How can I run a command when a usb device is (dis-) connected?

Question

I am new to linux, and this is probably a noob question, so, sorry for that.

I am using a linux PC in my workshop, and I would like to automate the workshop. That's why I have installed a power strip where all my tools are plugged in to. That way it is easy to turn of all my tools all at ones.

I also have a usb-hub's power input plugged in there. When it is turned of, the pc detects it as disconnected. Can I use that information to automatically lock or suspend the PC when it is disconnected?

TLDR; Can I make a script that suspends the PC when a usb device is disconnected?

Run tail -f /var/log/syslog.log and try to connect/disconnect your USB device. — FedKad, Sep 22 '19 at 14:10

Jacob Vlijm · Answer 1 · 2019-09-23T17:51:34.313

Action on (dis) connecting usb device

The tiny script below will suspend the computer on the event of disconnecting a (any) usb volume.

#!/usr/bin/env python3
import gi
from gi.repository import GLib, Gio
import subprocess

class WatchOut:

    def __init__(self):
        someloop = GLib.MainLoop()
        self.setup_watching()
        someloop.run()

    def setup_watching(self):
        self.watchdrives = Gio.VolumeMonitor.get()
        # event to watch (see further below, "Other options")
        self.watchdrives.connect("volume_removed", self.actonchange)

    def actonchange(self, *args):
        # command to run (see further below, "Other options")
        subprocess.Popen(["systemctl", "suspend"])

WatchOut()

To use:

Copy the script into an empty file, save it as watchout.py
Run it in the background:
```
python3 /path/to/watchout.py
```
If all works as expected, run it from startup

Other options

In this script, obviously the signal on "volume_removed" is used. Other possible events:

"volume_added", "volume_removed", "mount_added", "mount_removed"

To make it perform other commands on event, replace the command in the line:

subprocess.Popen(["systemctl", "suspend"])

(command and args are set as a list, like ["systemctl", "suspend"])

EDIT - Only act on specifically named volumes

As mentioned in a comment, you'd prefer to only run a command on specifically named volumes. If you run the example below with one or more volumenames as arguments, action will be limited to only those volumes:

#!/usr/bin/env python3
import gi
from gi.repository import GLib, Gio
import subprocess
import sys

args = sys.argv[1:]

class WatchOut:

    def __init__(self):
        someloop = GLib.MainLoop()
        self.setup_watching()
        someloop.run()

    def setup_watching(self):
        self.watchdrives = Gio.VolumeMonitor.get()
        # event to watch (see further below, "Other options")
        self.watchdrives.connect("volume_removed", self.actonchange)

    def actonchange(self, event, volume):
        if volume.get_name() in args:
            # command to run (see further below, "Other options")
            subprocess.Popen(["systemctl", "suspend"])

WatchOut()

Usage

Is pretty much the same as the first one, just add the volumenames as arguments, e.g.

python3 /path/to/watchout.py <volumename_1> <volumename_2>

Hi! This seems really good! Thanks for the help, but I've got one question. Can I specify the volume to detect? — LenDuck24, Sep 23 '19 at 17:07
@LenDuck24 If e.g. name would be specific, absolutely! Just mention an example, I'll edit it in as an example. — Jacob Vlijm, Sep 23 '19 at 17:31

score 2 · Answer 2 · answered Sep 22 '19 at 14:32

Simple way to detect usb events is

 udevadm monitor --kernel --property --subsystem-match=usb

Programmatical approach: https://raw.githubusercontent.com/gavv/snippets/master/udev/udev_monitor_usb.c