Remove old Debian/Ubuntu kernel versions.

remove_old_kernels

#!/usr/bin/env python3
# -*- coding: utf-8 -*-
# vim: set ts=4 sw=4 sts=4 et:

from distutils.version import LooseVersion
from subprocess import Popen, PIPE
from re import compile as rcomp
from os import uname, system
from sys import exit
from argparse import ArgumentParser, ArgumentTypeError
from functools import cmp_to_key


def cmp_version(a, b):
    return LooseVersion(a) < LooseVersion(b)


def dpkg_get_selections():
    proc = Popen(('dpkg', '--get-selections'), stdout=PIPE, close_fds=True)
    for i in proc.stdout:
        yield i.decode('utf-8')

    proc.wait()


def kernel_versions():
    linux_image_re = rcomp(r'^linux-image-([\d.-]+-\S+).*')
    for i in dpkg_get_selections():
        m = linux_image_re.match(i)
        if m:
            yield m.group(1)


def packages(versions):
    for i in dpkg_get_selections():
        for j in versions:
            if j in i:
                yield i.split()[0]
                break


def keep_type(x):
    x = int(x)
    if x < 1:
        raise ArgumentTypeError("Minimum keep is 1")

    return x


def parse_args():
    parser = ArgumentParser('remove_old_kernels')
    parser.add_argument('-k', '--keep', type=keep_type, default=1,
                        help='The number of kernel versions to keep')

    parser.add_argument('-y', '--yes', action='store_const', const='-y',
                        default='', help='Automatic yes to apt-get prompts')

    return parser.parse_args()


args = parse_args()
current = uname()[2]
versions = sorted(filter(lambda x: x != current, kernel_versions()),
                  key=cmp_to_key(cmp_version))
if not versions:
    exit(0)

keep = args.keep - 1
if LooseVersion(versions[-1]) > LooseVersion(current):
    versions = versions[:-1]
    if keep > 0:
        keep -= 1

if keep > 0:
    versions = versions[:-keep]

if versions:
    print('''The following kernel versions will be removed:
  %s
''' % '\n  '.join(versions))

    system('apt-get remove --purge %s %s' % (
        args.yes, ' '.join(packages(versions))))

    system('apt-get autoremove --purge %s' % args.yes)