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@@ -0,0 +1,87 @@
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+#!/usr/bin/env python3
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+
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+from __future__ import annotations
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+
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+import subprocess
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+import sys
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+from pathlib import Path
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+from typing import Any
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+
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+
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+def grub2_editenv(*args: Any, **kwargs: Any) -> str:
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+ subprocess.run(["grub2-editenv", *args], check=True, **kwargs)
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+
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+
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+def main() -> int:
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+ boot: Path = Path("/boot")
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+ mid: Path = Path("/etc/machine-id")
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+
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+ if not boot.exists():
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+ print("ERROR: /boot directory does not exist")
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+ return 1
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+
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+ if not mid.exists():
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+ print("ERROR: /etc/machine-id does not exist")
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+ return 1
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+
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+ blsdir: Path = boot / "loader" / "entries"
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+
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+ if not blsdir.exists():
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+ print("ERROR: /boot/loader/entries does not exist")
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+ return 1
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+
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+ try:
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+ grub2_editenv("--help", capture_output=True)
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+ except:
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+ print("ERROR: grub2-editenv is not working")
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+ return 1
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+
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+ # Get list of surface kernels sorted by timestamp.
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+ #
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+ # We use creation time here because it represents when the kernel was installed.
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+ # Modification time can be a bit wonky and seems to correspond to the build date.
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+ kernels: list[Path] = sorted(
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+ boot.glob("vmlinuz-*.surface.*"),
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+ key=lambda x: x.stat().st_ctime,
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+ reverse=True,
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+ )
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+
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+ if len(kernels) == 0:
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+ print("ERROR: Failed to find a surface kernel")
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+ return 1
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+
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+ # The saved_entry property from grubenv determines what kernel is booted by default.
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+ # Its value is the filename of the BLS entry in /boot/loader/entries minus the file extension.
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+ #
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+ # The BLS files are named using a combination of the machine ID and the version string
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+ # of the kernel that is being booted. Since we have the vmlinux, we can get the version
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+ # from its name, and the machine ID from /etc/machine-id.
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+ #
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+ # This allows setting the default kernel without calling grubby or having to figure out
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+ # which path GRUB will use to boot the kernel.
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+
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+ kernel: Path = kernels[0]
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+
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+ machineid: str = mid.read_text().strip()
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+ version: str = kernel.name.lstrip("vmlinuz-")
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+
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+ blscfg: Path = blsdir / "{}-{}.conf".format(machineid, version)
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+
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+ # Make sure the config really exists
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+ if not blscfg.exists():
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+ print("ERROR: {} does not exist".format(blscfg))
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+ return 1
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+
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+ print("Kernel: {}".format(kernel))
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+ print("BLS entry: {}".format(blscfg))
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+
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+ grub2_editenv("-", "set", "saved_entry={}".format(blscfg.stem))
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+
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+ # Update timestamp for rEFInd and ensure it is marked as latest across all kernels
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+ kernel.touch(exist_ok=True)
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+
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+ return 0
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+
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+
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+if __name__ == "__main__":
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+ sys.exit(main())
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Dorian Stoll