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Use grubby to update kernel command line arguments #511

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bf914ac
Add `remove_from_option` method to `Grub2ConfigEditor`
mihaelabalutoiu Sep 8, 2026
6e83c6c
Handle kernel command line arguments in the base OSMorphing tools
mihaelabalutoiu Sep 8, 2026
f6177de
Use `grubby` to update kernel command line arguments on Red Hat
mihaelabalutoiu Sep 8, 2026
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71 changes: 48 additions & 23 deletions coriolis/osmorphing/base.py
View file
Open in desktop
Original file line number Diff line number Diff line change
Expand Up @@ -17,6 +17,7 @@
from coriolis.osmorphing.netpreserver import factory

GRUB2_SERIAL = "serial --word=8 --stop=1 --speed=%d --parity=%s --unit=0"
GRUB2_CMDLINE_OPTIONS = ["GRUB_CMDLINE_LINUX", "GRUB_CMDLINE_LINUX_DEFAULT"]
LOG = logging.getLogger(__name__)

IFCFG_TEMPLATE = """
Expand Down Expand Up @@ -756,10 +757,7 @@ def _ensure_cloud_init_not_disabled(self):
if self._test_path(grub_conf_disabler):
contents = self._read_file_sudo(grub_conf_disabler)
if "cloud-init=disabled" in contents:
self._exec_cmd_chroot(
"sed -i '/cloud-init=disabled/d' %s" % grub_conf_disabler
)
self._schedule_grub2_update()
self._update_kernel_cmdline_args(args_to_remove=["cloud-init=disabled"])

@Dany9966 Dany9966 Aug 31, 2026 •
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I don't like that both grub update and grubby are being called. It should be the one or the other, not both.

An ideal implementation would be to call for _update_kernel_cmdline_args indeed, but you only implemented it for redhat based. There should also be a debian implementation which does the former (reads /etc/default/grub, removes/adds/edits the cmdline, schedules grub2 update).

I propose the following:

  1. Use Grub2ConfigEditor whenever possible instead of sed-ing the file directly.
    This implies implementing a new method to remove cmdline entries, call it remove_from_option
    This method should pretty much emulate what grubby does on redhat, and that is if you pass a single option
    (--remove-args=cloud-init), then it will be removed even if it's a key_val, no matter what value cloud-init has
    in cmdline. If you pass a key_val, then only remove the key if the value matches
    (--remove-args=cloud-init=disabled only remove cloud-init from cmdline if it's disabled, but won't
    remove cloud-init=enabled).

  2. We should somehow abstractize this for redhat. On base, when calling for _update_kernel_cmdline_args,
    it should instantiate a Grub2ConfigEditor, append or remove from GRUB_CMDLINE_LINUX and
    GRUB_CMDLINE_LINUX_DEFAULT options (depending on what args_to_add or args_to_remove are being
    passed).
    If it's redhat, then simply use grubby to handle args_to_add/args_to_remove

  3. (only if grubby commands take too long, otherwise treat this as optional) I think the final grubby command should also be run once at the end, so add some schedule_grubby
    methods as well when adding args to remove/add. (similar to _schedule_grub2_update)


def _reset_cloud_init_run(self):
self._exec_cmd_chroot("cloud-init clean --logs")
Expand Down Expand Up @@ -930,26 +928,53 @@ def replace_in_cfg(opt, val):
cfg = self._read_file_sudo(config_obj["location"])
LOG.warning("TEMP CONFIG IS: %r" % cfg)

def _set_grub2_cmdline(self, config_obj, options, clobber=False):
kernel_cmd_def = config_obj["contents"].get("GRUB_CMDLINE_LINUX_DEFAULT")
kernel_cmd = config_obj["contents"].get("GRUB_CMDLINE_LINUX")
replace = kernel_cmd is not None
@staticmethod
def _normalize_kernel_cmdline_args(args):
"""Returns the given kernel command line arguments as a list."""

if clobber:
opt = " ".join(options)
self.set_grub_value("GRUB_CMDLINE_LINUX", opt, config_obj, replace=replace)
return
kernel_cmd_def = kernel_cmd_def or ""
kernel_cmd = kernel_cmd or ""
to_add = []
for option in options:
if option not in kernel_cmd_def and option not in kernel_cmd:
to_add.append(option)
if len(to_add):
kernel_cmd = "%s %s" % (kernel_cmd, " ".join(to_add))
self.set_grub_value(
"GRUB_CMDLINE_LINUX", kernel_cmd, config_obj, replace=replace
if isinstance(args, str):
return [args] if args else []
return list(args or [])

@staticmethod
def _get_kernel_cmdline_arg_value(arg):
"""Converts a kernel command line argument to a Grub2ConfigEditor value."""

key, separator, value = arg.partition("=")
if not separator:
return {"opt_type": "single", "opt_val": key}
return {"opt_type": "key_val", "opt_key": key, "opt_val": value}

def _update_kernel_cmdline_args(self, args_to_add=None, args_to_remove=None):
"""Updates the kernel command line arguments in the GRUB2 defaults.

The arguments are edited in '/etc/default/grub' and the GRUB2 config
regeneration is scheduled so that they reach the boot entries.
"""
args_to_add = self._normalize_kernel_cmdline_args(args_to_add)
args_to_remove = self._normalize_kernel_cmdline_args(args_to_remove)
if not args_to_add and not args_to_remove:
return False

grub_conf = self._get_grub_default_conf()
if not grub_conf:
LOG.warning(
"Could not find '/etc/default/grub'. Skipping kernel command "
"line arguments update."
)
return False

cfg = utils.Grub2ConfigEditor(self._read_file_sudo(grub_conf))
for option in GRUB2_CMDLINE_OPTIONS:
for arg in args_to_remove:
cfg.remove_from_option(option, self._get_kernel_cmdline_arg_value(arg))
for arg in args_to_add:
cfg.remove_from_option(option, self._get_kernel_cmdline_arg_value(arg))
cfg.append_to_option(option, {"opt_type": "single", "opt_val": arg})
self._write_file_sudo(grub_conf.lstrip("/"), cfg.dump())
self._schedule_grub2_update()

return True

def _get_grub_default_conf(self):
grub_conf = "/etc/default/grub"
Expand Down Expand Up @@ -1055,8 +1080,8 @@ def _set_grub2_console_settings(
c = "console=%s" % console
options.append(c)

self._set_grub2_cmdline(config_obj, options)
self._apply_grub2_config(config_obj, execute_update_grub)
self._update_kernel_cmdline_args(args_to_add=options)

def _add_net_udev_rules(self, net_ifaces_info):
coriolis_udev_rules_file = "etc/udev/rules.d/99-coriolis-net.rules"
Expand Down
26 changes: 2 additions & 24 deletions coriolis/osmorphing/debian.py
View file
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Original file line number Diff line number Diff line change
Expand Up @@ -8,7 +8,7 @@
import yaml
from oslo_log import log as logging

from coriolis import constants, exception, utils
from coriolis import constants, exception
from coriolis.osmorphing import base
from coriolis.osmorphing.osdetect import debian as debian_osdetect

Expand Down Expand Up @@ -69,29 +69,7 @@ def check_os_supported(cls, detected_os_info):
)

def disable_predictable_nic_names(self):
grub_cfg = "etc/default/grub"
if self._test_path_chroot(grub_cfg) is False:
return
contents = self._read_file_sudo(grub_cfg)
cfg = utils.Grub2ConfigEditor(contents)
cfg.append_to_option(
"GRUB_CMDLINE_LINUX_DEFAULT",
{"opt_type": "key_val", "opt_key": "net.ifnames", "opt_val": 0},
)
cfg.append_to_option(
"GRUB_CMDLINE_LINUX_DEFAULT",
{"opt_type": "key_val", "opt_key": "biosdevname", "opt_val": 0},
)
cfg.append_to_option(
"GRUB_CMDLINE_LINUX",
{"opt_type": "key_val", "opt_key": "net.ifnames", "opt_val": 0},
)
cfg.append_to_option(
"GRUB_CMDLINE_LINUX",
{"opt_type": "key_val", "opt_key": "biosdevname", "opt_val": 0},
)
self._write_file_sudo("etc/default/grub", cfg.dump())
self._schedule_grub2_update()
self._update_kernel_cmdline_args(args_to_add=["net.ifnames=0", "biosdevname=0"])

def get_update_grub2_command(self):
return "update-grub"
Expand Down
33 changes: 31 additions & 2 deletions coriolis/osmorphing/redhat.py
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Original file line number Diff line number Diff line change
Expand Up @@ -3,6 +3,7 @@

import os
import re
import shlex
import uuid

from oslo_log import log as logging
Expand Down Expand Up @@ -56,8 +57,36 @@ def __init__(
)

def disable_predictable_nic_names(self):
cmd = 'grubby --update-kernel=ALL --args="%s"'
self._exec_cmd_chroot(cmd % "net.ifnames=0 biosdevname=0")
self._update_kernel_cmdline_args(args_to_add=["net.ifnames=0", "biosdevname=0"])

def _update_kernel_cmdline_args(self, args_to_add=None, args_to_remove=None):
"""Updates the kernel command line arguments using 'grubby'.

On BLS-based releases (RHEL 9+), 'grub2-mkconfig' does not propagate
kernel arguments into the '/boot/loader/entries' boot entries.
'grubby --update-kernel=ALL' updates every boot entry and replaces
the base implementation rather than supplementing it, so it must not
be paired with a GRUB2 regeneration for the same update.

"""

args_to_add = self._normalize_kernel_cmdline_args(args_to_add)
args_to_remove = self._normalize_kernel_cmdline_args(args_to_remove)
if not args_to_add and not args_to_remove:
return False

for option, args in (
("--remove-args", args_to_remove),
("--args", args_to_add),
):
if not args:
continue
self._exec_cmd_chroot(
"grubby --update-kernel=ALL %s=%s"
% (option, shlex.quote(" ".join(args)))
)

return True

def get_update_grub2_command(self):
location = self._get_grub2_cfg_location()
Expand Down
28 changes: 1 addition & 27 deletions coriolis/osmorphing/suse.py
View file
Open in desktop
Original file line number Diff line number Diff line change
Expand Up @@ -69,33 +69,7 @@ def check_os_supported(cls, detected_os_info):
return False

def disable_predictable_nic_names(self):
grub_cfg = "etc/default/grub"
if not self._test_path(grub_cfg):
LOG.warning(
"Could not find /%s. Skipping predictable NIC names disabling.",
grub_cfg,
)
return
contents = self._read_file_sudo(grub_cfg)
cfg = utils.Grub2ConfigEditor(contents)
cfg.append_to_option(
"GRUB_CMDLINE_LINUX_DEFAULT",
{"opt_type": "key_val", "opt_key": "net.ifnames", "opt_val": 0},
)
cfg.append_to_option(
"GRUB_CMDLINE_LINUX_DEFAULT",
{"opt_type": "key_val", "opt_key": "biosdevname", "opt_val": 0},
)
cfg.append_to_option(
"GRUB_CMDLINE_LINUX",
{"opt_type": "key_val", "opt_key": "net.ifnames", "opt_val": 0},
)
cfg.append_to_option(
"GRUB_CMDLINE_LINUX",
{"opt_type": "key_val", "opt_key": "biosdevname", "opt_val": 0},
)
self._write_file_sudo("etc/default/grub", cfg.dump())
self._schedule_grub2_update()
self._update_kernel_cmdline_args(args_to_add=["net.ifnames=0", "biosdevname=0"])

def set_net_config(self, nics_info, dhcp):
if dhcp:
Expand Down
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