the holoscript so that it gets executed after the one from de-p1st-grub
+      local holoScriptDir=/mnt/usr/share/holo/files/20-de-p1st-installer/etc/default/
+      # The holoscript shall contain one 'sed "..."' command
+      sudo mkdir -p "${holoScriptDir}"
+      sudo echo "#!/bin/sh
+py-regex-replace -p '^GRUB_CMDLINE_LINUX=\"\"\$' -r 'GRUB_CMDLINE_LINUX=\"cryptdevice=/dev/disk/by-uuid/${LUKS_PART_UUID}:crypt\"'
+" | sudo tee "${holoScriptDir}"/grub.holoscript
+      sudo chmod 0544 "${holoScriptDir}"/grub.holoscript
+    }
+    # Then we apply the holoscript
+    sudo arch-chroot /mnt holo apply --force file:/etc/default/grub
 
-        # Use filename .../20- for the holoscript so that it gets executed after the one from de-p1st-grub
-        local holoScriptDir=/mnt/usr/share/holo/files/20-de-p1st-installer/etc/default/
-        # The holoscript shall contain one 'sed "..."' command
-        sudo mkdir -p "${holoScriptDir}"
-        sudo echo '#!/bin/sh
-sed "s|^GRUB_CMDLINE_LINUX=\"\"\$|GRUB_CMDLINE_LINUX=\"cryptdevice=/dev/disk/by-uuid/'"${LUKS_PART_UUID}"':crypt\"|"' \
-          | sudo tee "${holoScriptDir}"/grub.holoscript
-        sudo chmod 0544 "${holoScriptDir}"/grub.holoscript
-      }
-      # Then we apply the holoscript
-      sudo arch-chroot /mnt holo apply --force file:/etc/default/grub
-      ;;
-    false)
-      true
-      ;;
-    *)
-      echo 'Invalid option: '"${FDE}"
-      return 1
-      ;;
-    esac
+    # Print start of grub file containing GRUB_CMDLINE_LINUX
+    head /mnt/etc/default/grub
+  fi
 
-    # And finally run grub-mkconfig
-    sudo arch-chroot /mnt grub-mkconfig -o /boot/grub/grub.cfg
-  }
+  echo 'Generating /boot/grub/grub.cfg:'
+  sudo arch-chroot /mnt grub-mkconfig -o /boot/grub/grub.cfg
+
+  if [ "${INITRAMFS}" = 'mkinitcpio' ] && [ "${FDE}" = "true" ]; then
+    printf '%s\n' 'Occurrence of "cryptdevice" in /boot/grub/grub.cfg:'
+    grep 'cryptdevice' /mnt/boot/grub/grub.cfg
+  fi
+}
+
+function unmount_partitions(){
+  if [ "${LEAVE_MOUNTED}" = 'true' ]; then
+    echo 'Leaving partitions below /mnt mounted and '"${DATA_PART}"' opened.'
+  else
+    echo 'unmount /mnt'
+    sudo umount -R /mnt
+    if [ "${FDE}" = 'true' ]; then
+      echo "luksClose ${DATA_PART}"
+      sudo cryptsetup luksClose "$(basename "${DATA_PART}")"
+    fi
+  fi
 }
 
 main "$@"
diff --git a/example-headless-docker.cfg b/example-headless-docker.cfg
index 87d37ad..71fb687 100644
--- a/example-headless-docker.cfg
+++ b/example-headless-docker.cfg
@@ -3,26 +3,30 @@
 FQDN=v2202012136854137045.happysrv.de
 STATIC_IP=45.83.105.88
 IPV6_CAPABLE=true
-HOSTNAME=p1st-arch-1
+HOSTNAME=netcup-example
 USERNAME=yoda
 
+FDE=false
+
 TARGET_BLOCK_DEVICE=/dev/sda
-BOOT_PART_SIZE=500  # MiB
+BOOT_PART_SIZE=260
+
 FS=BTRFS
 FS_ADDITIONAL_MOUNT_OPTIONS=('noatime')
 
 CPU_VENDOR=none
 BOOT_FIRMWARE=uefi
+INITRAMFS=dracut
 
 LEAVE_MOUNTED=false
 PACSTRAP_INTERACTIVE=true
 
+############## ADDITIONAL_PKGS from here on ##############
 ADDITIONAL_PKGS=()
-# to skip pacman selections
-ADDITIONAL_PKGS+=('mkinitcpio' 'de-p1st-kernel-lts' 'de-p1st-ucode-placeholder' 'qemu-guest-agent')
-# remote ssh access
+
+# Remote SSH access
 ADDITIONAL_PKGS+=('de-p1st-ssh' 'de-p1st-ssh-key-yoda')
-# docker and docker-compose
+# Docker and Docker Compose
 ADDITIONAL_PKGS+=('de-p1st-docker')
 # cronie
 ADDITIONAL_PKGS+=('de-p1st-cronie')
diff --git a/example-vbox.cfg b/example-vbox.cfg
index 7390dc7..c4bb2ec 100644
--- a/example-vbox.cfg
+++ b/example-vbox.cfg
@@ -1,64 +1,47 @@
 # Example config for testing in VirtualBox
 
-# FQDN=domain.name.of.this.host.de
-# STATIC_IP=123.123.123.123
-# IPV6_CAPABLE=true
+#FQDN=domain.name.of.this.host.de
+#STATIC_IP=123.123.123.123
+# IPV6_CAPABLE: 'true' | 'false'
+IPV6_CAPABLE=true
 HOSTNAME=yodaTest
 USERNAME=yoda
 
-# One should rather enter these interactively than saving in this cfg.
 USER_PWD='test'
-FDE=false  # enable FULL-DISK-ENCRYPTION
+#ROOT_PWD=test
+
+# FDE: 'true' | 'false'
+FDE=true
 LUKS_PWD='test'
 
-# If unset, then USER_PWD will be used for ROOT_PWD
-# ROOT_PWD=test
-
 TARGET_BLOCK_DEVICE=/dev/sda  # /dev/vda for Virtual Machine Manager
-BOOT_PART_SIZE=500  # MiB
+# BOOT_PART_SIZE: in MiB, at least 260
+BOOT_PART_SIZE=260
+
+# FS: 'BTRFS' | 'EXT4' | 'F2FS'
 FS=BTRFS
-FS_BTRFS_SUBVOL_LAYOUT='@root@home'  # Subvolume layout that is supported by Timeshift
+# FS_BTRFS_SUBVOL_LAYOUT: 'root_only' | '@root@home'
+FS_BTRFS_SUBVOL_LAYOUT='@root@home'
 FS_ADDITIONAL_MOUNT_OPTIONS=('noatime')
 
 # If not booted into the target system, these values should be set:
 # CPU_VENDOR: 'autodetect' | 'amd' | 'intel' | 'none'
-CPU_VENDOR=autodetect
+CPU_VENDOR=none
 # BOOT_FIRMWARE: 'autodetect' | 'uefi' | 'bios'
 BOOT_FIRMWARE=uefi
+# INITRAMFS: 'mkinitcpio' | 'dracut'
+INITRAMFS=dracut
 
 # If set to 'true', then the data, boot and luks partitions
 # will be left mounted/opened for manual inspection
 # after the installation
-LEAVE_MOUNTED=true
+# LEAVE_MOUNTED: 'true' | 'false'
+LEAVE_MOUNTED=false
+# PACSTRAP_INTERACTIVE: 'true' | 'false'
 PACSTRAP_INTERACTIVE=true
 
 ############## ADDITIONAL_PKGS from here on ##############
 ADDITIONAL_PKGS=()
 
-# Specify the preferred providers for initramfs, de-p1st-kernel, de-p1st-ucode, de-p1st-sddm-theme
-ADDITIONAL_PKGS+=('mkinitcpio' 'de-p1st-kernel-lts' 'de-p1st-ucode-placeholder' 'de-p1st-sddm-theme-nordic')
 # VBox guest additions
 ADDITIONAL_PKGS+=('virtualbox-guest-utils')
-# XFCE4 desktop with HiDPI
-ADDITIONAL_PKGS+=('de-p1st-gpu-generic' 'de-p1st-xfce4-hidpi' 'de-p1st-sddm-tablet')
-# To be able to install ungoogled-chromium
-ADDITIONAL_PKGS+=('de-p1st-pacman-repo-chromium')
-
-# If your network is unsafe, e.g. if you live in Germany, then include a VPN client
-ADDITIONAL_PKGS+=('riseup-vpn')
-# Smartcard (e.g. Nitrokey or Yubikey)
-ADDITIONAL_PKGS+=('de-p1st-smartcard')
-
-
-# Other programs
-ADDITIONAL_PKGS+=('firefox' 'signal-desktop' 'nextcloud-client' 'keepassxc' 'xournalpp' 'zotero')
-# Development
-ADDITIONAL_PKGS+=('intellij-idea-ultimate-edition' 'intellij-idea-ultimate-edition-jre')
-# Document viewer
-ADDITIONAL_PKGS+=('evince')
-# Gallery / image viewer
-ADDITIONAL_PKGS+=('nomacs' 'qt5-imageformats')
-# LibreOffice with spell checking (de, us) and hyphenation rules (de, us)
-ADDITIONAL_PKGS+=('libreoffice-fresh')
-ADDITIONAL_PKGS+=('hunspell-de' 'hunspell-en_US')
-ADDITIONAL_PKGS+=('hyphen' 'hyphen-de' 'hyphen-en')
diff --git a/lib/block-device.sh b/lib/block-device.sh
index f338caf..838fbf5 100644
--- a/lib/block-device.sh
+++ b/lib/block-device.sh
@@ -6,87 +6,103 @@
 # -l, --list        Produce  output  in the form of a list.
 # -n, --noheadings
 # -x, --sort column
+#
+# lsblk --tree=PATH -o PATH,TYPE,PARTUUID
 
 function get_uuid() {
   # arg $1: Partition
   # arg $2: Variable name to store UUID
+  validate_args 2 "$@" || return $?
+  local partition="${1}"
+  local -n uuid_ptr=$2
 
-  local -n ptr=$2  || return $?
   # shellcheck disable=SC2034
-  ptr="$(blkid -o value -s UUID "${1}")" || return $?
+  uuid_ptr="$(blkid -o value -s UUID "${partition}")" || return $?
 }
 
 function get_partitions(){
-  # arg $1: block-device
-  # @post
-  #   PARTITIONS (array with one partition per entry)
+  # arg $1: block device
+  # arg $2: name of variable to store partitions
+  validate_args 2 "$@" || return $?
+  local block_device="$1"
+  local -n partitions_ptr=$2
 
-  # Remove first line of output (which is just the block device $1 itself)
-  # with sed: sed 1d
-  PARTITIONS="$(lsblk -pln -o name "${1}" | sed 1d)" || return $?
+  # Remove first line of output (which is just the block device itself)
+  # with sed: `sed 1d`
+  # shellcheck disable=SC2034
+  partitions_ptr="$(lsblk -pln -o name "${block_device}" | sed 1d)" || return $?
 
-  newline_separated_to_array PARTITIONS PARTITIONS || return $?
+  newline_separated_to_array partitions_ptr partitions_ptr || return $?
 }
 
 function get_block_devices() {
-  # @post
-  #   BLOCK_DEVICES (array with one entry for each block device)
+  # arg $1: name of variable to store block devices
+  validate_args 1 "$@" || return $?
+  local -n block_devices_ptr=$1
 
   # Get list of devices, one per line
-  BLOCK_DEVICES="$(lsblk -dplnx size -o name | grep -Ev 'boot|rpmb|loop' | tac)" || return $?
+  # shellcheck disable=SC2034
+  block_devices_ptr="$(lsblk -dplnx size -o name | grep -Ev 'boot|rpmb|loop' | tac)" || return $?
 
-  newline_separated_to_array BLOCK_DEVICES  BLOCK_DEVICES || return $?
+  newline_separated_to_array block_devices_ptr block_devices_ptr || return $?
 }
 
 function get_block_devices_with_size() {
-  # @post
-  #   BLOCK_DEVICE_SIZES (array with two entries for each block device: device path and device size)
+  # Example: variable with name $1 has content ('/dev/nvme0n1' '1,9T')
+  #
+  # arg $1: name of variable to store block device paths and their sizes
+  validate_args 1 "$@" || return $?
+  local -n block_device_sizes_ptr=$1
 
   # Get list of devices and their sizes, one pair per line.
   # Use sed to remove multiple white spaces: sed 's|\s\s*| |'
-  BLOCK_DEVICE_SIZES="$(lsblk -dplnx size -o name,size | grep -Ev 'boot|rpmb|loop' | sed 's|\s\s*| |' | tac)"  || return $?
+  # shellcheck disable=SC2034
+  block_device_sizes_ptr="$(lsblk -dplnx size -o name,size | grep -Ev 'boot|rpmb|loop' | sed 's|\s\s*| |' | tac)"  || return $?
 
-  newline_to_space BLOCK_DEVICE_SIZES || return $?
-  space_separated_to_array BLOCK_DEVICE_SIZES BLOCK_DEVICE_SIZES || return $?
+  newline_to_space block_device_sizes_ptr || return $?
+  space_separated_to_array block_device_sizes_ptr block_device_sizes_ptr || return $?
 }
 
-
 function partition() {
   # Creates two partitions:
-  # - BOOT_PART by default 261mb
-  # - LUKS_PART rest of the device for (encrypted) data
+  # - boot partition, by default 260MiB
+  # - luks partition, rest of the device for (encrypted) data
   #
-  # @pre
-  #   TARGET_BLOCK_DEVICE
-  #   BOOT_FIRMWARE
-  # @post
-  #   BOOT_PART
-  #   LUKS_PART
+  # arg $1: target block device
+  # arg $2: boot firmware: 'uefi' | 'bios'
+  # arg $3: boot partition size in MiB: >=260 | 'none'
+  # arg $4: name of variable to store boot partition
+  # arg $5: name of variable to store luks partition
+  validate_args 5 "$@" || return $?
+  local target_block_device="${1}"
+  local boot_firmware="${2}"
+  local boot_part_size="${3}"
+  local -n boot_part=$4
+  local -n luks_part=$5
 
-  # If BOOT_PART_SIZE not given, set to default value
-  BOOT_PART_SIZE="${BOOT_PART_SIZE:='261'}"
-  # If too small, print warning and exit
-  if [ "${BOOT_PART_SIZE}" -lt '261' ]; then
-    echo 'BOOT_PART_SIZE should be larger than 260!';
-    return 1;
+  local minimum=260
+  # Check if too small
+  if [ "${boot_part_size}" -lt "${minimum}" ]; then
+    printf '%s\n' "boot_part_size should be >= ${minimum}"
+    return 1
   fi
 
   # As our data partition is encrypted,
   # we need a separate boot partition!
-  case "${BOOT_FIRMWARE}" in
+  case "${boot_firmware}" in
 	uefi)
 	  # EFI boot partition
     #
     # Create a partition with fat32 as the file system type and set the
     # esp flag on it.
-    sudo parted --script "${TARGET_BLOCK_DEVICE}" -- mklabel gpt \
-      mkpart ESP fat32 2Mib "${BOOT_PART_SIZE}MiB" \
+    sudo parted --script "${target_block_device}" -- mklabel gpt \
+      mkpart ESP fat32 2Mib "${boot_part_size}MiB" \
       set 1 esp on \
-      mkpart primary "${BOOT_PART_SIZE}MiB" 100% || return $?
+      mkpart primary "${boot_part_size}MiB" 100% || return $?
 
-    get_partitions "${TARGET_BLOCK_DEVICE}" || return $?
-    BOOT_PART="${PARTITIONS[0]}"
-    LUKS_PART="${PARTITIONS[1]}"
+    get_partitions "${target_block_device}" PARTITIONS || return $?
+    boot_part="${PARTITIONS[0]}"
+    luks_part="${PARTITIONS[1]}"
 		;;
 	bios)
 	  # > On a BIOS/GPT configuration, a BIOS boot partition is required. GRUB embeds its `core.img`
@@ -95,97 +111,111 @@ function partition() {
 	  #
 	  # archwiki -> GRUB#GUID_Partition_Table_(GPT)_specific_instructions
 	  # https://www.gnu.org/software/grub/manual/grub/html_node/BIOS-installation.html#BIOS-installation
-	  sudo parted --script "${TARGET_BLOCK_DEVICE}" -- mklabel gpt \
+	  sudo parted --script "${target_block_device}" -- mklabel gpt \
       mkpart primary 1MiB 2MiB \
       set 1 bios_grub on \
-      mkpart primary 2MiB "${BOOT_PART_SIZE}MiB" \
-      mkpart primary "${BOOT_PART_SIZE}MiB" 100% || return $?
+      mkpart primary 2MiB "${boot_part_size}MiB" \
+      mkpart primary "${boot_part_size}MiB" 100% || return $?
 
-    get_partitions "${TARGET_BLOCK_DEVICE}" || return $?
-    BOOT_PART="${PARTITIONS[2]}"
-    LUKS_PART="${PARTITIONS[3]}"
+    get_partitions "${target_block_device}" PARTITIONS || return $?
+    boot_part="${PARTITIONS[2]}"
+    luks_part="${PARTITIONS[3]}"
 		;;
 	*)
-		echo 'Expected uefi or bios but got '"${BOOT_FIRMWARE}"' instead!'
+		printf '%s\n'  "Expected uefi or bios but got ${boot_firmware} instead!"
 		return 1
 		;;
   esac
 
-  echo 'boot partition: '"${BOOT_PART}"
-  echo 'luks partition: '"${LUKS_PART}"
+  printf '%s\n' "boot partition: ${boot_part}"
+  printf '%s\n' "luks partition: ${luks_part}"
 }
 
 function format() {
-  # Formats BOOT_PART and LUKS_PART.
-  # If encryption is enabled (FDE='true'), then an encrypted partition will be created at LUKS_PART
-  # which can be accessed under DATA_PART.
-  # If encryption is disabled, then DATA_PART is identical to LUKS_PART.
+  # Formats the `boot` and `luks` partitions.
+  #
+  # If FDE is enabled ('true'),
+  # then $2 will be encrypted with password $3 and opened at $7.
+  #
+  # If FDE is disabled,
+  # then $7 is identical with $2.
+  #
+  # arg $1: boot partition
+  # arg $2: (encrypted) luks partition
+  # arg $3: password of luks partition
+  # arg $4: full-disk-encryption (FDE): 'true' | 'false'
+  # arg $5: filesystem: 'BTRFS' | 'EXT4' | 'F2FS'
+  # arg $6: name of variable to store partition of encrypted luks partition (if FDE='true').
+  #         Set to /dev/mapper/$(basename $LUKS_PART)
+  # arg $7: name of variable to store data partition
   #
-  # @pre
-  #   BOOT_FIRMWARE
-  #   BOOT_PART
-  #   LUKS_PART
-  #   LUKS_PWD
-  #   FDE: 'true' | 'false'
-  #   FS
   # @post
-  #   LUKS_PART_UUID: only set if FDE='true'
-  #   DATA_PART: if FDE='true', then set to /dev/mapper/$(basename "${LUKS_PART}")
   #   boot partition formatted
-  #   luks partition formatted and accessible under DATA_PART
+  #   luks partition formatted and accessible under $7
+  validate_args 7 "$@" || return $?
+  local boot_part="${1}"
+  local luks_part="${2}"
+  local luks_pwd="${3}"
+  local fde="${4}"
+  local fs="${5}"
+  # shellcheck disable=SC2034
+  local -n luks_part_uuid=$6
+  local -n data_part=$7
 
-  echo 'Wiping old signatures from partitions ...'
-  sudo wipefs "${BOOT_PART}" || return $?
-  sudo wipefs "${LUKS_PART}" || return $?
+  printf '%s\n' 'Wiping old signatures from partitions ...'
+  sudo wipefs --all "${boot_part}" || return $?
+  sudo wipefs --all "${luks_part}" || return $?
 
-  echo 'Formatting boot partition '"${BOOT_PART}"' ...'
-  sudo mkfs.fat -F32 "${BOOT_PART}" || return $?
+  printf '%s\n' "Formatting boot partition ${boot_part} ..."
+  sudo mkfs.fat -F32 "${boot_part}" || return $?
 
-  case "${FDE}" in
+  case "${fde}" in
   true)
-    # Note:
-    #  FDE: GRUB does support LUKS2 since this commit: https://git.savannah.gnu.org/cgit/grub.git/commit/?id=365e0cc3e7e44151c14dd29514c2f870b49f9755
-    #  -> Using "--type luks1" is no longer required.
-    echo 'Creating encrypted luks partition '"${LUKS_PART}"' ...'
-    printf '%s' "${LUKS_PWD}" | sudo cryptsetup luksFormat \
+    # FDE:
+    #   GRUB does support LUKS2 since this commit:
+    #   https://git.savannah.gnu.org/cgit/grub.git/commit/?id=365e0cc3e7e44151c14dd29514c2f870b49f9755
+    #   Using "--type luks1" is no longer required.
+    printf '%s\n' "Creating encrypted luks partition ${luks_part} ..."
+    printf '%s' "${luks_pwd}" | sudo cryptsetup luksFormat \
       --cipher aes-xts-plain64 --key-size 512 --hash sha512 \
-      --iter-time 10000 --use-random "${LUKS_PART}" || return $?
+      --iter-time 10000 --use-random "${luks_part}" || return $?
 
-    get_uuid "${LUKS_PART}" LUKS_PART_UUID || return $?
+    get_uuid "${luks_part}" luks_part_uuid || return $?
 
     local luks_name
-    luks_name=$(basename "${LUKS_PART}")
-    DATA_PART="/dev/mapper/${luks_name}"
+    luks_name="$(basename "${luks_part}")"
+    data_part="/dev/mapper/${luks_name}"
 
     # Open luks partition
-    printf '%s' "${LUKS_PWD}" | sudo cryptsetup luksOpen "${LUKS_PART}" "${luks_name}" || return $?
+    printf '%s' "${luks_pwd}" | sudo cryptsetup luksOpen "${luks_part}" "${luks_name}" || return $?
     ;;
   false)
-    DATA_PART="${LUKS_PART}"
+    data_part="${luks_part}"
     ;;
   *)
-    echo 'Invalid option: '"${FDE}"
+    printf '%s\n' "Invalid option: ${fde}"
     return 1
     ;;
   esac
 
-  echo 'Formatting the data partition '"${DATA_PART}"' ...'
-  case "${FS}" in
+  printf '%s\n' "Formatting the data partition ${data_part} ..."
+  case "${fs}" in
 	BTRFS)
-      sudo mkfs.btrfs "${DATA_PART}" || return $?
+      sudo mkfs.btrfs "${data_part}" || return $?
 		;;
 	EXT4)
-	    # archwiki -> Ext4#Enabling_metadata_checksums
-      sudo mkfs.ext4 -O metadata_csum "${DATA_PART}" || return $?
+      # https://wiki.archlinux.org/index.php/Ext4
+  	  # If the CPU supports SSE 4.2, make sure the crc32c_intel kernel module is loaded
+      sudo mkfs.ext4 -O metadata_csum "${data_part}" || return $?
 		;;
 	F2FS)
       # archwiki -> F2FS#Creating_a_F2FS_file_system
       # - requires f2fs-tools
       # - compression: "-O compression" and when mounting the filesystem, specify compress_algorithm=(lzo|lz4|zstd|lzo-rle)
-      sudo mkfs.f2fs -O extra_attr,inode_checksum,sb_checksum,compression "${DATA_PART}" || return $?
+      sudo mkfs.f2fs -O extra_attr,inode_checksum,sb_checksum,compression "${data_part}" || return $?
 		;;
 	*)
-		echo 'Filesystem '"${FS}"' is not yet supported!'
+		printf '%s\n' "Filesystem ${fs} is not yet supported!"
 		return 1
 		;;
   esac
diff --git a/lib/user-input.sh b/lib/user-input.sh
index 544d82f..2f08e5a 100644
--- a/lib/user-input.sh
+++ b/lib/user-input.sh
@@ -1,102 +1,84 @@
 function ask_user_if_empty {
-  # If variable with name $1 is empty, then ask for user input.
+  # If variable named $1 is empty, then ask for user input.
   #
-  # Only one line of user input is allowed.
-  # The input must not be empty.
+  # One line of user input is read.
+  # The user input must not be empty.
   #
   # arg $1: Name of variable to store user input
   # arg $2: Text to display (e.g. "Enter hostname:")
-  if [ "$#" -ne 2 ]; then
-    echo 'ask_user_if_empty requires two args!';
+  validate_args 2 "$@" || return $?
+  local -n user_input_ptr=$1
+  local display_text="${2}"
+
+  # If user_input_ptr is not empty, return
+  if [ -n "${user_input_ptr:-}" ]; then
+    return 0
+  fi
+  # Else, ask for user input!
+
+  printf '%s\n' "${display_text}"
+  read -r user_input_ptr || return $?
+
+  # User input must not be empty
+  if [ -z "${user_input_ptr}" ]; then
+    echo 'The input must not be empty!'
     return 1
   fi
-  for i in "$@"; do
-    if [ -z "${i}" ]; then
-      echo 'ask_user_if_empty: all given args must not be empty';
-      return 1;
-    fi
-  done
-
-  local -n ptr=$1 || return $?
-  if [ -z "${ptr}" ]; then
-    # If ptr has no value yet, ask user for input!
-    echo "${2}"
-    read -r ptr || return $?
-  fi
-
-  # Check string length to be greater than zero!
-  if [ "${#ptr}" -lt 1 ]; then
-    echo 'The input must not be empty!';
-    return 1;
-  fi
 }
 
 function single_choice_if_empty {
-  # If variable with name $1 is empty, then let user select one of the given options.
+  # If variable named $1 is empty,
+  # then let user select one of the given options.
   #
-  # arg $1: Name of variable to store the selected option
+  # arg $1: Name of variable to store the selected option-name
   # arg $2: Text to display
-  # arg $3: Name of variable with array of options to display (for each option there must be two entries in the array: Item and description)
-  if [ "$#" -ne 3 ]; then
-    echo 'single_choice_if_empty requires three args!';
+  # arg $3: Name of variable with array of options to display (for each option there must be two entries in the array: name and description)
+  validate_args 3 "$@" || return $?
+  local -n selected_option_ptr=$1
+  local display_text="${2}"
+  local -n menu_options_ptr=$3
+
+  # If selected_option_ptr is not empty, return.
+  if [ -n "${selected_option_ptr:-}" ]; then
+    return 0
+  fi
+  # Else, ask for user input!
+
+  selected_option_ptr=$(dialog --stdout --menu "${display_text}" 0 0 0 "${menu_options_ptr[@]}") || {
+    echo 'Error during menu selection!'
     return 1
-  fi
-  for i in "$@"; do
-    if [ -z "${i}" ]; then
-      echo 'single_choice_if_empty: all given args must not be empty';
-      return 1;
-    fi
-  done
-
-
-  local -n ptr=$1 || return $?
-  if [ -z "${ptr}" ]; then
-    # If ptr has no value yet, ask user for input!
-
-    local -n MENU_OPTIONS=$3 || return $?
-    ptr=$(dialog --stdout --menu "${2}" 0 0 0 "${MENU_OPTIONS[@]}") || {
-      echo 'Error during menu selection!'
-      exit 1
-    }
-    clear
-  fi
+  }
+  clear
 }
 
 function multi_choice_if_empty {
-  # If variable with name $1 is empty, then let user select one or more of the given options.
+  # If variable named $1 is empty,
+  # then let user select one or more of the given options.
   #
-  # arg $1: Name of variable to store array of selected options
+  # arg $1: Name of variable to store the selected option-names as array
   # arg $2: Text to display
-  # arg $3: Name of variable with array of options to display (for each option there must be three entries in the array: Item, description, on/off)
-    if [ "$#" -ne 3 ]; then
-    echo 'multi_choice_if_empty requires three args!';
+  # arg $3: Name of variable with array of options to display (for each option there must be three entries in the array: name, description, on/off)
+  validate_args 3 "$@" || return $?
+  local -n selected_option_ptr=$1
+  local display_text="${2}"
+  local -n menu_options_ptr=$3
+
+  # If selected_option_ptr is not empty, return.
+  if [ -n "${selected_option_ptr:-}" ]; then
+    return 0
+  fi
+  # Else, ask for user input!
+
+  selected_option_ptr=$(dialog --stdout --checklist "${display_text}" 0 0 0 "${menu_options_ptr[@]}") || {
+    echo 'Error during menu selection!'
     return 1
-  fi
-  for i in "$@"; do
-    if [ -z "${i}" ]; then
-      echo 'multi_choice_if_empty: all given args must not be empty';
-      return 1;
-    fi
-  done
+  }
+  clear
 
-
-  local -n ptr=$1 || return $?
-  if [ -z "${ptr}" ]; then
-    # If ptr has no value yet, ask user for input!
-
-    local -n MENU_OPTIONS=$3 || return $?
-    # shellcheck disable=SC2034 # Variable name used below.
-    TMP1=$(dialog --stdout --checklist "${2}" 0 0 0 "${MENU_OPTIONS[@]}") || {
-      echo 'Error during menu selection!'
-      exit 1
-    }
-    clear
-
-    # Result of dialog is a space separated list.
-    # Store this as an array.
-    # Without newline at last array element: https://unix.stackexchange.com/a/519917/315162
-    # readarray -d " " -t ptr < <(printf '%s' "$TMP1")
-    #
-    space_separated_to_array TMP1 "$1"
-  fi
+  # Result of dialog is a space separated list.
+  # Store this as an array.
+  # Without newline at last array element: https://unix.stackexchange.com/a/519917/315162
+  # readarray -d " " -t ptr < <(printf '%s' "selected_option_ptr")
+  #
+  space_separated_to_array selected_option_ptr selected_option_ptr || return $?
 }
diff --git a/lib/util.sh b/lib/util.sh
index 2dff9ce..508c9a8 100644
--- a/lib/util.sh
+++ b/lib/util.sh
@@ -1,83 +1,104 @@
 function join_by() {
   # Join array elements with character $1
   #
-  # arg $1: Delimiter
+  # arg $1: A single-character delimiter, e.g. ','
   # arg $2: Name of source array
   # arg $3: Variable name to store result
+  validate_args 3 "$@" || return $?
+  local delimiter="${1}"
+  local -n source_array_ptr=$2
+  local -n joined_ptr=$3
 
-  local -n ptr=$2  || return $?
-  local -n ptr2=$3 || return $?
-  ptr2=$(printf ',%s' "${ptr[@]}")
-  ptr2=${ptr2:1}
+  # https://stackoverflow.com/a/2317171
+  joined_ptr=$(printf "${delimiter}%s" "${source_array_ptr[@]}") || return $?
+  joined_ptr=${joined_ptr:1} || return $?
 }
 
 function newline_to_space() {
   # Replaces all newlines with spaces
   #
   # arg $1: Name of variable
+  validate_args 1 "$@" || return $?
+  local -n ptr=$1
 
-  local -n ptr=$1 || return $?
   # Replace newlines with spaces.
   # See bash string substitution: https://gist.github.com/JPvRiel/b279524d3e56229a896477cb8082a72b
-
-  # echo "replacing newlines in str: -->$ptr<--"
   ptr="${ptr//$'\n'/' '}"
-  # echo "new str is: -->$ptr<--"
 }
 
 function newline_separated_to_array() {
-  # Watch out for tailing newlines as these will get an empty array entry at the end.
+  # Watch out for tailing newlines as these result in additional elements "" at the end of the array.
   # $1 and $2 can be equal (if the result shall be written to the input variable).
   #
   # arg $1: Name of variable with newline separated list
   # arg $2: Name of array to store values into
+  validate_args 2 "$@" || return $?
+  local -n source_ptr=$1
+  local -n array1_ptr=$2
 
-  local -n ptr=$1  || return $?
-  local -n ptr2=$2 || return $?
-  # ptr newline separated list.
-  # Store this as array ptr2.
-  readarray -t ptr2 <<<"${ptr}"
+  # source_ptr is a newline separated list.
+  # Store this as array array1_ptr.
+  # shellcheck disable=SC2034
+  readarray -t array1_ptr <<<"${source_ptr}"
 }
 
 function space_separated_to_array() {
   # arg $1: Name of variable with space separated list
   # arg $2: Name of array to store values into
-
-  local -n ptr=$1  || return $?
+  validate_args 2 "$@" || return $?
+  local -n source_ptr=$1
   # shellcheck disable=SC2178
-  local -n ptr2=$2 || return $?
-  # ptr space separated list.
-  # Store this as array ptr2.
+  local -n array2_ptr=$2
+
+  # source_ptr space separated list.
+  # Store this as array array2_ptr.
   # Without newline at last array element: https://unix.stackexchange.com/a/519917/315162
-  readarray -d ' ' -t ptr2 < <(printf '%s' "${ptr}")
+  # shellcheck disable=SC2034
+  readarray -d ' ' -t array2_ptr < <(printf '%s' "${source_ptr}")
 }
 
 function get_cpu_vendor() {
+  # If $1 does already contain a known CPU vendor, nothing is done.
+  #
+  # Otherwise, we try to detect the CPU vendor and save it into $1.
+  #
+  # arg $1: Name of variable to store CPU vendor into.
+  #
   # @pre
-  #   CPU_VENDOR ("", "autodetect")
+  #   $1 ("amd", "intel", "none", *)
   # @post
-  #   CPU_VENDOR ("amd", "intel", "none", "")
+  #   $1 ("amd", "intel", "none")
+  validate_args 1 "$@" || return $?
+  local -n cpu_vendor_ptr=$1
 
-  if [[ -z "${CPU_VENDOR}" ]] || [[ "${CPU_VENDOR}" == 'autodetect' ]]; then
+  # Check if variable does already contain known CPU vendor.
+  case "${cpu_vendor_ptr}" in
+    amd|intel|none)
+      return 0
+      ;;
+    *)
+      :
+      ;;
+  esac
 
-    # If run virtual environment (e.g. VirtualBox) then no CPU microcode is required.
-    if grep '^flags.*hypervisor' /proc/cpuinfo >/dev/null; then
-      echo 'Detected virtual environment.'
-      CPU_VENDOR='none'
+  # If in virtual environment (e.g. VirtualBox), then no CPU microcode is required.
+  if grep --quiet '^flags.*hypervisor' /proc/cpuinfo; then
+    echo 'Detected virtual environment.'
+    cpu_vendor_ptr='none'
+    return 0
+  fi
 
-    else
-      local vendor_id
-      vendor_id=$(grep vendor_id /proc/cpuinfo | head -1 | sed 's|vendor_id\s*:\s*||')
-
-      if [ "${vendor_id}" = 'AuthenticAMD' ]; then
-        CPU_VENDOR='amd'
-      elif [ "${vendor_id}" = 'GenuineIntel' ]; then
-        CPU_VENDOR='intel'
-      else
-        echo 'Unknown CPU vendor'
-        return 1
-      fi
-    fi
+  local vendor_id
+  vendor_id="$(grep vendor_id /proc/cpuinfo | head -1 | sed 's|vendor_id\s*:\s*||')"
 
+  if [ "${vendor_id}" = 'AuthenticAMD' ]; then
+    cpu_vendor_ptr='amd'
+    return 0
+  elif [ "${vendor_id}" = 'GenuineIntel' ]; then
+    cpu_vendor_ptr='intel'
+    return 0
+  else
+    echo 'Unknown CPU vendor'
+    return 1
   fi
 }
diff --git a/lib/validate-args.sh b/lib/validate-args.sh
new file mode 100644
index 0000000..54e8bcc
--- /dev/null
+++ b/lib/validate-args.sh
@@ -0,0 +1,15 @@
+function validate_args(){
+  local num_args="${1}"
+  shift
+
+  if [ "$#" -ne "${num_args}" ]; then
+    printf '%s\n' "ERROR: ${num_args} arguments required"
+    return 1
+  fi
+  for i in "$@"; do
+    if [ -z "${i}" ]; then
+      printf '%s\n' 'ERROR: All given args must not be empty'
+      return 1
+    fi
+  done
+}
diff --git a/name-reference-test.sh b/name-reference-test.sh
deleted file mode 100644
index 86d2f6b..0000000
--- a/name-reference-test.sh
+++ /dev/null
@@ -1,39 +0,0 @@
-#!/bin/bash
-# source: https://stackoverflow.com/a/52678279/6334421
-
-# A variable can be assigned the nameref attribute using the -n option
-# to the declare or local builtin commands (see Bash Builtins) to create
-# a nameref, or a reference to another variable. This allows variables to
-# be manipulated indirectly.
-
-function text_input {
-  # If variable of name $1 is zero, then ask user for input.
-  # Only one line user input is allowed.
-  # User input must not be empty.
-  #
-  # $1: variable name to store input to
-  # $2: text to display (e.g. "Enter hostname:")
-  if [ -z "${1}" ] || [ -z "${2}" ]; then
-    echo 'text_input requires two args!';
-    return 1
-  fi
-
-  local -n ptr=$1 || return $?
-  if [ -z "${ptr}" ]; then
-    echo "${2}"
-    read -r ptr || return $?
-  fi
-
-  # check string length to be greater than zero!
-  if [ "${#ptr}" -lt 1 ]; then
-    echo 'text_input must not be empty!';
-    return 1;
-  fi
-}
-
-text_input foo 'Enter something funny:'
-echo "Input: ${foo}"
-
-bar=''
-text_input bar 'Enter something even funnier:'
-echo "Input: ${bar}"