Refactor user runtime hooks installation and processing

- Add new hook points: load-key.d and boot-sel.d

- All hooks are installed in hook-point-specific subdirectories of
  /libexec/hooks instead of in the top-level /libexec

- User hooks are recognized in level-specific subdirectories of a
  zfsbootmenu_hook_root defined for dracut or mkinitcpio

- Deprecate zfsbootmenu_{early_setup,setup,teardown} variables

- Take advantage of zfsbootmenu_hook_root to simplify hooks in container
  builds via zbm-builder.sh

- Simplify zbm.hookdir overrides

Closes: #477.

Author: ahesford

docs/guides/general/container-building.rst

@@ -133,23 +133,9 @@ The default behavior of ``zbm-builder.sh`` will:
 Custom ZFSBootMenu Hooks
 ~~~~~~~~~~~~~~~~~~~~~~~~
 
-ZFSBootMenu supports :ref:`custom hooks <zbm-dracut-options>` in three stages:
-
-1. ``early_setup`` hooks run after the ``zfs`` kernel driver has been loaded, but before ZFSBootMenu attempts to import
-   any pools.
-2. ``setup`` hooks run after pools are imported, right before ZFSBootMenu will either boot a default environment or
-   present a menu.
-3. ``teardown`` hooks run immediately before ZFSBootMenu will ``kexec`` the kernel for the selected environment.
-
-When ``zbm-builder.sh`` runs, it will identify custom hooks as executable files in the respective subdirectories of its
-build directory:
-
-1. ``hooks.early_setup.d``
-2. ``hooks.setup.d``
-3. ``hooks.teardown.d``
-
-For each hook directory that contains at least one executable file, ``zbm-builder.sh`` will write custom configuration
-snippets for ``dracut`` and ``mkinitcpio`` that will include these files in the output images.
+ZFSBootMenu supports :ref:`custom hooks <zbm-dracut-options>` in several stages. When ``zbm-builder.sh`` runs, it will
+configure the subdirectory ``hooks`` of the build directory, if it exists, as the value of ``zfsbootmenu_hook_root`` to
+allow custom hooks to be included in ZFSBootMenu images.
 
 Fully Customizing Images
 ~~~~~~~~~~~~~~~~~~~~~~~~

docs/man/dist/man7/zfsbootmenu.7

@@ -30,6 +30,7 @@ installkernel() {
 
 install() {
   : "${zfsbootmenu_module_root:=/usr/share/zfsbootmenu}"
+  : "${zfsbootmenu_hook_root:=/etc/zfsbootmenu/hooks}"
 
   # shellcheck disable=SC1091
   if ! source "${zfsbootmenu_module_root}/install-helpers.sh" ; then

docs/man/zfsbootmenu.7.rst

@@ -24,14 +24,9 @@ HOOKS=(base udev autodetect modconf block filesystems keyboard)
 #     dracut.conf.d
 #     mkinitcpio.conf.d
 #
-# of the build directory for any hook found in the subdirectories
-#
-#     hooks.early_setup.d
-#     hooks.setup.d
-#     hooks.teardown.d
-#
-# of the same build directory. Support for mkinitcpio.conf.d mimics similar
-# support for dracut.conf.d built directly into dracut.
+# of the build directory for any hooks found in the hooks subdirectory of the
+# build directory. Support for mkinitcpio.conf.d mimics similar support for
+# dracut.conf.d built directly into dracut.
 #
 # Note that, inside the container, the build directory will be mounted at
 # /build, so reference those paths here.

dracut/module-setup.sh

@@ -75,25 +75,8 @@ HOOKS=(base udev autodetect modconf block filesystems keyboard zfsbootmenu)
 # tested and may break some (non-essential) ZFSBootMenu features.
 #zfsbootmenu_miser="no"
 
-# zfsbootmenu_early_setup, zfsbootmenu_setup, zfsbootmenu_teardown
+# zfsbootmenu_hook_root
 # ZFSBootMenu supports user-provided hooks that may be run at various points in
-# the boot process. Set each of these variables to an array of executable files
-# that should be installed as user hooks in the provided image. Files that are
-# not executable will be ignored. See the zfsbootmenu(7) manual page for more
-# details about these hooks.
-#
-# 'zfsbootmenu_early_setup' hooks are run after ZFS modules are loaded, but
-# before ZFSBootMenu attempts to import any pools. Hooks here, for example, can
-# unlock LUKS volumes or otherwise manage devices that must be made available
-# before a pool can be recognized.
-#
-# 'zfsbootmenu_setup' hooks are run after pools are imported and right before
-# the menu is presented.
-#
-# 'zfsbootmenu_teardown' hooks are run immediately before a chosen boot
-# environment is about to be launched. Any writable ZFS pools will have been
-# exported, but read-only pools will generally still be available.
-#
-#zfsbootmenu_early_setup=()
-#zfsbootmenu_setup=()
-#zfsbootmenu_teardown=()
+# the boot process. Set zfsbootmenu_hook_root to the path of the hooks tree
+# that includes a subdirectory for each hook point.
+#zfsbootmenu_hook_root="/etc/zfsbootmenu/hooks"

etc/zbm-builder/mkinitcpio.conf

@@ -114,9 +114,10 @@ create_zbm_entrypoint() {
 
 
 build() {
-    local hooks relative _file
+    local _file
 
     : "${zfsbootmenu_module_root:=/usr/share/zfsbootmenu}"
+    : "${zfsbootmenu_hook_root:=/etc/zfsbootmenu/hooks}"
 
     # shellcheck disable=SC1091
     source "${zfsbootmenu_module_root}/install-helpers.sh" || exit 1

etc/zfsbootmenu/mkinitcpio.conf

@@ -242,7 +242,6 @@ if [ -n "${DISPLAY_TYPE}" ]; then
   # Add release hooks, supported only under Dracut
   if ((DRACUT)); then
     cat <<-EOF >> "${TESTDIR}/dracut.conf.d/testing.conf"
-	zfsbootmenu_early_setup+=" $( realpath -e ../contrib )/10-console-init.sh "
 	zfsbootmenu_early_setup+=" $( realpath -e ../contrib )/20-console-autosize.sh "
 	EOF
   fi

initcpio/install/zfsbootmenu

@@ -239,32 +239,17 @@ if ! [ -r "${BUILD_DIRECTORY}"/config.yaml ]; then
 fi
 
 # Try to include ZBM hooks in the images by default
-for stage in early_setup setup teardown; do
-  [ -d "${BUILD_DIRECTORY}/hooks.${stage}.d" ] || continue
-
-  # Only executable hooks are added to the image
-  hooks=()
-  for f in "${BUILD_DIRECTORY}/hooks.${stage}.d"/*; do
-    [ -x "${f}" ] || continue
-    hooks+=( "/build/hooks.${stage}.d/${f##*/}" )
-  done
-
-  [ "${#hooks[@]}" -gt 0 ] || continue
-
-  hconf="zbm-builder.${stage}.conf"
-
+if [ -d "${BUILD_DIRECTORY}/hooks" ]; then
   # Write a dracut configuration snippet
   mkdir -p "${BUILD_DIRECTORY}/dracut.conf.d"
-  echo "zfsbootmenu_${stage}+=\" ${hooks[*]} \"" > "${BUILD_DIRECTORY}/dracut.conf.d/${hconf}"
+  echo "zfsbootmenu_hook_root=/build/hooks" \
+    > "${BUILD_DIRECTORY}/dracut.conf.d/user_hooks.conf"
 
   # Write a mkinitcpio configuration snippet
   mkdir -p "${BUILD_DIRECTORY}/mkinitcpio.conf.d"
-  echo "zfsbootmenu_${stage}=(" > "${BUILD_DIRECTORY}/mkinitcpio.conf.d/${hconf}"
-  for hook in "${hooks[@]}"; do
-    echo "  \"${hook}\"" >> "${BUILD_DIRECTORY}/mkinitcpio.conf.d/${hconf}"
-  done
-  echo ")" >> "${BUILD_DIRECTORY}/mkinitcpio.conf.d/${hconf}"
-done
+  echo "zfsbootmenu_hook_root=/build/hooks" \
+    > "${BUILD_DIRECTORY}/mkinitcpio.conf.d/user_hooks.conf"
+fi
 
 # Make `/build` the working directory so relative paths in configs make sense
 exec "${PODMAN}" run \