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#!/usr/bin/env python3
"""systemctl: subset of systemctl used for image construction
Mask/preset systemd units
"""
import argparse
import fnmatch
import os
import re
import sys
from collections import namedtuple
from pathlib import Path
version = 1.0
ROOT = Path("/")
SYSCONFDIR = Path("etc")
BASE_LIBDIR = Path("lib")
LIBDIR = Path("usr", "lib")
class SystemdFile():
"""Class representing a single systemd configuration file"""
def __init__(self, root, path):
self.sections = dict()
self._parse(root, path)
def _parse(self, root, path):
"""Parse a systemd syntax configuration file
Args:
path: A pathlib.Path object pointing to the file
"""
skip_re = re.compile(r"^\s*([#;]|$)")
section_re = re.compile(r"^\s*\[(?P<section>.*)\]")
kv_re = re.compile(r"^\s*(?P<key>[^\s]+)\s*=\s*(?P<value>.*)")
section = None
if path.is_symlink():
try:
path.resolve()
except FileNotFoundError:
# broken symlink, try relative to root
path = root / Path(os.readlink(str(path))).relative_to(ROOT)
with path.open() as f:
for line in f:
if skip_re.match(line):
continue
line = line.rstrip("\n")
m = section_re.match(line)
if m:
section = dict()
self.sections[m.group('section')] = section
continue
while line.endswith("\\"):
line += f.readline().rstrip("\n")
m = kv_re.match(line)
k = m.group('key')
v = m.group('value')
if k not in section:
section[k] = list()
section[k].extend(v.split())
def get(self, section, prop):
"""Get a property from section
Args:
section: Section to retrieve property from
prop: Property to retrieve
Returns:
List representing all properties of type prop in section.
Raises:
KeyError: if ``section`` or ``prop`` not found
"""
return self.sections[section][prop]
class Presets():
"""Class representing all systemd presets"""
def __init__(self, scope, root):
self.directives = list()
self._collect_presets(scope, root)
def _parse_presets(self, presets):
"""Parse presets out of a set of preset files"""
skip_re = re.compile(r"^\s*([#;]|$)")
directive_re = re.compile(r"^\s*(?P<action>enable|disable)\s+(?P<unit_name>(.+))")
Directive = namedtuple("Directive", "action unit_name")
for preset in presets:
with preset.open() as f:
for line in f:
m = directive_re.match(line)
if m:
directive = Directive(action=m.group('action'),
unit_name=m.group('unit_name'))
self.directives.append(directive)
elif skip_re.match(line):
pass
else:
sys.exit("Unparsed preset line in {}".format(preset))
def _collect_presets(self, scope, root):
"""Collect list of preset files"""
locations = [SYSCONFDIR / "systemd"]
# Handle the usrmerge case by ignoring /lib when it's a symlink
if not BASE_LIBDIR.is_symlink():
locations.append(BASE_LIBDIR / "systemd")
locations.append(LIBDIR / "systemd")
presets = dict()
for location in locations:
paths = (root / location / scope).glob("*.preset")
for path in paths:
# earlier names override later ones
if path.name not in presets:
presets[path.name] = path
self._parse_presets([v for k, v in sorted(presets.items())])
def state(self, unit_name):
"""Return state of preset for unit_name
Args:
presets: set of presets
unit_name: name of the unit
Returns:
None: no matching preset
`enable`: unit_name is enabled
`disable`: unit_name is disabled
"""
for directive in self.directives:
if fnmatch.fnmatch(unit_name, directive.unit_name):
return directive.action
return None
def collect_services(root):
"""Collect list of service files"""
locations = [SYSCONFDIR / "systemd"]
# Handle the usrmerge case by ignoring /lib when it's a symlink
if not BASE_LIBDIR.is_symlink():
locations.append(BASE_LIBDIR / "systemd")
locations.append(LIBDIR / "systemd")
services = dict()
for location in locations:
paths = (root / location / "system").glob("*")
for path in paths:
if path.is_dir():
continue
# implement earlier names override later ones
if path.name not in services:
services[path.name] = path
return services
def add_link(path, target):
try:
path.parent.mkdir(parents=True)
except FileExistsError:
pass
if not path.is_symlink():
print("ln -s {} {}".format(target, path))
path.symlink_to(target)
def process_deps(root, config, service, location, prop, dirstem):
systemdir = SYSCONFDIR / "systemd" / "system"
target = ROOT / location.relative_to(root)
try:
for dependent in config.get('Install', prop):
wants = root / systemdir / "{}.{}".format(dependent, dirstem) / service
add_link(wants, target)
except KeyError:
pass
def enable(root, service, location, services):
if location.is_symlink():
# ignore aliases
return
config = SystemdFile(root, location)
template = re.match(r"[^@]+@(?P<instance>[^\.]*)\.", service)
if template:
instance = template.group('instance')
if not instance:
try:
instance = config.get('Install', 'DefaultInstance')[0]
service = service.replace("@.", "@{}.".format(instance))
except KeyError:
pass
if instance is None:
return
else:
instance = None
process_deps(root, config, service, location, 'WantedBy', 'wants')
process_deps(root, config, service, location, 'RequiredBy', 'requires')
try:
for also in config.get('Install', 'Also'):
enable(root, also, services[also], services)
except KeyError:
pass
systemdir = root / SYSCONFDIR / "systemd" / "system"
target = ROOT / location.relative_to(root)
try:
for dest in config.get('Install', 'Alias'):
alias = systemdir / dest
add_link(alias, target)
except KeyError:
pass
def preset_all(root):
presets = Presets('system-preset', root)
services = collect_services(root)
for service, location in services.items():
state = presets.state(service)
if state == "enable" or state is None:
enable(root, service, location, services)
def mask(root, *services):
systemdir = root / SYSCONFDIR / "systemd" / "system"
for service in services:
add_link(systemdir / service, "/dev/null")
def main():
if sys.version_info < (3, 4, 0):
sys.exit("Python 3.4 or greater is required")
parser = argparse.ArgumentParser()
parser.add_argument('command', nargs=1, choices=['mask', 'preset-all'])
parser.add_argument('service', nargs=argparse.REMAINDER)
parser.add_argument('--root')
parser.add_argument('--preset-mode',
choices=['full', 'enable-only', 'disable-only'],
default='full')
args = parser.parse_args()
root = Path(args.root) if args.root else ROOT
command = args.command[0]
if command == "mask":
mask(root, *args.service)
elif command == "preset-all":
if len(args.service) != 0:
sys.exit("Too many arguments.")
if args.preset_mode != "enable-only":
sys.exit("Only enable-only is supported as preset-mode.")
preset_all(root)
else:
raise RuntimeError()
if __name__ == '__main__':
main()
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