Why do I get a 'permission denied' error when I try to access a serial device when executing python script on Jenkins? -


if execute following script user 'build' in command line works:

#!/usr/bin/python  import serial import pwd import os import grp  user = pwd.getpwuid(os.getuid()).pw_name print user  groups = [g.gr_name g in grp.getgrall() if user in g.gr_mem] gid = pwd.getpwnam(user).pw_gid groups.append(grp.getgrgid(gid).gr_name) print groups  print oct(os.stat("/dev/ttyusb0").st_mode & 0777)  ser = serial.serial('/dev/ttyusb0', 115200, timeout=1) print ser.portstr       # check port used ser.write("hello")      # write string ser.close() 

the output is

$ python test-serial.py build ['dialout', 'build'] 0660 /dev/ttyusb0 

if execute script in jenkins job get

[envinject] - loading node environment variables. building remotely on build-node in workspace /home/build/workspace/test-serial-python [test-serial-python] $ /bin/sh -xe /tmp/hudson7262474284926512955.sh + /usr/bin/python /home/build/test-serial.py build ['dialout', 'build'] 0660 traceback (most recent call last):   file "/home/build/test-serial.py", line 17, in <module>     ser = serial.serial('/dev/ttyusb0', 115200, timeout=1)   file "/usr/lib/python2.7/dist-packages/serial/serialutil.py", line 261, in __init__     self.open()   file "/usr/lib/python2.7/dist-packages/serial/serialposix.py", line 278, in open     raise serialexception("could not open port %s: %s" % (self._port, msg)) serial.serialutil.serialexception: not open port /dev/ttyusb0: [errno 13] permission denied: '/dev/ttyusb0' build step 'execute shell' marked build failure finished: failure 

if change file permissions sudo chmod 666 /dev/ttyusb0 jenkins job succeeds

[envinject] - loading node environment variables. building remotely on build-node in workspace /home/build/workspace/test-serial-python [test-serial-python] $ /bin/sh -xe /tmp/hudson9120277699281127818.sh + /usr/bin/python /home/build/test-serial.py build ['dialout', 'build'] 0666 /dev/ttyusb0 finished: success 

what problem here?

the solutions plain 'did try turn off , on again?'. build succeeded after restarting jenkins slave.

the reason added user 'build' group 'dialout' , after logout/login worked on command line. forgot reconnecting jenkins slave.

the output of python script showed correct group membership (because read database) not activated before reconnecting jenkins slave.


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