How to invoke sudo password request in Python

Question

I've got a USB GPIO electronic gizmo attached to a desktop PC running Linux Mint 17 "Mate"; in this environment the gizmo appears as /dev/ttyACM0. I've written a GUI Python 2.7/Tkinter program to control the gizmo via the pySerial module. The program works when run from the console using sudo.

Being a GUI program, I want to be able to run it from the "Mate" desktop - but I can't, because being a serial device, accessing the gizmo requires root privileges obtained via sudo, wot has to be invoked at a Terminal.

# here's the offending code
import serial
numa = serial.Serial("/dev/ttyACM0", 19200, timeout=1)
....

How do I invoke the "Enter your password..." routine from within the Python program so a raw user doesn't have to open a Terminal to enter the password?

Thanks for any advice you can provide!

Finwood · Accepted Answer · 2015-04-04 10:17:14Z

1

I can't answer your question, but instead I'm going to solve your problem.

When you list the device file, you'll see something like this:

$ ls -l /dev/ttyACM0
crw-rw---- 1 root dialout 188, 0 Apr  4 11:22 /dev/ttyACM0

Both the owner (root) and the owner group (dialout) have read-write-access (rw-), while everybody else isn't able to access the device (---). Therefore, instead of giving the program root access to your system, you can simply add the user(s) to the dialout group:

$ sudo usermod -aG dialout <username>

Logging out and back in will be necessary, but afterwards your script will be able to both read and write to the serial interface without the need of a root password.

edited Apr 4, 2015 at 10:17

answered Apr 4, 2015 at 9:37

Finwood

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2 Comments

Andy Over a year ago

Thanks for taking the time to answer, Finwood; your solution worked well. I do wonder about security: in order to gain simple access to one device (a USB GPIO module) this solution removes the stricture that comes with accessing serial devices in general.

Finwood Over a year ago

Yes, this enables general access to serial devices. But is it really a security issue?

Rolf of Saxony · Accepted Answer · 2016-06-17 18:22:56Z

1

Use gksudo rather than sudo

from subprocess import call
call('gksudo -D "Program requires root priveledge \nSudo "your command here",shell=True)

for example:

call('gksudo -D "Override Sudo message " cp /etc/hosts /home/new.hosts',shell=True)

edited Jun 17, 2016 at 18:22

answered Jun 6, 2016 at 7:54

Rolf of Saxony

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