set_default_grub_version.py

import os
import re
import subprocess


class GrubConf:
    """Handles operations related to the GRUB configuration file."""

    def __init__(self, path):
        """Initialize with the path to the GRUB configuration file."""
        if not os.path.exists(path):
            raise FileNotFoundError(f"GRUB configuration file does not exist at {path}")
        self.path = path

    def get_kernel_versions(self):
        """Extract kernel versions from the configuration file."""
        pattern = re.compile(r"kernel\s+/boot/vmlinuz-([\d.]+)")
        with open(self.path) as file:
            return [match.group(1) for match in pattern.finditer(file.read()) if match.group(1)]

    def set_default_kernel(self, version):
        """Set the specified kernel version as default in the configuration file."""
        sed_command = ["/usr/bin/sed", "-i.bak", f"s/default=.*/default={version}/", self.path]
        try:
            subprocess.run(sed_command, check=True)
        except subprocess.CalledProcessError as e:
            raise RuntimeError("Failed to update the GRUB configuration") from e


class KernelManager:
    """Manages kernel versions for the application."""

    def __init__(self, grub_conf):
        """Initialize with a GrubConf instance."""
        self.grub_conf = grub_conf

    def set_highest_kernel_as_default(self):
        """Set the highest kernel version as the default one."""
        versions = self.grub_conf.get_kernel_versions()
        if not versions:
            print("No kernel versions found in GRUB configuration.")
            return

        highest_version = max(versions)
        self.grub_conf.set_default_kernel(highest_version)
        print(f"Successfully set default kernel to {highest_version}.")


def main():
    GRUB_PATH = "/etc/grub.conf"
    try:
        grub_conf = GrubConf(GRUB_PATH)
        kernel_manager = KernelManager(grub_conf)
        kernel_manager.set_highest_kernel_as_default()
    except FileNotFoundError as e:
        print(e)
    except RuntimeError as e:
        print(e)


if __name__ == "__main__":
    main()