Python SIGTERM not killing subprocess

Question

I have a class which can start and close a process. However it seems not to close the process.

My python code, there are other methods but they work fine.:

class KismetInstance:
    """Creates a kismet_server instance"""

    def __init__(self, value=False):
        logging.basicConfig(format='%(asctime)-15s::: %(message)s')
        self.logger = logging.getLogger('kismet_instance')
        self.example = value

    def __create_kismet_instance__(self):
        """
        Create a kismet_server subprocess.
        :return:
        """
        shell = ['sudo', '/usr/local/bin/kismet_server']
        self.logger.debug('Attempting to run: %s', " ".join(shell))
        self.kismet = Popen(shell, stdin=PIPE, stdout=PIPE, stderr=PIPE, cwd=r'./logs', preexec_fn=os.setsid)


    def __destroy_kismet_instance__(self):
        """
        Kill the subprocess
        :return:
        """
        os.killpg(os.getpgid(self.kismet.pid), 15)

It can create the subprocess fine. But I get this error when I try to kill (no sudo)

OSError: [Errno 1] Operation not permitted

And if I run with sudo, the process is still running afterwards.

pi@raspberrypi ~/project $ ps -A | grep 'kismet'
 2912 ?        00:00:00 kismet_server

Answer 1

I managed to fix this. Turns out the subprocess was respawning itself creating something weird which prevented python from keeping track of it.

So I had to do this to fix it, However this is not the most elegant solution, and rather dangerouddangerous .

Be careful if you use this , because if you enter a term more broad than mine ( 'kismet' ) then you could kill a lot of processes on your system.

def __destroy_kismet_instance__(self):
        """
        Kill the subprocess
        :return:
        """
        sig = signal.SIGKILL # What signal to send
        os.killpg(os.getpgid(self.kismet.pid), sig) # Kill one of them
        p_list = subprocess.Popen(['ps', '-A'], stdout=subprocess.PIPE) # Get All processes on system
        out, err = p_list.communicate()
        for line in out.splitlines(): # For each line (or process)
            if 'kismet' in line: # if 'kismet' appears in its name
                pid = int(line.split(None, 1)[0]) # Get the process ID
                self.logger.debug("Found: %d", pid)
                os.killpg(os.getpgid(pid), sig) # Kill the process