Under the impression of loosing some really important data because of a damaged partition table on a USB flash drive I am developing a backup strategy for my system.
I know myself and so I decided that I need to automate this. While trying to figure out how one can run a script as soon as a specific drive is mounted, I came across DeviceKit. It’s the planned replacement of HAL and is used in Ubuntu Karmic. Udev is not an option for me, because I don’t want to mess around with mounting myself (and I hate running stuff as root…).
So here is what I found out about using DBus and DeviceKit in Python:
import dbus bus = dbus.SystemBus() proxy = bus.get_object("org.freedesktop.DeviceKit.Disks", "/org/freedesktop/DeviceKit/Disks") iface = dbus.Interface(proxy, "org.freedesktop.DeviceKit.Disks") #enumerates all devices print iface.EnumerateDevices() #gets the device kit path of a specific device path = iface.FindDeviceByDeviceFile("/dev/sdc1") #= "/org/freedesktop/DeviceKit/Disks/devices/sdc" #gets an object representing the device specified by the path device = bus.get_object("org.freedesktop.DeviceKit.Disks", path) #prints some XML that shows you the available methods, signals and properties print device.Introspect() #gets a proxy for getting properties device_prop = dbus.Interface(device, "org.freedesktop.DBus.Properties") #you need to specify an interface (properties could be ambiguous) print device_prop.Get("org.freedesktop.DeviceKit.Disks.Device", "device-mount-paths") #gets a proxy you can call methods on device_iface = dbus.Interface(device, "org.freedesktop.DeviceKit.Disks.Device") #unmounts the partition device_iface.FilesystemUnmount(dbus.Array([], 's'))
The DBus API of DeviceKit is documented here.
Now we want to be notified when a drive is mounted:
import dbus import gobject from dbus.mainloop.glib import DBusGMainLoop def device_added_callback(device): print 'Device %s was added' % (device) def device_changed_callback(device): print 'Device %s was changed' % (device) #must be done before connecting to DBus DBusGMainLoop(set_as_default=True) bus = dbus.SystemBus() proxy = bus.get_object("org.freedesktop.DeviceKit.Disks", "/org/freedesktop/DeviceKit/Disks") iface = dbus.Interface(proxy, "org.freedesktop.DeviceKit.Disks") #addes two signal listeners iface.connect_to_signal('DeviceAdded', device_added_callback) iface.connect_to_signal('DeviceChanged', device_changed_callback) #start the main loop mainloop = gobject.MainLoop() mainloop.run()
A typical output when a flash drive is plugged in looks like this:
Device /org/freedesktop/DeviceKit/Disks/devices/sdc was added Device /org/freedesktop/DeviceKit/Disks/devices/sdc1 was added Device /org/freedesktop/DeviceKit/Disks/devices/sdc1 was changed
With this knowledge I’m currently working on a little python script that runs in background and executes a shell script when a file system is mounted. I’ll post it, when it’s finished 
