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nixos/systemd-boot: fix systemd-boot-builder dowgrade to fail

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Since, 4ddc78818e systemd-boot-builder
is broken in two ways:

  * if no systemd-boot is currently installed *and* the NIXOS_INSTALL_BOOTLOADER
    env variable is not set, it will try to run "bootctl update", which will fail
  * if the currently installed systemd-boot version is newer than the version
    we're about to install, it will also try to run "bootctl update", which will fail

This patch changes the behaviour,

  * for the first case to still fail, but not even bother to try running
    "bootctl update" and instead erroring out with an exception
  * for the second case to leave the newer version in place, restoring
    the pre - 4ddc78818e behaviour

To do the proper version check a new "should_update" helper function was introduced,
mimicing the compare_product C function from bootctl. If the following systemd
issue gets resolved, we would have a nice way to get rid of this function:

> https://github.com/systemd/systemd/issues/23450

This change allows to again switch to a different NixOS configuration which contains
an older systemd-boot.

Co-authored-by: Martin Weinelt <mweinelt@users.noreply.github.com>
This commit is contained in:
Matthias Treydte 2022-05-13 12:09:25 +02:00
parent 2e01fc66bc
commit a30de3b849
1 changed files with 31 additions and 15 deletions
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46
nixos/modules/system/boot/loader/systemd-boot/systemd-boot-builder.py
View file

@ -204,6 +204,20 @@ def get_profiles() -> List[str]:
else:
return []
def should_update(v_from: str, v_to: str) -> bool:
# see https://github.com/systemd/systemd/blob/main/src/boot/bootctl.c compare_product function
len_from = len(v_from)
len_to = len(v_to)
if len_from < len_to:
return False
if len_from > len_to:
return True
return v_from < v_to
def main() -> None:
parser = argparse.ArgumentParser(description='Update NixOS-related systemd-boot files')
@ -244,27 +258,29 @@ def main() -> None:
subprocess.check_call(["@systemd@/bin/bootctl", "--path=@efiSysMountPoint@"] + flags + ["install"])
else:
# Update bootloader to latest if needed
systemd_version = subprocess.check_output(["@systemd@/bin/bootctl", "--version"], universal_newlines=True).split()[2]
sdboot_status = subprocess.check_output(["@systemd@/bin/bootctl", "--path=@efiSysMountPoint@", "status"], universal_newlines=True)
available_out = subprocess.check_output(["@systemd@/bin/bootctl", "--version"], universal_newlines=True).split()[2]
installed_out = subprocess.check_output(["@systemd@/bin/bootctl", "--path=@efiSysMountPoint@", "status"], universal_newlines=True)
# See status_binaries() in systemd bootctl.c for code which generates this
m = re.search("^\W+File:.*/EFI/(BOOT|systemd)/.*\.efi \(systemd-boot ([\d.]+[^)]*)\)$",
sdboot_status, re.IGNORECASE | re.MULTILINE)
installed_match = re.search(r"^\W+File:.*/EFI/(?:BOOT|systemd)/.*\.efi \(systemd-boot ([\d.]+[^)]*)\)$",
installed_out, re.IGNORECASE | re.MULTILINE)
needs_install = False
available_match = re.search(r"^\((.*)\)$", available_out)
if m is None:
print("could not find any previously installed systemd-boot, installing.")
# Let systemd-boot attempt an installation if a previous one wasn't found
needs_install = True
else:
sdboot_version = f'({m.group(2)})'
if systemd_version != sdboot_version:
print("updating systemd-boot from %s to %s" % (sdboot_version, systemd_version))
needs_install = True
if installed_match is None:
raise Exception("could not find any previously installed systemd-boot")
if needs_install:
if available_match is None:
raise Exception("could not determine systemd-boot version")
installed_version = installed_match.group(1)
available_version = available_match.group(1)
if should_update(installed_version, available_version):
print("updating systemd-boot from %s to %s" % (installed_version, available_version))
subprocess.check_call(["@systemd@/bin/bootctl", "--path=@efiSysMountPoint@", "update"])
else:
print("leaving systemd-boot %s in place (%s is not newer)" % (installed_version, available_version))
mkdir_p("@efiSysMountPoint@/efi/nixos")
mkdir_p("@efiSysMountPoint@/loader/entries")