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[Merge] ~sjg1/curtin:boot2 into curtin:master

 

Simon Glass has proposed merging ~sjg1/curtin:boot2 into curtin:master.

Commit message:
Curtin currently assumes that grub is used as the bootloader.

Generalise the schema to support multiple bootloaders

TBD: Add extlinux support

DO NOT SQUASH

Requested reviews:
  curtin developers (curtin-dev)

For more details, see:
https://code.launchpad.net/~sjg1/curtin/+git/curtin/+merge/480712

The idea here is to allow MAAS to set up RISC-V clients without needing grub. They can use extlinux instead, meaning that U-Boot is enough to handle the full boot.

I have made the schema changes but I need to figure out how to get the device and mount point for the root and boot devices.
-- 
Your team curtin developers is requested to review the proposed merge of ~sjg1/curtin:boot2 into curtin:master.
diff --git a/.gitignore b/.gitignore
index 8f343e7..1c6bd5e 100644
--- a/.gitignore
+++ b/.gitignore
@@ -3,3 +3,4 @@ __pycache__
 .tox
 .coverage
 curtin.egg-info/
+doc/_build
diff --git a/curtin/commands/curthooks.py b/curtin/commands/curthooks.py
index 82ebcab..9706494 100644
--- a/curtin/commands/curthooks.py
+++ b/curtin/commands/curthooks.py
@@ -32,6 +32,7 @@ from curtin.net import deps as ndeps
 from curtin.reporter import events
 from curtin.commands import apply_net, apt_config
 from curtin.commands.install_grub import install_grub
+from curtin.commands.install_extlinux import install_extlinux
 from curtin.url_helper import get_maas_version
 
 from . import populate_one_subcmd
@@ -439,7 +440,7 @@ def install_kernel(cfg, target):
                          " System may not boot.", package)
 
 
-def uefi_remove_old_loaders(grubcfg: config.GrubConfig, target: str):
+def uefi_remove_old_loaders(bootcfg: config.BootCfg, target: str):
     """Removes the old UEFI loaders from efibootmgr."""
     efi_state = util.get_efibootmgr(target)
 
@@ -457,7 +458,7 @@ def uefi_remove_old_loaders(grubcfg: config.GrubConfig, target: str):
     if not old_efi_entries:
         return
 
-    if grubcfg.remove_old_uefi_loaders:
+    if bootcfg.remove_old_uefi_loaders:
         with util.ChrootableTarget(target) as in_chroot:
             for number, entry in old_efi_entries.items():
                 LOG.debug("removing old UEFI entry: %s", entry.name)
@@ -532,7 +533,7 @@ def _reorder_new_entry(
 
 
 def uefi_reorder_loaders(
-        grubcfg: config.GrubConfig,
+        bootcfg: config.BootCfg,
         target: str,
         efi_orig_state: util.EFIBootState,
         variant: str,
@@ -548,7 +549,7 @@ def uefi_reorder_loaders(
     is installed after the the previous first entry (before we installed grub).
 
     """
-    if not grubcfg.reorder_uefi:
+    if not bootcfg.reorder_uefi:
         LOG.debug("Skipped reordering of UEFI boot methods.")
         LOG.debug("Currently booted UEFI loader might no longer boot.")
         return
@@ -557,7 +558,7 @@ def uefi_reorder_loaders(
     LOG.debug('UEFI efibootmgr output after install:\n%s', efi_state)
     new_boot_order = None
 
-    if efi_state.current and not grubcfg.reorder_uefi_force_fallback:
+    if efi_state.current and not bootcfg.reorder_uefi_force_fallback:
         boot_order = list(efi_state.order)
         if efi_state.current in boot_order:
             boot_order.remove(efi_state.current)
@@ -566,7 +567,7 @@ def uefi_reorder_loaders(
             "Setting currently booted %s as the first UEFI loader.",
             efi_state.current)
     else:
-        if grubcfg.reorder_uefi_force_fallback:
+        if bootcfg.reorder_uefi_force_fallback:
             reason = "config 'reorder_uefi_force_fallback' is True"
         else:
             reason = "missing 'BootCurrent' value"
@@ -592,10 +593,10 @@ def uefi_reorder_loaders(
 
 
 def uefi_remove_duplicate_entries(
-        grubcfg: config.GrubConfig,
+        bootcfg: config.BootCfg,
         target: str,
         ) -> None:
-    if not grubcfg.remove_duplicate_entries:
+    if not bootcfg.remove_duplicate_entries:
         LOG.debug("Skipped removing duplicate UEFI boot entries per config.")
         return
 
@@ -752,13 +753,7 @@ def setup_grub(
     from curtin.commands.block_meta import (extract_storage_ordered_dict,
                                             get_path_to_storage_volume)
 
-    grubcfg_d = cfg.get('grub', {})
-
-    # copy legacy top level name
-    if 'grub_install_devices' in cfg and 'install_devices' not in grubcfg_d:
-        grubcfg_d['install_devices'] = cfg['grub_install_devices']
-
-    grubcfg = config.fromdict(config.GrubConfig, grubcfg_d)
+    bootcfg = config.fromdict(config.BootCfg, cfg.get('boot', {}))
 
     LOG.debug("setup grub on target %s", target)
     # if there is storage config, look for devices tagged with 'grub_device'
@@ -784,16 +779,16 @@ def setup_grub(
                     get_path_to_storage_volume(item_id, storage_cfg_odict))
 
         if len(storage_grub_devices) > 0:
-            if grubcfg.install_devices and \
-               grubcfg.install_devices is not grubcfg.install_devices_default:
+            if bootcfg.install_devices and \
+               bootcfg.install_devices is not bootcfg.install_devices_default:
                 LOG.warn("Storage Config grub device config takes precedence "
                          "over grub 'install_devices' value, ignoring: %s",
-                         grubcfg['install_devices'])
-            grubcfg.install_devices = storage_grub_devices
+                         bootcfg['install_devices'])
+            bootcfg.install_devices = storage_grub_devices
 
-    LOG.debug("install_devices: %s", grubcfg.install_devices)
-    if grubcfg.install_devices is not grubcfg.install_devices_default:
-        instdevs = grubcfg.install_devices
+    LOG.debug("install_devices: %s", bootcfg.install_devices)
+    if bootcfg.install_devices is not bootcfg.install_devices_default:
+        instdevs = bootcfg.install_devices
         if instdevs is None:
             LOG.debug("grub installation disabled by config")
     else:
@@ -843,16 +838,70 @@ def setup_grub(
     else:
         instdevs = ["none"]
 
-    update_nvram = grubcfg.update_nvram
+    update_nvram = bootcfg.update_nvram
     if uefi_bootable and update_nvram:
         efi_orig_state = util.get_efibootmgr(target)
-        uefi_remove_old_loaders(grubcfg, target)
+        uefi_remove_old_loaders(bootcfg, target)
 
-    install_grub(instdevs, target, uefi=uefi_bootable, grubcfg=grubcfg)
+    install_grub(instdevs, target, uefi=uefi_bootable, bootcfg=bootcfg)
 
     if uefi_bootable and update_nvram:
-        uefi_reorder_loaders(grubcfg, target, efi_orig_state, variant)
-        uefi_remove_duplicate_entries(grubcfg, target)
+        uefi_reorder_loaders(bootcfg, target, efi_orig_state, variant)
+        uefi_remove_duplicate_entries(bootcfg, target)
+
+
+def translate_old_grub_schema(cfg):
+    """Translate the old top-level 'grub' configure to the new 'boot' one"""
+    grub_cfg = cfg.get('grub', {})
+
+    # Use the 'boot' key, if present
+    if 'boot' in cfg:
+        if grub_cfg:
+            raise ValueError("Configuration has both 'grub' and 'boot' keys")
+        return
+
+    # copy legacy top level name
+    if 'grub_install_devices' in cfg and 'install_devices' not in cfg:
+        grub_cfg['install_devices'] = cfg['grub_install_devices']
+
+    if 'grub' in cfg:
+        del cfg['grub']
+
+    # Create a bootloaders list with 'grub', which is implied in the old config
+    grub_cfg['bootloaders'] = ['grub']
+
+    cfg['boot'] = grub_cfg
+
+
+def setup_boot(
+        cfg: dict,
+        target: str,
+        machine: str,
+        stack_prefix: str,
+        osfamily: str,
+        variant: str,
+        ) -> None:
+    translate_old_grub_schema(cfg)
+
+    boot_cfg = cfg['boot']
+    bootloaders = boot_cfg['bootloaders']
+
+    # For now we have a hard-coded mechanism to determine whether grub should
+    # be installed or not. Even if the grub info is present in the config, we
+    # check the machine to decide whether or not to install it.
+    if 'grub' in bootloaders and uses_grub(machine):
+        with events.ReportEventStack(
+                name=stack_prefix + '/install-grub',
+                reporting_enabled=True, level="INFO",
+                description="installing grub to target devices"):
+            setup_grub(cfg, target, osfamily=osfamily, variant=variant)
+
+    if 'extlinux' in bootloaders:
+        with events.ReportEventStack(
+                name=stack_prefix + '/install-extlinux',
+                reporting_enabled=True, level="INFO",
+                description="installing extlinux to target devices"):
+            install_extlinux(cfg, target, osfamily=osfamily, variant=variant)
 
 
 def update_initramfs(target=None, all_kernels=False):
@@ -898,12 +947,7 @@ def update_initramfs(target=None, all_kernels=False):
         # if the initrd file exists, then we only need to invoke
         # update-initramfs's -u (update) method.  If the file does
         # not exist, then we need to run the -c (create) method.
-        for kernel in sorted(glob.glob(boot + '/vmlinu*-*')):
-            kfile = os.path.basename(kernel)
-            # handle vmlinux or vmlinuz
-            kprefix = kfile.split('-')[0]
-            version = kfile.replace(kprefix + '-', '')
-            initrd = kernel.replace(kprefix, 'initrd.img')
+        for kfile, initrd, version in paths.get_kernel_list(target):
             # -u == update, -c == create
             mode = '-u' if os.path.exists(initrd) else '-c'
             cmd = ['update-initramfs', mode, '-k', version]
@@ -926,7 +970,7 @@ def update_initramfs(target=None, all_kernels=False):
     else:
         # Curtin only knows update-initramfs (provided by initramfs-tools) and
         # dracut.
-        if not glob.glob(boot + '/vmlinu*-*'):
+        if not list(paths.get_kernel_list(target)):
             LOG.debug("neither update-initramfs or dracut found in target %s"
                       " but there is no initramfs to generate, so ignoring",
                       target)
@@ -2051,13 +2095,8 @@ def builtin_curthooks(cfg, target, state):
             reporting_enabled=True, level="INFO",
             description="configuring target system bootloader"):
 
-        if uses_grub(machine):
-            with events.ReportEventStack(
-                    name=stack_prefix + '/install-grub',
-                    reporting_enabled=True, level="INFO",
-                    description="installing grub to target devices"):
-                setup_grub(cfg, target, osfamily=osfamily,
-                           variant=distro_info.variant)
+        setup_boot(cfg, target, machine, stack_prefix, osfamily=osfamily,
+                   variant=distro_info.variant)
 
     # Copy information from installation media
     with events.ReportEventStack(
diff --git a/curtin/commands/install_extlinux.py b/curtin/commands/install_extlinux.py
new file mode 100644
index 0000000..8e378c2
--- /dev/null
+++ b/curtin/commands/install_extlinux.py
@@ -0,0 +1,85 @@
+# This file is part of curtin. See LICENSE file for copyright and license info.
+
+"""This loosely follows the u-boot-update script in the u-boot-menu package"""
+
+import io
+import os
+
+from curtin import config
+from curtin import paths
+from curtin.log import LOG
+
+EXTLINUX_DIR = '/boot/extlinux'
+
+
+def build_content(target: str, bootcfg: config.BootCfg):
+    """Build the content of the extlinux.conf file
+
+    For now this only supports x86, since it does not handle the 'fdt' option.
+    Rather than add that, the plan is to use a FIT (Flat Image Tree) which can
+    handle FDT selection automatically. This should avoid the complexity
+    associated with fdt and fdtdir options.
+
+    We assume that the boot/ directory is in the root partition, rather than
+    being in a separate partition. TBD.
+    """
+    def get_entry(label, params, menu_label_append=''):
+        return f'''\
+label {label}
+\tmenu label {menu_label} {version}{menu_label_append}
+\tlinux /{kernel_path}
+\tinitrd /{initrd_path}
+\tappend root={root} {params}'''
+
+    buf = io.StringIO()
+    params = 'ro quiet'
+    alternatives = ['default', 'recovery']
+    menu_label = 'Ubuntu 22.04.5 LTS'
+    root = '/dev/mapper/vgubuntu-root'  # TODO
+
+    # For the recovery option, remove 'quiet' and add 'single'
+    without_quiet = filter(lambda word: word != 'quiet', params.split())
+    rec_params = ' '.join(list(without_quiet) + ['single'])
+
+    print(f'''\
+## {EXTLINUX_DIR}/extlinux.conf
+##
+## IMPORTANT WARNING
+##
+## The configuration of this file is generated automatically.
+## Do not edit this file manually, use: u-boot-update
+
+default l0
+menu title U-Boot menu
+prompt 0
+timeout 50''', file=buf)
+    for seq, (kernel_path, full_initrd_path, version) in enumerate(
+            paths.get_kernel_list(target)):
+        LOG.debug('P: Writing config for %s...', kernel_path)
+        initrd_path = os.path.basename(full_initrd_path)
+        print(file=buf)
+        print(file=buf)
+        print(get_entry(f'l{seq}', params), file=buf)
+
+        if 'recovery' in alternatives:
+            print(file=buf)
+            print(get_entry(f'l{seq}r', rec_params, ' (rescue target)'),
+                  file=buf)
+
+    return buf.getvalue()
+
+
+def install_extlinux(
+        target: str,
+        bootcfg: config.BootCfg,
+        ):
+    """Install extlinux to the target chroot.
+
+    :param: target: A string specifying the path to the chroot mountpoint.
+    :param: bootcfg: An config dict with grub config options.
+    """
+    content = build_content(target, bootcfg)
+    extlinux_path = paths.target_path(target, '/boot/extlinux')
+    os.makedirs(extlinux_path, exist_ok=True)
+    with open(extlinux_path + '/extlinux.conf', 'w', encoding='utf-8') as outf:
+        outf.write(content)
diff --git a/curtin/commands/install_grub.py b/curtin/commands/install_grub.py
index 6d1d59e..e6fa1ef 100644
--- a/curtin/commands/install_grub.py
+++ b/curtin/commands/install_grub.py
@@ -2,7 +2,6 @@ import os
 import re
 import platform
 import shutil
-import sys
 from typing import List, Optional
 
 from curtin import block
@@ -11,8 +10,6 @@ from curtin import distro
 from curtin import util
 from curtin.log import LOG
 from curtin.paths import target_path
-from curtin.reporter import events
-from . import populate_one_subcmd
 
 CMD_ARGUMENTS = (
     ((('-t', '--target'),
@@ -209,15 +206,15 @@ def replace_grub_cmdline_linux_default(target, new_args):
 
 def write_grub_config(
         target: str,
-        grubcfg: config.GrubConfig,
+        bootcfg: config.BootCfg,
         grub_conf: str,
         new_params: str,
         ) -> None:
-    replace_default = grubcfg.replace_linux_default
+    replace_default = bootcfg.replace_linux_default
     if replace_default:
         replace_grub_cmdline_linux_default(target, new_params)
 
-    probe_os = grubcfg.probe_additional_os
+    probe_os = bootcfg.probe_additional_os
     if not probe_os:
         probe_content = [
             ('# Curtin disable grub os prober that might find other '
@@ -228,7 +225,7 @@ def write_grub_config(
                         "\n".join(probe_content), omode='a+')
 
     # if terminal is present in config, but unset, then don't
-    grub_terminal = grubcfg.terminal
+    grub_terminal = bootcfg.terminal
     if not grub_terminal.lower() == "unmodified":
         terminal_content = [
             '# Curtin configured GRUB_TERMINAL value',
@@ -402,7 +399,7 @@ def install_grub(
         devices: List[str],
         target: str,
         *,
-        grubcfg: config.GrubConfig,
+        bootcfg: config.BootCfg,
         uefi: Optional[bool] = None,
         ):
     """Install grub to devices inside target chroot.
@@ -411,7 +408,7 @@ def install_grub(
     :param: target: A string specifying the path to the chroot mountpoint.
     :param: uefi: A boolean set to True if system is UEFI bootable otherwise
                   False.
-    :param: grubcfg: An config dict with grub config options.
+    :param: bootcfg: An config dict with grub config options.
     """
 
     if not devices:
@@ -421,8 +418,8 @@ def install_grub(
         raise ValueError("Invalid parameter 'target': %s" % target)
 
     LOG.debug("installing grub to target=%s devices=%s [replace_defaults=%s]",
-              target, devices, grubcfg.replace_linux_default)
-    update_nvram = grubcfg.update_nvram
+              target, devices, bootcfg.replace_linux_default)
+    update_nvram = bootcfg.update_nvram
     distroinfo = distro.get_distroinfo(target=target)
     target_arch = distro.get_architecture(target=target)
     rhel_ver = (distro.rpm_get_dist_id(target)
@@ -435,7 +432,7 @@ def install_grub(
     grub_conf = get_grub_config_file(target, distroinfo.family)
     new_params = get_carryover_params(distroinfo)
     prepare_grub_dir(target, grub_conf)
-    write_grub_config(target, grubcfg, grub_conf, new_params)
+    write_grub_config(target, bootcfg, grub_conf, new_params)
     grub_cmd = get_grub_install_command(uefi, distroinfo, target)
     if uefi:
         install_cmds, post_cmds = gen_uefi_install_commands(
@@ -453,35 +450,4 @@ def install_grub(
         for cmd in install_cmds + post_cmds:
             in_chroot.subp(cmd, env=env, capture=True)
 
-
-def install_grub_main(args):
-    state = util.load_command_environment()
-
-    if args.target is not None:
-        target = args.target
-    else:
-        target = state['target']
-
-    if target is None:
-        sys.stderr.write("Unable to find target.  "
-                         "Use --target or set TARGET_MOUNT_POINT\n")
-        sys.exit(2)
-
-    cfg = config.load_command_config(args, state)
-    stack_prefix = state.get('report_stack_prefix', '')
-    uefi = util.is_uefi_bootable()
-
-    util.EFIVarFSBug.apply_workaround_if_affected()
-
-    grubcfg = config.fromdict(config.GrubConfig, cfg.get('grub'))
-    with events.ReportEventStack(
-            name=stack_prefix, reporting_enabled=True, level="INFO",
-            description="Installing grub to target devices"):
-        install_grub(args.devices, target, uefi=uefi, grubcfg=grubcfg)
-    sys.exit(0)
-
-
-def POPULATE_SUBCMD(parser):
-    populate_one_subcmd(parser, CMD_ARGUMENTS, install_grub_main)
-
 # vi: ts=4 expandtab syntax=python
diff --git a/curtin/config.py b/curtin/config.py
index e9f6516..da9e486 100644
--- a/curtin/config.py
+++ b/curtin/config.py
@@ -136,8 +136,21 @@ def _convert_install_devices(value):
     return value
 
 
+def _check_bootloaders(inst, attr, vals):
+    if not isinstance(vals, list):
+        raise ValueError(f'bootloaders must be a list: {vals}')
+    if not vals:
+        raise ValueError(f'Empty bootloaders list: {vals}')
+    if len(vals) != len(set(vals)):
+        raise ValueError(f'bootloaders list contains duplicates: {vals}')
+    for val in vals:
+        if val not in ['grub', 'extlinux']:
+            raise ValueError(f'Unknown bootloader {val}: {vals}')
+
+
 @attr.s(auto_attribs=True)
-class GrubConfig:
+class BootCfg:
+    bootloaders: typing.List[str] = attr.ib(validator=_check_bootloaders)
     install_devices_default = object()
     install_devices: typing.Optional[typing.List[str]] = attr.ib(
         converter=_convert_install_devices, default=install_devices_default)
diff --git a/curtin/paths.py b/curtin/paths.py
index 064b060..98aa648 100644
--- a/curtin/paths.py
+++ b/curtin/paths.py
@@ -1,5 +1,8 @@
 # This file is part of curtin. See LICENSE file for copyright and license info.
+import glob
 import os
+from packaging import version
+import re
 
 try:
     string_types = (basestring,)
@@ -31,4 +34,38 @@ def target_path(target, path=None):
 
     return os.path.join(target, path)
 
+
+def kernel_parse(fname):
+    """Function to extract version to use for sorting"""
+    m = re.search(r".*/vmlinu.-([\d.-]+)-.*", fname)
+    if not m:
+        raise ValueError(f"Cannot extract version from '{fname}'")
+    return version.parse(m.group(1))
+
+
+def get_kernel_list(target, full_initrd_path=True):
+    """yields [kernel filename, initrd path, version] for each kernel in target
+
+    For example:
+       ('vmlinuz-6.8.0-48-generic', '/boot/initrd.img-6.8.0-48-generic',
+        '6.8.0-48-generic')
+
+    If full_initrd_path is False, then only the basename of initrd is returned
+    """
+    root_path = target_path(target)
+    boot = target_path(root_path, 'boot')
+
+    for kernel in sorted(glob.glob(boot + '/vmlinu*-*'), key=kernel_parse,
+                         reverse=True):
+        kfile = os.path.basename(kernel)
+
+        # handle vmlinux or vmlinuz
+        kprefix = kfile.split('-')[0]
+        vers = kfile.replace(kprefix + '-', '')
+        initrd = kernel.replace(kprefix, 'initrd.img')
+        if not full_initrd_path:
+            initrd = os.path.basename(initrd)
+        yield kfile, initrd, vers
+
+
 # vi: ts=4 expandtab syntax=python
diff --git a/doc/topics/config.rst b/doc/topics/config.rst
index 4fbcc5a..fde668b 100644
--- a/doc/topics/config.rst
+++ b/doc/topics/config.rst
@@ -10,10 +10,14 @@ Configuration options
 ---------------------
 Curtin's top level config keys are as follows:
 
+.. contents::
+    :depth: 1
+    :local:
 
 - apt_mirrors (``apt_mirrors``)
 - apt_proxy (``apt_proxy``)
 - block-meta (``block``)
+- boot (``boot``)
 - curthooks (``curthooks``)
 - debconf_selections (``debconf_selections``)
 - disable_overlayroot (``disable_overlayroot``)
@@ -112,81 +116,65 @@ Specify the filesystem label on the boot partition.
           label: my-boot-partition
 
 
-curthooks
-~~~~~~~~~
-Configure how Curtin determines what :ref:`curthooks` to run during the installation
-process.
-
-**mode**: *<['auto', 'builtin', 'target']>*
-
-The default mode is ``auto``.
-
-In ``auto`` mode, curtin will execute curthooks within the image if present.
-For images without curthooks inside, curtin will execute its built-in hooks.
-
-Currently the built-in curthooks support the following OS families:
-
-- Ubuntu
-- Centos
-
-When specifying ``builtin``, curtin will only run the curthooks present in
-Curtin ignoring any curthooks that may be present in the target operating
-system.
-
-When specifying ``target``, curtin will attempt run the curthooks in the target
-operating system.  If the target does NOT contain any curthooks, then the
-built-in curthooks will be run instead.
-
-Any errors during execution of curthooks (built-in or target) will fail the
-installation.
-
-**Example**::
+boot
+~~~~
 
-  # ignore any target curthooks
-  curthooks:
-    mode: builtin
+Configures which bootloader(s) Curtin installs and some associated options.
+This is a list, which can contain up to two options: `grub` and `extlinux`.
 
-  # Only run target curthooks, fall back to built-in
-  curthooks:
-    mode: target
+Two bootloaders are available:
 
+- `GRUB <https://www.gnu.org/software/grub/>`_ (GRand Unified Bootloader)
+  installs itself on one or more block devices and takes care of booting.
+  Typically grub is built as an EFI application. Curtin controls aspects of
+  grub's configuration-file (/boot/grub/grub.cfg) which tells grub which OS
+  options to present to the user.
 
-debconf_selections
-~~~~~~~~~~~~~~~~~~
-Curtin will update the target with debconf set-selection values.  Users will
-need to be familiar with the package debconf options.  Users can probe a
-packages' debconf settings by using ``debconf-get-selections``.
+- `extlinux <https://wiki.syslinux.org/wiki/index.php?title=EXTLINUX>`_
+  is really just a file format, similar to a grub configuration-file but much
+  less flexible. It specifies which OS options to present to the user.
 
-**selection_name**: *<debconf-set-selections input>*
+One or both can be installed.
 
-``debconf-set-selections`` is in the form::
+The following properties are used for both bootloaders:
 
-  <packagename> <packagename/option-name> <type> <value>
+**bootloaders**: *<list of bootloaders>*
 
-**Example**::
+Selects the bootloaders to use. Valid options are "grub" and "extlinux".
 
-  debconf_selections:
-    set1: |
-      cloud-init cloud-init/datasources multiselect MAAS
-      lxd lxd/bridge-name string lxdbr0
-    set2: lxd lxd/setup-bridge boolean true
+**replace_linux_default**: *<boolean: default True>*
 
+Controls whether grub-install will update the Linux Default target
+value during installation.
 
+**terminal**: *<['unmodified', 'console', ...]>*
 
-disable_overlayroot
-~~~~~~~~~~~~~~~~~~~
-Curtin disables overlayroot in the target by default.
+For grub, this configures the target-system grub-option GRUB_TERMINAL
+``terminal`` value which is written to
+/etc/default/grub.d/50-curtin-settings.cfg.  Curtin does not attempt to validate
+this string, grub2 has many values that it accepts and the list is platform
+dependent.
 
-**disable_overlayroot**: *<boolean: default True>*
+For extlinux, this puts the console string in an APPEND line for each OS.
 
-**Example**::
+If ``terminal`` is not provided, Curtin will set the value to 'console'.  If the
+``terminal`` value is 'unmodified' then Curtin will not set any value at all and
+will use Grub defaults.
 
-  disable_overlayroot: False
+extlinux
+""""""""
 
+Curtin can add an ``extlinux.conf`` file to a filesystem. This contains a list
+of possible kernels, etc. similar to grub. This is somewhat more flexible on
+ARM/RISC-V since it can use `FIT <https://fitspec.osfw.foundation/>`_ and deal
+with devicetree, verified boot, etc. automatically. It also avoids specifying
+which bootloader must be used, since extlinux is supported by U-Boot, for
+example.
 
 grub
-~~~~
-Curtin configures grub as the target machine's boot loader.  Users
+""""
+
+Curtin can configure grub as the target machine's grub boot loader.  Users
 can control a few options to tailor how the system will boot after
 installation.
 
@@ -194,11 +182,6 @@ installation.
 
 Specify a list of devices onto which grub will attempt to install.
 
-**replace_linux_default**: *<boolean: default True>*
-
-Controls whether grub-install will update the Linux Default target
-value during installation.
-
 **update_nvram**: *<boolean: default True>*
 
 Certain platforms, like ``uefi`` and ``prep`` systems utilize
@@ -217,16 +200,6 @@ When False, curtin writes "GRUB_DISABLE_OS_PROBER=true" to target system in
 /etc/default/grub.d/50-curtin-settings.cfg.  If True, curtin won't modify the
 grub configuration value in the target system.
 
-**terminal**: *<['unmodified', 'console', ...]>*
-
-Configure target system grub option GRUB_TERMINAL ``terminal`` value
-which is written to /etc/default/grub.d/50-curtin-settings.cfg.  Curtin
-does not attempt to validate this string, grub2 has many values that
-it accepts and the list is platform dependent.  If ``terminal`` is
-not provided, Curtin will set the value to 'console'.  If the ``terminal``
-value is 'unmodified' then Curtin will not set any value at all and will
-use Grub defaults.
-
 **reorder_uefi**: *<boolean: default True>*
 
 Curtin is typically used with MAAS where the systems are configured to boot
@@ -266,7 +239,9 @@ This setting is ignored if *update_nvram* is False.
 
 **Example**::
 
-  grub:
+  boot:
+     bootloaders:
+        - grub
      install_devices:
        - /dev/sda1
      replace_linux_default: False
@@ -276,38 +251,138 @@ This setting is ignored if *update_nvram* is False.
 
 **Default terminal value, GRUB_TERMINAL=console**::
 
-  grub:
+  boot:
+     bootloaders:
+        - grub
      install_devices:
        - /dev/sda1
 
 **Don't set GRUB_TERMINAL in target**::
 
-  grub:
+  boot:
+     bootloaders:
+        - grub
      install_devices:
        - /dev/sda1
      terminal: unmodified
 
 **Allow grub to probe for additional OSes**::
 
-  grub:
-    install_devices:
-      - /dev/sda1
+  boot:
+     bootloaders:
+        - grub
+     install_devices:
+        - /dev/sda1
      probe_additional_os: True
 
 **Avoid writting any settings to etc/default/grub.d/50-curtin-settings.cfg**::
 
-  grub:
-    install_devices:
-      - /dev/sda1
+  boot:
+     bootloaders:
+        - grub
+     install_devices:
+        - /dev/sda1
      probe_additional_os: True
      terminal: unmodified
 
 **Enable Fallback UEFI Reordering**::
 
-  grub:
+  boot:
+     bootloaders:
+        - grub
      reorder_uefi: true
      reorder_uefi_force_fallback: true
 
+extlinux
+""""""""
+
+There are no options specific to extlinux.
+
+**Example**::
+
+  boot:
+     bootloaders:
+        - grub
+        - extlinux
+     install_devices:
+        - /dev/sda1
+
+curthooks
+~~~~~~~~~
+Configure how Curtin determines what :ref:`curthooks` to run during the installation
+process.
+
+**mode**: *<['auto', 'builtin', 'target']>*
+
+The default mode is ``auto``.
+
+In ``auto`` mode, curtin will execute curthooks within the image if present.
+For images without curthooks inside, curtin will execute its built-in hooks.
+
+Currently the built-in curthooks support the following OS families:
+
+- Ubuntu
+- Centos
+
+When specifying ``builtin``, curtin will only run the curthooks present in
+Curtin ignoring any curthooks that may be present in the target operating
+system.
+
+When specifying ``target``, curtin will attempt run the curthooks in the target
+operating system.  If the target does NOT contain any curthooks, then the
+built-in curthooks will be run instead.
+
+Any errors during execution of curthooks (built-in or target) will fail the
+installation.
+
+**Example**::
+
+  # ignore any target curthooks
+  curthooks:
+    mode: builtin
+
+  # Only run target curthooks, fall back to built-in
+  curthooks:
+    mode: target
+
+
+debconf_selections
+~~~~~~~~~~~~~~~~~~
+Curtin will update the target with debconf set-selection values.  Users will
+need to be familiar with the package debconf options.  Users can probe a
+packages' debconf settings by using ``debconf-get-selections``.
+
+**selection_name**: *<debconf-set-selections input>*
+
+``debconf-set-selections`` is in the form::
+
+  <packagename> <packagename/option-name> <type> <value>
+
+**Example**::
+
+  debconf_selections:
+    set1: |
+      cloud-init cloud-init/datasources multiselect MAAS
+      lxd lxd/bridge-name string lxdbr0
+    set2: lxd lxd/setup-bridge boolean true
+
+
+
+disable_overlayroot
+~~~~~~~~~~~~~~~~~~~
+Curtin disables overlayroot in the target by default.
+
+**disable_overlayroot**: *<boolean: default True>*
+
+**Example**::
+
+  disable_overlayroot: False
+
+grub
+~~~~
+
+This is an alias for **boot** with *bootloader* set to "grub". It is provided
+to maintain backwards compatibility
 
 http_proxy
 ~~~~~~~~~~
diff --git a/doc/topics/storage.rst b/doc/topics/storage.rst
index f3d465f..5503d73 100644
--- a/doc/topics/storage.rst
+++ b/doc/topics/storage.rst
@@ -1170,6 +1170,7 @@ keystore system.  When **encryption_style** is not null, **keyfile** is
 required.
 
 This works as follows:
+
 * A LUKS device is created as a ZFS dataset in the ZPool.
 * The supplied passphrase (see **keyfile**) is used to encrypt the LUKS device.
 * The real key for the ZFS dataset is contained in the LUKS device as a simple
diff --git a/examples/tests/no-grub-file.yaml b/examples/tests/no-grub-file.yaml
index d5ba698..240dbb9 100644
--- a/examples/tests/no-grub-file.yaml
+++ b/examples/tests/no-grub-file.yaml
@@ -4,6 +4,7 @@ placeholder_simple_install: unused
 
 # configure curtin so it does not emit a grub config file
 # in etc/default/grub/grub.d
-grub:
+boot:
+   bootloaders: ['grub']
    probe_additional_os: true
    terminal: unmodified
diff --git a/tests/unittests/test_commands_install_extlinux.py b/tests/unittests/test_commands_install_extlinux.py
new file mode 100644
index 0000000..3e310eb
--- /dev/null
+++ b/tests/unittests/test_commands_install_extlinux.py
@@ -0,0 +1,133 @@
+# This file is part of curtin. See LICENSE file for copyright and license info.
+
+import os
+from pathlib import Path
+import tempfile
+
+from .helpers import CiTestCase
+
+from curtin import config
+from curtin import paths
+from curtin.commands import install_extlinux
+
+
+USE_EXTLINUX = ['extlinux']
+
+EXPECT_HDR = '''\
+## /boot/extlinux/extlinux.conf
+##
+## IMPORTANT WARNING
+##
+## The configuration of this file is generated automatically.
+## Do not edit this file manually, use: u-boot-update
+
+default l0
+menu title U-Boot menu
+prompt 0
+timeout 50
+'''
+
+EXPECT_BODY = '''
+
+label l0
+\tmenu label Ubuntu 22.04.5 LTS 6.8.0-48-generic
+\tlinux /vmlinuz-6.8.0-48-generic
+\tinitrd /initrd.img-6.8.0-48-generic
+\tappend root=/dev/mapper/vgubuntu-root ro quiet
+
+label l0r
+\tmenu label Ubuntu 22.04.5 LTS 6.8.0-48-generic (rescue target)
+\tlinux /vmlinuz-6.8.0-48-generic
+\tinitrd /initrd.img-6.8.0-48-generic
+\tappend root=/dev/mapper/vgubuntu-root ro single
+
+
+label l1
+\tmenu label Ubuntu 22.04.5 LTS 6.8.0-40-generic
+\tlinux /vmlinuz-6.8.0-40-generic
+\tinitrd /initrd.img-6.8.0-40-generic
+\tappend root=/dev/mapper/vgubuntu-root ro quiet
+
+label l1r
+\tmenu label Ubuntu 22.04.5 LTS 6.8.0-40-generic (rescue target)
+\tlinux /vmlinuz-6.8.0-40-generic
+\tinitrd /initrd.img-6.8.0-40-generic
+\tappend root=/dev/mapper/vgubuntu-root ro single
+
+
+label l2
+\tmenu label Ubuntu 22.04.5 LTS 5.15.0-127-generic
+\tlinux /vmlinuz-5.15.0-127-generic
+\tinitrd /initrd.img-5.15.0-127-generic
+\tappend root=/dev/mapper/vgubuntu-root ro quiet
+
+label l2r
+\tmenu label Ubuntu 22.04.5 LTS 5.15.0-127-generic (rescue target)
+\tlinux /vmlinuz-5.15.0-127-generic
+\tinitrd /initrd.img-5.15.0-127-generic
+\tappend root=/dev/mapper/vgubuntu-root ro single
+'''
+
+
+class TestInstallExtlinux(CiTestCase):
+    def setUp(self):
+        self.tmpdir = tempfile.TemporaryDirectory(suffix='-curtin')
+        self.target = self.tmpdir.name
+
+        versions = ['6.8.0-40', '5.15.0-127', '6.8.0-48']
+        boot = os.path.join(self.target, 'boot')
+        Path(f'{boot}').mkdir()
+        os.system(f'ls {boot}')
+        for ver in versions:
+            Path(f'{boot}/config-{ver}-generic').touch()
+            Path(f'{boot}/initrd.img-{ver}-generic').touch()
+            Path(f'{boot}/vmlinuz-{ver}-generic').touch()
+
+        Path(f'{self.target}/empty-dir').mkdir()
+        self.maxDiff = None
+
+    def test_get_kernel_list(self):
+        iter = paths.get_kernel_list(self.target, full_initrd_path=False)
+        self.assertEqual(
+            ('vmlinuz-6.8.0-48-generic', 'initrd.img-6.8.0-48-generic',
+             '6.8.0-48-generic'),
+            next(iter))
+        self.assertEqual(
+            ('vmlinuz-6.8.0-40-generic', 'initrd.img-6.8.0-40-generic',
+             '6.8.0-40-generic'),
+            next(iter))
+        self.assertEqual(
+            ('vmlinuz-5.15.0-127-generic', 'initrd.img-5.15.0-127-generic',
+             '5.15.0-127-generic'),
+            next(iter))
+        try:
+            val = next(iter)
+            raise ValueError(f'Extra value {val}')
+        except StopIteration:
+            pass
+
+    def test_empty(self):
+        out = install_extlinux.build_content(f'{self.target}/empty-dir',
+                                             config.BootCfg(USE_EXTLINUX))
+        self.assertEqual(out, EXPECT_HDR)
+
+    def test_normal(self):
+        out = install_extlinux.build_content(self.target,
+                                             config.BootCfg(USE_EXTLINUX))
+        self.assertEqual(EXPECT_HDR + EXPECT_BODY, out)
+
+    def test_no_recovery(self):
+        out = install_extlinux.build_content(self.target,
+                                             config.BootCfg(USE_EXTLINUX))
+        self.assertEqual(EXPECT_HDR + EXPECT_BODY, out)
+
+    def test_install(self):
+        install_extlinux.install_extlinux(self.target,
+                                          config.BootCfg(USE_EXTLINUX))
+        extlinux_path = self.target + '/boot/extlinux'
+        self.assertTrue(os.path.exists(extlinux_path))
+        extlinux_file = extlinux_path + '/extlinux.conf'
+        self.assertTrue(os.path.exists(extlinux_file))
+
+
+# vi: ts=4 expandtab syntax=python
diff --git a/tests/unittests/test_commands_install_grub.py b/tests/unittests/test_commands_install_grub.py
index 7b7b547..0adeb89 100644
--- a/tests/unittests/test_commands_install_grub.py
+++ b/tests/unittests/test_commands_install_grub.py
@@ -10,6 +10,8 @@ from .helpers import CiTestCase
 from unittest import mock
 import os
 
+USE_GRUB = ['grub']
+
 
 class TestGetGrubPackageName(CiTestCase):
 
@@ -204,7 +206,7 @@ class TestGetGrubPackageName(CiTestCase):
                                                osfamily=osfamily)
 
 
-class TestGetGrubConfigFile(CiTestCase):
+class TestGetBootCfgFile(CiTestCase):
 
     @mock.patch('curtin.commands.install_grub.distro.os_release')
     def test_grub_config_redhat(self, mock_os_release):
@@ -435,10 +437,10 @@ class TestReplaceGrubCmdlineLinuxDefault(CiTestCase):
         self.assertEqual(expected, found)
 
 
-class TestWriteGrubConfig(CiTestCase):
+class TestWriteBootCfg(CiTestCase):
 
     def setUp(self):
-        super(TestWriteGrubConfig, self).setUp()
+        super(TestWriteBootCfg, self).setUp()
         self.target = self.tmp_dir()
         self.grubdefault = "/etc/default/grub"
         self.grubconf = "/etc/default/grub.d/50-curtin.cfg"
@@ -457,7 +459,7 @@ class TestWriteGrubConfig(CiTestCase):
                 self.assertEqual(expected, found)
 
     def test_write_grub_config_defaults(self):
-        grubcfg = config.GrubConfig()
+        bootcfg = config.BootCfg(USE_GRUB)
         new_params = ['foo=bar', 'wark=1']
         expected_default = "\n".join([
              'GRUB_CMDLINE_LINUX_DEFAULT="foo=bar wark=1"', ''])
@@ -469,12 +471,12 @@ class TestWriteGrubConfig(CiTestCase):
              'GRUB_TERMINAL="console"'])
 
         install_grub.write_grub_config(
-            self.target, grubcfg, self.grubconf, new_params)
+            self.target, bootcfg, self.grubconf, new_params)
 
         self._verify_expected(expected_default, expected_curtin)
 
     def test_write_grub_config_no_replace(self):
-        grubcfg = config.GrubConfig(replace_linux_default=False)
+        bootcfg = config.BootCfg(USE_GRUB, replace_linux_default=False)
         new_params = ['foo=bar', 'wark=1']
         expected_default = "\n".join([])
         expected_curtin = "\n".join([
@@ -485,12 +487,12 @@ class TestWriteGrubConfig(CiTestCase):
              'GRUB_TERMINAL="console"'])
 
         install_grub.write_grub_config(
-            self.target, grubcfg, self.grubconf, new_params)
+            self.target, bootcfg, self.grubconf, new_params)
 
         self._verify_expected(expected_default, expected_curtin)
 
     def test_write_grub_config_disable_probe(self):
-        grubcfg = config.GrubConfig(probe_additional_os=False)
+        bootcfg = config.BootCfg(USE_GRUB, probe_additional_os=False)
         new_params = ['foo=bar', 'wark=1']
         expected_default = "\n".join([
              'GRUB_CMDLINE_LINUX_DEFAULT="foo=bar wark=1"', ''])
@@ -502,12 +504,12 @@ class TestWriteGrubConfig(CiTestCase):
              'GRUB_TERMINAL="console"'])
 
         install_grub.write_grub_config(
-            self.target, grubcfg, self.grubconf, new_params)
+            self.target, bootcfg, self.grubconf, new_params)
 
         self._verify_expected(expected_default, expected_curtin)
 
     def test_write_grub_config_enable_probe(self):
-        grubcfg = config.GrubConfig(probe_additional_os=True)
+        bootcfg = config.BootCfg(USE_GRUB, probe_additional_os=True)
         new_params = ['foo=bar', 'wark=1']
         expected_default = "\n".join([
              'GRUB_CMDLINE_LINUX_DEFAULT="foo=bar wark=1"', ''])
@@ -516,23 +518,23 @@ class TestWriteGrubConfig(CiTestCase):
              'GRUB_TERMINAL="console"'])
 
         install_grub.write_grub_config(
-            self.target, grubcfg, self.grubconf, new_params)
+            self.target, bootcfg, self.grubconf, new_params)
 
         self._verify_expected(expected_default, expected_curtin)
 
     def test_write_grub_config_no_grub_settings_file(self):
-        grubcfg = config.GrubConfig(
+        bootcfg = config.BootCfg(
+            USE_GRUB,
             probe_additional_os=True,
             terminal='unmodified')
         new_params = []
         install_grub.write_grub_config(
-            self.target, grubcfg, self.grubconf, new_params)
+            self.target, bootcfg, self.grubconf, new_params)
         self.assertTrue(os.path.exists(self.target_grubdefault))
         self.assertFalse(os.path.exists(self.target_grubconf))
 
     def test_write_grub_config_specify_terminal(self):
-        grubcfg = config.GrubConfig(
-            terminal='serial')
+        bootcfg = config.BootCfg(USE_GRUB, terminal='serial')
         new_params = ['foo=bar', 'wark=1']
         expected_default = "\n".join([
              'GRUB_CMDLINE_LINUX_DEFAULT="foo=bar wark=1"', ''])
@@ -544,12 +546,12 @@ class TestWriteGrubConfig(CiTestCase):
              'GRUB_TERMINAL="serial"'])
 
         install_grub.write_grub_config(
-            self.target, grubcfg, self.grubconf, new_params)
+            self.target, bootcfg, self.grubconf, new_params)
 
         self._verify_expected(expected_default, expected_curtin)
 
     def test_write_grub_config_terminal_unmodified(self):
-        grubcfg = config.GrubConfig(terminal='unmodified')
+        bootcfg = config.BootCfg(USE_GRUB, terminal='unmodified')
         new_params = ['foo=bar', 'wark=1']
         expected_default = "\n".join([
              'GRUB_CMDLINE_LINUX_DEFAULT="foo=bar wark=1"', ''])
@@ -559,7 +561,7 @@ class TestWriteGrubConfig(CiTestCase):
              'GRUB_DISABLE_OS_PROBER="true"', ''])
 
         install_grub.write_grub_config(
-            self.target, grubcfg, self.grubconf, new_params)
+            self.target, bootcfg, self.grubconf, new_params)
 
         self._verify_expected(expected_default, expected_curtin)
 
@@ -1638,13 +1640,14 @@ class TestInstallGrub(CiTestCase):
         devices = []
         with self.assertRaises(ValueError):
             install_grub.install_grub(
-                devices, self.target, uefi=False, grubcfg=config.GrubConfig())
+                devices, self.target, uefi=False,
+                bootcfg=config.BootCfg(USE_GRUB))
 
     def test_grub_install_raise_exception_on_no_target(self):
         devices = ['foobar']
         with self.assertRaises(ValueError):
             install_grub.install_grub(
-                devices, None, uefi=False, grubcfg=config.GrubConfig())
+                devices, None, uefi=False, bootcfg=config.BootCfg(USE_GRUB))
 
     def test_grub_install_raise_exception_on_s390x(self):
         self.m_distro_get_architecture.return_value = 's390x'
@@ -1652,7 +1655,8 @@ class TestInstallGrub(CiTestCase):
         devices = ['foobar']
         with self.assertRaises(RuntimeError):
             install_grub.install_grub(
-                devices, self.target, uefi=False, grubcfg=config.GrubConfig())
+                devices, self.target, uefi=False,
+                bootcfg=config.BootCfg(USE_GRUB))
 
     def test_grub_install_raise_exception_on_armv7(self):
         self.m_distro_get_architecture.return_value = 'armhf'
@@ -1660,7 +1664,8 @@ class TestInstallGrub(CiTestCase):
         devices = ['foobar']
         with self.assertRaises(RuntimeError):
             install_grub.install_grub(
-                devices, self.target, uefi=False, grubcfg=config.GrubConfig())
+                devices, self.target, uefi=False,
+                bootcfg=config.BootCfg(USE_GRUB))
 
     def test_grub_install_raise_exception_on_arm64_no_uefi(self):
         self.m_distro_get_architecture.return_value = 'arm64'
@@ -1668,12 +1673,13 @@ class TestInstallGrub(CiTestCase):
         devices = ['foobar']
         with self.assertRaises(RuntimeError):
             install_grub.install_grub(
-                devices, self.target, uefi=False, grubcfg=config.GrubConfig())
+                devices, self.target, uefi=False,
+                bootcfg=config.BootCfg(USE_GRUB))
 
     def test_grub_install_ubuntu(self):
         devices = ['/dev/disk-a-part1']
         uefi = False
-        grubcfg = config.GrubConfig()
+        bootcfg = config.BootCfg(USE_GRUB)
         grub_conf = self.tmp_path('grubconf')
         new_params = []
         self.m_get_grub_package_name.return_value = ('grub-pc', 'i386-pc')
@@ -1684,7 +1690,7 @@ class TestInstallGrub(CiTestCase):
             [['/bin/true']], [['/bin/false']])
 
         install_grub.install_grub(
-            devices, self.target, uefi=uefi, grubcfg=grubcfg)
+            devices, self.target, uefi=uefi, bootcfg=bootcfg)
 
         self.m_distro_get_distroinfo.assert_called_with(target=self.target)
         self.m_distro_get_architecture.assert_called_with(target=self.target)
@@ -1695,7 +1701,7 @@ class TestInstallGrub(CiTestCase):
                                                        self.distroinfo.family)
         self.m_get_carryover_params.assert_called_with(self.distroinfo)
         self.m_prepare_grub_dir.assert_called_with(self.target, grub_conf)
-        self.m_write_grub_config.assert_called_with(self.target, grubcfg,
+        self.m_write_grub_config.assert_called_with(self.target, bootcfg,
                                                     grub_conf, new_params)
         self.m_get_grub_install_command.assert_called_with(
             uefi, self.distroinfo, self.target)
@@ -1712,7 +1718,7 @@ class TestInstallGrub(CiTestCase):
     def test_uefi_grub_install_ubuntu(self):
         devices = ['/dev/disk-a-part1']
         uefi = True
-        grubcfg = config.GrubConfig(update_nvram=True)
+        bootcfg = config.BootCfg(USE_GRUB, update_nvram=True)
         grub_conf = self.tmp_path('grubconf')
         new_params = []
         grub_name = 'grub-efi-amd64'
@@ -1726,7 +1732,7 @@ class TestInstallGrub(CiTestCase):
             [['/bin/true']], [['/bin/false']])
 
         install_grub.install_grub(
-            devices, self.target, uefi=uefi, grubcfg=grubcfg)
+            devices, self.target, uefi=uefi, bootcfg=bootcfg)
 
         self.m_distro_get_distroinfo.assert_called_with(target=self.target)
         self.m_distro_get_architecture.assert_called_with(target=self.target)
@@ -1737,12 +1743,12 @@ class TestInstallGrub(CiTestCase):
                                                        self.distroinfo.family)
         self.m_get_carryover_params.assert_called_with(self.distroinfo)
         self.m_prepare_grub_dir.assert_called_with(self.target, grub_conf)
-        self.m_write_grub_config.assert_called_with(self.target, grubcfg,
+        self.m_write_grub_config.assert_called_with(self.target, bootcfg,
                                                     grub_conf, new_params)
         self.m_get_grub_install_command.assert_called_with(
             uefi, self.distroinfo, self.target)
         self.m_gen_uefi_install_commands.assert_called_with(
-            grub_name, grub_target, grub_cmd, grubcfg.update_nvram,
+            grub_name, grub_target, grub_cmd, bootcfg.update_nvram,
             self.distroinfo, devices, self.target)
 
         self.m_subp.assert_has_calls([
@@ -1755,7 +1761,7 @@ class TestInstallGrub(CiTestCase):
     def test_uefi_grub_install_ubuntu_multiple_esp(self):
         devices = ['/dev/disk-a-part1']
         uefi = True
-        grubcfg = config.GrubConfig(update_nvram=True)
+        bootcfg = config.BootCfg(USE_GRUB, update_nvram=True)
         grub_conf = self.tmp_path('grubconf')
         new_params = []
         grub_name = 'grub-efi-amd64'
@@ -1769,7 +1775,7 @@ class TestInstallGrub(CiTestCase):
             [['/bin/true']], [['/bin/false']])
 
         install_grub.install_grub(
-            devices, self.target, uefi=uefi, grubcfg=grubcfg)
+            devices, self.target, uefi=uefi, bootcfg=bootcfg)
 
         self.m_distro_get_distroinfo.assert_called_with(target=self.target)
         self.m_distro_get_architecture.assert_called_with(target=self.target)
@@ -1780,12 +1786,12 @@ class TestInstallGrub(CiTestCase):
                                                        self.distroinfo.family)
         self.m_get_carryover_params.assert_called_with(self.distroinfo)
         self.m_prepare_grub_dir.assert_called_with(self.target, grub_conf)
-        self.m_write_grub_config.assert_called_with(self.target, grubcfg,
+        self.m_write_grub_config.assert_called_with(self.target, bootcfg,
                                                     grub_conf, new_params)
         self.m_get_grub_install_command.assert_called_with(
             uefi, self.distroinfo, self.target)
         self.m_gen_uefi_install_commands.assert_called_with(
-            grub_name, grub_target, grub_cmd, grubcfg.update_nvram,
+            grub_name, grub_target, grub_cmd, bootcfg.update_nvram,
             self.distroinfo, devices, self.target)
 
         self.m_subp.assert_has_calls([
diff --git a/tests/unittests/test_config.py b/tests/unittests/test_config.py
index 1db3191..e25cdeb 100644
--- a/tests/unittests/test_config.py
+++ b/tests/unittests/test_config.py
@@ -226,4 +226,39 @@ class TestDeserializer(CiTestCase):
             deserializer.deserialize(UnionClass, {"val": None}))
 
 
+class TestBootCfg(CiTestCase):
+    def test_empty(self):
+        with self.assertRaises(TypeError) as exc:
+            config.BootCfg()
+        self.assertIn("missing 1 required positional argument: 'bootloaders'",
+                      str(exc.exception))
+
+    def test_not_list(self):
+        with self.assertRaises(ValueError) as exc:
+            config.BootCfg('invalid')
+        self.assertIn("bootloaders must be a list: invalid", str(exc.exception))
+
+    def test_empty_list(self):
+        with self.assertRaises(ValueError) as exc:
+            config.BootCfg([])
+        self.assertIn("Empty bootloaders list:", str(exc.exception))
+
+    def test_duplicate(self):
+        with self.assertRaises(ValueError) as exc:
+            config.BootCfg(['grub', 'grub'])
+        self.assertIn("bootloaders list contains duplicates: ['grub', 'grub']",
+                      str(exc.exception))
+
+    def test_invalid(self):
+        with self.assertRaises(ValueError) as exc:
+            config.BootCfg(['fred'])
+        self.assertIn("Unknown bootloader fred: ['fred']", str(exc.exception))
+
+    def test_valid(self):
+        config.BootCfg(['grub'])
+        config.BootCfg(['extlinux'])
+        config.BootCfg(['grub', 'extlinux'])
+        config.BootCfg(['extlinux', 'grub'])
+
+
 # vi: ts=4 expandtab syntax=python
diff --git a/tests/unittests/test_curthooks.py b/tests/unittests/test_curthooks.py
index e76eb54..e4a8483 100644
--- a/tests/unittests/test_curthooks.py
+++ b/tests/unittests/test_curthooks.py
@@ -447,7 +447,7 @@ class TestUpdateInitramfs(CiTestCase):
     def test_fails_if_no_tool_to_update_initramfs(self):
         with patch("curtin.commands.curthooks.glob.glob",
                    return_value=["/boot/vmlinuz"]):
-            with self.assertRaises(RuntimeError):
+            with self.assertRaises(ValueError):
                 curthooks.update_initramfs(self.target)
 
         with patch("curtin.commands.curthooks.glob.glob", return_value=[]):
@@ -489,10 +489,10 @@ class TestUpdateInitramfs(CiTestCase):
             call(['update-initramfs', '-c', '-k', kversion3],
                  target=self.target))
         subp_calls += self._subp_calls(
-            call(['update-initramfs', '-c', '-k', self.kversion],
+            call(['update-initramfs', '-c', '-k', kversion2],
                  target=self.target))
         subp_calls += self._subp_calls(
-            call(['update-initramfs', '-c', '-k', kversion2],
+            call(['update-initramfs', '-c', '-k', self.kversion],
                  target=self.target))
         self.mock_subp.assert_has_calls(subp_calls)
         self.assertEqual(24, self.mock_subp.call_count)
@@ -513,10 +513,10 @@ class TestUpdateInitramfs(CiTestCase):
         subp_calls = self._subp_calls(
             call(['dpkg-divert', '--list'], capture=True, target=self.target))
         subp_calls += self._subp_calls(
-            call(['update-initramfs', '-u', '-k', kversion2],
+            call(['update-initramfs', '-c', '-k', self.kversion],
                  target=self.target))
         subp_calls += self._subp_calls(
-            call(['update-initramfs', '-c', '-k', self.kversion],
+            call(['update-initramfs', '-u', '-k', kversion2],
                  target=self.target))
         self.mock_subp.assert_has_calls(subp_calls)
         self.assertEqual(18, self.mock_subp.call_count)
@@ -845,15 +845,18 @@ class TestSetupGrub(CiTestCase):
         cfg = {
             'grub_install_devices': ['/dev/vdb']
         }
-        curthooks.setup_grub(cfg, self.target, osfamily=self.distro_family,
-                             variant=self.variant)
+        curthooks.setup_boot(cfg, self.target, machine='amd64',
+                             stack_prefix='stack_prefix',
+                             osfamily=self.distro_family, variant=self.variant)
         self.m_install_grub.assert_called_with(
             ['/dev/vdb'], self.target, uefi=False,
-            grubcfg=config.GrubConfig(install_devices=['/dev/vdb']))
+            bootcfg=config.BootCfg(bootloaders=['grub'],
+                                   install_devices=['/dev/vdb']))
 
-    def test_uses_install_devices_in_grubcfg(self):
+    def test_uses_install_devices_in_bootcfg(self):
         cfg = {
-            'grub': {
+            'boot': {
+                'bootloaders': ['grub'],
                 'install_devices': ['/dev/vdb'],
             },
         }
@@ -862,13 +865,55 @@ class TestSetupGrub(CiTestCase):
             osfamily=self.distro_family, variant=self.variant)
         self.m_install_grub.assert_called_with(
             ['/dev/vdb'], self.target, uefi=False,
-            grubcfg=config.fromdict(config.GrubConfig, cfg.get('grub')))
+            bootcfg=config.fromdict(config.BootCfg, cfg.get('boot')))
+
+    def test_uses_old_schema_install_devices_in_grubcfg(self):
+        cfg = {
+            'grub': {
+                'install_devices': ['/dev/vdb'],
+            },
+        }
+        curthooks.setup_boot(
+            cfg, self.target, machine='amd64', stack_prefix='stack_prefix',
+            osfamily=self.distro_family, variant=self.variant)
+        self.m_install_grub.assert_called_with(
+            ['/dev/vdb'], self.target, uefi=False,
+            bootcfg=config.fromdict(config.BootCfg, cfg.get('boot')))
+
+    def test_calls_install_grub(self):
+        cfg = {
+            'boot': {
+                'bootloaders': ['grub'],
+                'install_devices': ['/dev/vdb'],
+            },
+        }
+        curthooks.setup_boot(
+            cfg, self.target, 'amd64', '/testing',
+            osfamily=self.distro_family, variant=self.variant)
+        self.m_install_grub.assert_called_with(
+            ['/dev/vdb'], self.target, uefi=False,
+            bootcfg=config.fromdict(config.BootCfg, cfg.get('boot')))
+
+    def test_skips_install_grub(self):
+        cfg = {
+            'boot': {
+                'bootloaders': ['grub'],
+                'install_devices': ['/dev/vdb'],
+            },
+        }
+        curthooks.setup_boot(
+            cfg, self.target, 'aarch64', '/testing',
+            osfamily=self.distro_family, variant=self.variant)
+        self.m_install_grub.assert_not_called()
 
     @patch('curtin.commands.block_meta.multipath')
     @patch('curtin.commands.curthooks.os.path.exists')
     def test_uses_grub_install_on_storage_config(self, m_exists, m_multipath):
         m_multipath.is_mpath_member.return_value = False
         cfg = {
+            'boot': {
+                'bootloaders': ['grub'],
+            },
             'storage': {
                 'version': 1,
                 'config': [
@@ -886,7 +931,8 @@ class TestSetupGrub(CiTestCase):
                              variant=self.variant)
         self.m_install_grub.assert_called_with(
             ['/dev/vdb'], self.target, uefi=False,
-            grubcfg=config.GrubConfig(install_devices=['/dev/vdb']))
+            bootcfg=config.BootCfg(bootloaders=['grub'],
+                                   install_devices=['/dev/vdb']))
 
     @patch('curtin.commands.block_meta.multipath')
     @patch('curtin.block.is_valid_device')
@@ -927,7 +973,8 @@ class TestSetupGrub(CiTestCase):
                     },
                 ]
             },
-            'grub': {
+            'boot': {
+                'bootloaders': ['grub'],
                 'update_nvram': False,
             },
         }
@@ -937,13 +984,15 @@ class TestSetupGrub(CiTestCase):
                              variant='centos')
         self.m_install_grub.assert_called_with(
             ['/dev/vdb1'], self.target, uefi=True,
-            grubcfg=config.GrubConfig(
+            bootcfg=config.BootCfg(
+                bootloaders=['grub'],
                 update_nvram=False,
                 install_devices=['/dev/vdb1']))
 
     def test_grub_install_installs_to_none_if_install_devices_None(self):
         cfg = {
-            'grub': {
+            'boot': {
+                'bootloaders': ['grub'],
                 'install_devices': None,
             },
         }
@@ -951,7 +1000,7 @@ class TestSetupGrub(CiTestCase):
                              variant=self.variant)
         self.m_install_grub.assert_called_with(
             ['none'], self.target, uefi=False,
-            grubcfg=config.GrubConfig(install_devices=None),
+            bootcfg=config.BootCfg(bootloaders=['grub'], install_devices=None),
         )
 
     @patch.object(util.ChrootableTarget, "__enter__", new=lambda a: a)
@@ -961,7 +1010,8 @@ class TestSetupGrub(CiTestCase):
         self.add_patch('curtin.util.get_efibootmgr', 'mock_efibootmgr')
         self.mock_is_uefi_bootable.return_value = True
         cfg = {
-            'grub': {
+            'boot': {
+                'bootloaders': ['grub'],
                 'install_devices': ['/dev/vdb'],
                 'update_nvram': True,
                 'remove_old_uefi_loaders': False,
@@ -982,7 +1032,7 @@ class TestSetupGrub(CiTestCase):
                              variant=self.variant)
         self.m_install_grub.assert_called_with(
             ['/dev/vdb'], self.target, uefi=True,
-            grubcfg=config.fromdict(config.GrubConfig, cfg.get('grub'))
+            bootcfg=config.fromdict(config.BootCfg, cfg.get('boot'))
         )
 
     @patch.object(util.ChrootableTarget, "__enter__", new=lambda a: a)
@@ -992,7 +1042,8 @@ class TestSetupGrub(CiTestCase):
         self.add_patch('curtin.util.get_efibootmgr', 'mock_efibootmgr')
         self.mock_is_uefi_bootable.return_value = True
         cfg = {
-            'grub': {
+            'boot': {
+                'bootloaders': ['grub'],
                 'install_devices': ['/dev/vdb'],
                 'update_nvram': True,
                 'remove_old_uefi_loaders': True,
@@ -1034,7 +1085,8 @@ class TestSetupGrub(CiTestCase):
         self.add_patch('curtin.util.get_efibootmgr', 'mock_efibootmgr')
         self.mock_is_uefi_bootable.return_value = True
         cfg = {
-            'grub': {
+            'boot': {
+                'bootloaders': ['grub'],
                 'install_devices': ['/dev/vdb'],
                 'update_nvram': True,
                 'remove_old_uefi_loaders': False,
@@ -1070,7 +1122,8 @@ class TestSetupGrub(CiTestCase):
         self.add_patch('curtin.util.get_efibootmgr', 'mock_efibootmgr')
         self.mock_is_uefi_bootable.return_value = True
         cfg = {
-            'grub': {
+            'boot': {
+                'bootloaders': ['grub'],
                 'install_devices': ['/dev/vdb'],
                 'update_nvram': True,
                 'remove_old_uefi_loaders': False,
@@ -1116,7 +1169,8 @@ class TestSetupGrub(CiTestCase):
                        'mock_remove_old_loaders')
         self.mock_is_uefi_bootable.return_value = True
         cfg = {
-            'grub': {
+            'boot': {
+                'bootloaders': ['grub'],
                 'install_devices': ['/dev/vdb'],
                 'update_nvram': True,
                 'remove_old_uefi_loaders': False,
@@ -1168,7 +1222,8 @@ class TestSetupGrub(CiTestCase):
         self.add_patch('curtin.util.get_efibootmgr', 'mock_efibootmgr')
         self.mock_is_uefi_bootable.return_value = True
         cfg = {
-            'grub': {
+            'boot': {
+                'bootloaders': ['grub'],
                 'install_devices': ['/dev/vdb'],
                 'update_nvram': True,
                 'remove_old_uefi_loaders': True,
@@ -1223,7 +1278,8 @@ class TestSetupGrub(CiTestCase):
         self.add_patch('curtin.util.get_efibootmgr', 'mock_efibootmgr')
         self.mock_is_uefi_bootable.return_value = True
         cfg = {
-            'grub': {
+            'boot': {
+                'bootloaders': ['grub'],
                 'install_devices': ['/dev/vdb'],
                 'update_nvram': True,
                 'remove_old_uefi_loaders': True,
@@ -1311,8 +1367,8 @@ class TestUefiRemoveDuplicateEntries(CiTestCase):
 
     @patch.object(util.ChrootableTarget, "__enter__", new=lambda a: a)
     def test_uefi_remove_duplicate_entries(self):
-        grubcfg = config.GrubConfig()
-        curthooks.uefi_remove_duplicate_entries(grubcfg, self.target)
+        bootcfg = config.BootCfg(['grub'])
+        curthooks.uefi_remove_duplicate_entries(bootcfg, self.target)
         self.assertEqual([
             call(['efibootmgr', '--bootnum=0001', '--delete-bootnum'],
                  target=self.target),
@@ -1322,11 +1378,11 @@ class TestUefiRemoveDuplicateEntries(CiTestCase):
 
     @patch.object(util.ChrootableTarget, "__enter__", new=lambda a: a)
     def test_uefi_remove_duplicate_entries_no_bootcurrent(self):
-        grubcfg = config.GrubConfig()
+        bootcfg = config.BootCfg(['grub'])
         efiout = copy_efi_state(self.efibootmgr_output)
         efiout.current = ''
         self.m_efibootmgr.return_value = efiout
-        curthooks.uefi_remove_duplicate_entries(grubcfg, self.target)
+        curthooks.uefi_remove_duplicate_entries(bootcfg, self.target)
         self.assertEqual([
             call(['efibootmgr', '--bootnum=0001', '--delete-bootnum'],
                  target=self.target),
@@ -1336,19 +1392,17 @@ class TestUefiRemoveDuplicateEntries(CiTestCase):
 
     @patch.object(util.ChrootableTarget, "__enter__", new=lambda a: a)
     def test_uefi_remove_duplicate_entries_disabled(self):
-        grubcfg = config.GrubConfig(
-            remove_duplicate_entries=False,
-            )
-        curthooks.uefi_remove_duplicate_entries(grubcfg, self.target)
+        bootcfg = config.BootCfg(['grub'], remove_duplicate_entries=False)
+        curthooks.uefi_remove_duplicate_entries(bootcfg, self.target)
         self.assertEqual([], self.m_subp.call_args_list)
 
     @patch.object(util.ChrootableTarget, "__enter__", new=lambda a: a)
     def test_uefi_remove_duplicate_entries_skip_bootcurrent(self):
-        grubcfg = config.GrubConfig()
+        bootcfg = config.BootCfg(['grub'])
         efiout = copy_efi_state(self.efibootmgr_output)
         efiout.current = '0003'
         self.m_efibootmgr.return_value = efiout
-        curthooks.uefi_remove_duplicate_entries(grubcfg, self.target)
+        curthooks.uefi_remove_duplicate_entries(bootcfg, self.target)
         self.assertEqual([
             call(['efibootmgr', '--bootnum=0000', '--delete-bootnum'],
                  target=self.target),
@@ -1358,7 +1412,7 @@ class TestUefiRemoveDuplicateEntries(CiTestCase):
 
     @patch.object(util.ChrootableTarget, "__enter__", new=lambda a: a)
     def test_uefi_remove_duplicate_entries_no_change(self):
-        grubcfg = config.GrubConfig()
+        bootcfg = config.BootCfg(['grub'])
         self.m_efibootmgr.return_value = util.EFIBootState(
             order=[],
             timeout='',
@@ -1377,7 +1431,7 @@ class TestUefiRemoveDuplicateEntries(CiTestCase):
                     path='HD(1,GPT)/File(\\EFI\\sles\\shimx64.efi)',
                 ),
             })
-        curthooks.uefi_remove_duplicate_entries(grubcfg, self.target)
+        curthooks.uefi_remove_duplicate_entries(bootcfg, self.target)
         self.assertEqual([], self.m_subp.call_args_list)
 
 

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