Automatic syslinux.cfg generator for petitboot

gensyslinux.py

#!/usr/bin/env python3

import os
import re
import sys

BOOT_DIR = "/boot/"
ENTRY_NAME_PREFIX = "Gentoo Linux"
APPEND = "crypt_root=UUID=76543706-8215-4e11-bbfb-8acf447d6bb7 root=/dev/mapper/root"
KERNEL_RE = "vmlinux.*[0-9]+\.[0-9]+\.[0-9]+.*"
INITRD_RE = "initramfs.*[0-9]+\.[0-9]+\.[0-9]+.*"

def file_modified_key(elem):
    return os.path.getmtime(BOOT_DIR + elem)

def get_version_from_filename(filename):
    # Assumes file ends with version.
    # Ex. "vmlinux-4.18.10-gentoo" returns "4.18.10-gentoo"
    return re.findall(".*([0-9]+\.[0-9]+\.[0-9]+.*)", filename)[0]

def generate_entry_name(version):
    return ENTRY_NAME_PREFIX + " " + version

def generate_entry(kernel, initrd):
    version = get_version_from_filename(kernel)
    output = "LABEL " + generate_entry_name(version) + "\n"
    output += "\tKERNEL /" +  kernel + "\n"
    if initrd is not None:
        output += "\tINITRD /" + initrd + "\n"
    output += "\tAPPEND " + APPEND + "\n"
    return output

def main():
    kernels = [f for f in os.listdir(BOOT_DIR) if re.match(KERNEL_RE, f)]
    initrds = [f for f in os.listdir(BOOT_DIR) if re.match(INITRD_RE, f)]

    # Sort by date modified
    kernels.sort(key=file_modified_key, reverse=True)
    initrds.sort(key=file_modified_key, reverse=True)

    if len(kernels) == 0:
        sys.stderr.write("No kernels found! Check BOOT_DIR and KERNEL_RE!\n")
        sys.exit(1)

    # Generate syslinux. Use the newest kernel as default.
    sysconfig_out = "DEFAULT " + generate_entry_name(get_version_from_filename(kernels[0])) + "\n"
    for i in range(len(kernels)):
        version = get_version_from_filename(kernels[i])
        # Get the matching initrd if it was found
        try:
            initrd = [x for x in initrds if get_version_from_filename(x) == version][0]
        except:
            initrd = None

        # Generate entry and append to output
        sysconfig_out += generate_entry(kernels[i], initrd) + "\n"

    # Print output
    sys.stdout.write(sysconfig_out)

if __name__ == "__main__":
    main()