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#!/usr/bin/env python3
# Copyright (C) 2007 Giampaolo Rodola' <g.rodola@gmail.com>.
# Use of this source code is governed by MIT license that can be
# found in the LICENSE file.
"""A basic unix daemon using the python-daemon library:
https://pypi.org/project/python-daemon.
Example usages:
$ python3 unix_daemon.py start
$ python3 unix_daemon.py stop
$ python3 unix_daemon.py status
$ python3 unix_daemon.py # foreground (no daemon)
$ python3 unix_daemon.py --logfile /var/log/ftpd.log start
$ python3 unix_daemon.py --pidfile /var/run/ftpd.pid start
This is just a proof of concept which demonstrates how to daemonize
the FTP server.
You might want to use this as an example and provide the necessary
customizations.
Parts you might want to customize are:
- UMASK, WORKDIR, HOST, PORT constants
- get_server() function (to define users and customize FTP handler)
Authors:
- Ben Timby - btimby <at> gmail.com
- Giampaolo Rodola' - g.rodola <at> gmail.com
"""
import argparse
import atexit
import os
import signal
import sys
import time
from pyftpdlib.authorizers import UnixAuthorizer
from pyftpdlib.filesystems import UnixFilesystem
from pyftpdlib.handlers import FTPHandler
from pyftpdlib.servers import FTPServer
# overridable options
HOST = ""
PORT = 21
PID_FILE = "/var/run/pyftpdlib.pid"
LOG_FILE = "/var/log/pyftpdlib.log"
WORKDIR = os.getcwd()
UMASK = 0
def pid_exists(pid):
"""Return True if a process with the given PID is currently running."""
try:
os.kill(pid, 0)
except PermissionError:
# EPERM clearly means there's a process to deny access to
return True
else:
return True
def get_pid():
"""Return the PID saved in the pid file if possible, else None."""
try:
with open(PID_FILE) as f:
return int(f.read().strip())
except FileNotFoundError:
pass
def stop():
"""Keep attempting to stop the daemon for 5 seconds, first using
SIGTERM, then using SIGKILL.
"""
pid = get_pid()
if not pid or not pid_exists(pid):
sys.exit("daemon not running")
sig = signal.SIGTERM
i = 0
while True:
sys.stdout.write('.')
sys.stdout.flush()
try:
os.kill(pid, sig)
except ProcessLookupError:
print(f"\nstopped (pid {pid})")
i += 1
if i == 25:
sig = signal.SIGKILL
elif i == 50:
sys.exit(f"\ncould not kill daemon (pid {pid})")
time.sleep(0.1)
def status():
"""Print daemon status and exit."""
pid = get_pid()
if not pid or not pid_exists(pid):
print("daemon not running")
else:
print(f"daemon running with pid {pid}")
sys.exit(0)
def get_server():
"""Return a pre-configured FTP server instance."""
handler = FTPHandler
handler.authorizer = UnixAuthorizer()
handler.abstracted_fs = UnixFilesystem
server = FTPServer((HOST, PORT), handler)
return server
def daemonize():
"""A wrapper around python-daemonize context manager."""
def _daemonize():
pid = os.fork()
if pid > 0:
# exit first parent
sys.exit(0)
# decouple from parent environment
os.chdir(WORKDIR)
os.setsid()
os.umask(0)
# do second fork
pid = os.fork()
if pid > 0:
# exit from second parent
sys.exit(0)
# redirect standard file descriptors
sys.stdout.flush()
sys.stderr.flush()
si = open(LOG_FILE)
so = open(LOG_FILE, 'a+')
se = open(LOG_FILE, 'a+', 0)
os.dup2(si.fileno(), sys.stdin.fileno())
os.dup2(so.fileno(), sys.stdout.fileno())
os.dup2(se.fileno(), sys.stderr.fileno())
# write pidfile
pid = str(os.getpid())
with open(PID_FILE, 'w') as f:
f.write(f"{pid}\n")
atexit.register(lambda: os.remove(PID_FILE))
pid = get_pid()
if pid and pid_exists(pid):
sys.exit(f'daemon already running (pid {pid})')
# instance FTPd before daemonizing, so that in case of problems we
# get an exception here and exit immediately
server = get_server()
_daemonize()
server.serve_forever()
def main():
global PID_FILE, LOG_FILE
USAGE = "python3 [-p PIDFILE] [-l LOGFILE]\n\n"
USAGE += "Commands:\n - start\n - stop\n - status"
parser = argparse.ArgumentParser(usage=USAGE)
parser.add_argument(
'-l', '--logfile', dest='logfile', help='the log file location'
)
parser.add_argument(
'-p',
'--pidfile',
dest='pidfile',
default=PID_FILE,
help='file to store/retrieve daemon pid',
)
parser.add_argument(
'command',
nargs='?',
help='command to execute: start, stop, restart, status',
)
options = parser.parse_args()
if options.pidfile:
PID_FILE = options.pidfile
if options.logfile:
LOG_FILE = options.logfile
if not options.command:
server = get_server()
server.serve_forever()
elif options.command == 'start':
daemonize()
elif options.command == 'stop':
stop()
elif options.command == 'restart':
try:
stop()
finally:
daemonize()
elif options.command == 'status':
status()
else:
sys.exit('invalid command')
if __name__ == '__main__':
sys.exit(main())
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