New submission from Tjeerd Pinkert <t.j.pink...@alumnus.utwente.nl>:
If I use os.setgid and os.setuid to switch to an other user in some daemon code, I cannot open the serial port anymore. If I run the same code directly from the user I can open the serial port. Since the serial module is using the open() call to open the serial device I wonder if the mistake is in the serial module or in the os module. see also: https://sourceforge.net/tracker/?func=detail&aid=3081643&group_id=46487&atid=446302 Sample code showing the behaviour using the daemon module from: http://hathawaymix.org/Software/Sketches/daemon.py (and no it's not this module, also my own crappy code did the same thing and gives the same erroneous behaviour) ------------------------ #!/usr/bin/python """Test daemon""" import daemon import logging import time import serial import os class HelloDaemon(daemon.Daemon): default_conf = 'test.conf' section = 'test' def setup_user(self): print os.getuid(), os.getgid() ser=serial.Serial(0) print ser.portstr ser.close() def run(self): while True: logging.info('The daemon says hello') time.sleep(1) if __name__ == '__main__': HelloDaemon().main() ----------------------------------------- now make the config file: -------------------------------- [test] uid = gid = pidfile = ./hellodaemon.pid logfile = ./hellodaemon.log loglevel = info ---------------------- when I run it as my own user it works fine, e.g.: t...@machine$ ./test.py 1000 1000 /dev/ttyS0 it nicely opens the port. if I fill in tjp for uid and gid in the configfile and run it as: t...@machine$ sudo ./test.py 1000 1000 Traceback (most recent call last): File "./test.py", line 26, in <module> HelloDaemon().main() File "/home/tjp/tmp/pydaemon/daemon.py", line 121, in main self.start() File "/home/tjp/tmp/pydaemon/daemon.py", line 196, in start self.setup_user() File "./test.py", line 17, in setup_user ser=serial.Serial(0) File "/usr/lib/python2.6/dist-packages/serial/serialutil.py", line 166, in __init__ self.open() File "/usr/lib/python2.6/dist-packages/serial/serialposix.py", line 175, in open raise SerialException("could not open port %s: %s" % (self._port, msg)) serial.serialutil.SerialException: could not open port 0: [Errno 13] Permission denied: '/dev/ttyS0' I hope someone with more experience can either help me out, or confirm if this should be regarded a bug, and then in which module, os or serial Yours, Tjeerd ---------- components: Extension Modules messages: 118033 nosy: Tjeerd.Pinkert priority: normal severity: normal status: open title: os.setuid and os.setgid have unexpected influence on serial module versions: Python 2.6 _______________________________________ Python tracker <rep...@bugs.python.org> <http://bugs.python.org/issue10032> _______________________________________ _______________________________________________ Python-bugs-list mailing list Unsubscribe: http://mail.python.org/mailman/options/python-bugs-list/archive%40mail-archive.com
