Remotely shutdown/restart a Linux machine without password

Question

I am writing a pyQt client-server application which restarts/shutdowns PCs remotely.
The receivers are listening to the network for incomming messages, and the sender sends a restart/shutdown message to the selected receiver.

The following part of code is running on a receiver:

import os

self.currentOS = calling a function to determine the current OS

if self.currentOS == "Win":
    os.system("shutdown -r -f -t 1")
elif self.currentOS == "Lin":
    os.system("shutdown -r now")

I have 2 virtual machines acting as receivers, one on Windows and the other on Linux.

When i send a restart message to the Windows receiver, the machine restarts.
When i send a restart message to the Linux receiver, it asks for password

Incoming:EXEC_OP_RESTART
[sudo] password for jwalker: 

What do i have to change to overcome this?
Is shutdown -r now the only way, or can i do this another way (more directly)?

EDIT: In this question, something called dbus was used, and it was done without a password, i am searching about dbus, as an alternative.

Answer 1

It takes root privileges to restart a Linux machine. Some desktop environments use a daemon to get around this.... but I suggest editing the sudoers file

https://help.ubuntu.com/community/Sudoers for a howto. Basically you'll want to allow the restart command - and only the restart command - to be run without a password.

Something like:

ALL ALL=(ALL) NOPASSWD: /usr/sbin/shutdown

will let any user on the machine restart it without using a password. You'll probably need to prefix the 'shutdown' in your system command with 'sudo', though it looks like it's being called automatically somehow. If this isn't secure enough, you can make a group, make your program run as that group, then allow that group to restart.

EDIT: Apparently this can be done with DBus (note: I haven't tested this):

dbus-send --system --print-reply --dest="org.freedesktop.Hal" /org/freedesktop/Hal/devices/computer org.freedesktop.Hal.Device.SystemPowerManagement.Restart int32:0

This works because dbus runs as root (or has root privs) and can therefore accept requests to restart from nonpriveleged processes and act on them. I still think the sudo way is cleaner, and so will anyone who maintains this code.

Answer 2

Run the script with sudo python. For example, if your file were named remotesd.py, sudo python remotesd.py