135 lines
3.7 KiB
Python
135 lines
3.7 KiB
Python
#!/bin/env python3
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"""Update EFI boot entries for Linux kernels configured with EFISTUB.
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Requires root access.
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USAGE: efi-update PATH
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PATH points to a JSON file which holds the boot entries to insert. This file is
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an array of objects where each object is one boot entry and the order of each
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entry determines its order in the boot sequence.
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Each entry follows this schema:
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- label: the name of this entry (as it should appear in the boot menu)
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- device: the path to the device holding the kernel to boot
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- partition: the partition on the device (above) holding the kernel
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- kernel: the name of the kernel to boot (something like "linux-lts")
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- root: and object like:
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- path: the device path of the root partition
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- fstype: the filesytem type of the root partition
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- mountopts: an array of mount options for the root file system
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- params: an array of kernel parameters to pass (in addition to those for root)
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ASSUMPTIONS:
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- linux EFISTUB kernels only
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- no secondary bootloader (eg grub)
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- root filesystem mounts as rw
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- initramfs exists (eg no monolithic kernels)
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- initramfs and loader paths are named according to the kernel
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"""
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import sys
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import json
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import re
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import subprocess as sp
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from shutil import which
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from itertools import chain
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EFIEXE = "efibootmgr"
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def call_efibootmgr(args):
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"""Call efibootmgr (quietly) with ARGS"""
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return sp.run([EFIEXE, "-q", *args], check=True)
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def read_entries():
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"""Read boot entries from JSON file"""
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if len(sys.argv) != 2:
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print("must supply entry JSON as single argument")
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sys.exit(1)
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with open(sys.argv[1], encoding="utf-8") as file:
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# hack to remove comments from (nonstandard) json
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out = re.sub("//.*?\n", "", file.read())
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return json.loads(re.sub("/\\*.*?\\*/", "", out))
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def delete_entry(bootnum):
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"""Remove the entry associated with BOOTNUM"""
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call_efibootmgr(["-b", str(bootnum), "-B"])
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def insert_entry(bootnum, entry):
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"""Insert ENTRY at position BOOTNUM"""
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def fmt_keyval(key, val):
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return f"{key}={val}"
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def fmt_flag_(flag, arg, quote=False):
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return [f"-{flag}", f"'{arg}'" if quote else f"{arg}"]
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def fmt_flag(flag, key, quote=False):
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return fmt_flag_(flag, entry[key], quote)
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kernel = entry["kernel"]
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root = entry["root"]
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unicode_args = " ".join(
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[
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fmt_keyval("root", root["path"]),
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"rw",
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fmt_keyval("rootfstype", root["fstype"]),
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fmt_keyval("rootflags", ",".join(root["mountopts"])),
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*entry["params"],
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fmt_keyval("initrd", f"/initramfs-{kernel}.img"),
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]
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)
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args = [
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fmt_flag_("b", bootnum),
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["-c"],
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fmt_flag("L", "label"),
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fmt_flag("d", "device"),
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fmt_flag("p", "partition"),
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fmt_flag_("l", f"/vmlinuz-{kernel}"),
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fmt_flag_("u", unicode_args),
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]
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call_efibootmgr([*chain(*args)])
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def update_entry(bootnum, entry):
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"""Update (delete and insert) ENTRY at position BOOTNUM"""
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print(f"Updating entry '{entry['label']}'")
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try:
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delete_entry(bootnum)
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except sp.CalledProcessError:
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pass
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insert_entry(bootnum, entry)
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def remove_dups():
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"""Remove duplicate boot entries if they exist"""
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call_efibootmgr("-D")
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def set_order(entries):
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"""Set the boot order according to the order of ENTRIES"""
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call_efibootmgr("-O")
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order = ",".join([str(i) for i in range(0, len(entries))])
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call_efibootmgr(order)
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def main():
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"""Update all EFI entries"""
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if not which(EFIEXE):
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print(f"{EFIEXE} not found")
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sys.exit(1)
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entries = read_entries()
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for bootnum, entry in enumerate(entries):
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update_entry(bootnum, entry)
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remove_dups()
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set_order(entries)
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main()
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