udev rule for unmount action

udev rule for unmount action

[Christian Schmitt]

Hi,

I am trying to write a udev rule for my external HD that needs some special 
"care" when being unmounted (see here: 
http://elliotli.blogspot.com/2009/01/safely-remove-usb-hard-drive-in-
linux.html).
The problem is that I can not find a way to make udev react on the unmount 
command and execute a script. The "ACTION=remove" rule only works when I 
unplug the device. Is there a way to execute a script when unmounting? I guess 
doing this on the DE level is not the best way to go.

Cheers,
Chris

Re: udev rule for unmount action

[Marco d'Itri]

On Jun 06, Christian Schmitt <chris@ilovelinux.de> wrote:

> unplug the device. Is there a way to execute a script when unmounting? I guess 
> doing this on the DE level is not the best way to go.
The approved method is using inotify(2) on /proc/mounts, which is not
related to udev.

-- 
ciao,
Marco

Re: udev rule for unmount action

[Christian Schmitt]

On Saturday 06 June 2009 18:27:26 Marco d'Itri wrote:

> The approved method is using inotify(2) on /proc/mounts, which is not
> related to udev.

Thanks for this hint. As I am not too familiar with how to best implement it, 
can you give me a direction or an example for it? Is something like this 
already available somewhere? I did not find it.

Thanks
Chris

Re: udev rule for unmount action

[Karel Zak]

On Sat, Jun 06, 2009 at 06:27:26PM +0200, Marco d'Itri wrote:
> On Jun 06, Christian Schmitt <chris@ilovelinux.de> wrote:
> 
> > unplug the device. Is there a way to execute a script when unmounting? I guess 
> > doing this on the DE level is not the best way to go.
> The approved method is using inotify(2) on /proc/mounts, which is not
> related to udev.

 /proc and inotify are not good friends, but you can use poll() / select()

    Karel

-- 
 Karel Zak  <kzak@redhat.com>

Re: udev rule for unmount action

[Christian Schmitt]

On Monday 08 June 2009 14:38:26 Karel Zak wrote:

>
>  /proc and inotify are not good friends, but you can use poll() / select()
>
>     Karel

Sorry, but I do not want to write a C program, but a script. So I'd need a way 
to accomplish the detection of an unmount event in the script. As I'm using 
HAL there should be a way to do it without using inotify manually on 
/proc/mounts.

Chris

Re: udev rule for unmount action

[David Zeuthen]

Hi,

On Sat, 2009-06-06 at 17:02 +0200, Christian Schmitt wrote:
> Hi,
> 
> I am trying to write a udev rule for my external HD that needs some special 
> "care" when being unmounted (see here: 
> http://elliotli.blogspot.com/2009/01/safely-remove-usb-hard-drive-in-
> linux.html).

That's a very interesting blog entry, thanks for sharing. My experience
dealing with the storage stack in GNOME is that people keep asking for
this feature.

> The problem is that I can not find a way to make udev react on the unmount 
> command and execute a script. The "ACTION=remove" rule only works when I 
> unplug the device. Is there a way to execute a script when unmounting? I guess 
> doing this on the DE level is not the best way to go.

Actually I think doing this on the desktop level is the way forward.
There are two problems here.

First, consider a USB optical drive attached to the system. A typical
thing you want to do here is to eject the disc so you can insert another
one. Now, to eject media you first have to unmount it before you can
send the eject ioctl to the device. But if you hook into the unmount
process then you unbind the device before it is mounted and you never
get to send the eject ioctl.

The other example is when the user manually wants to unmount a partition
instead of ejecting it. Now, in the Nautilus file manager we do default
to ejecting stuff (the eject icon in the sidebar) but the user can also
right-click and click on Unmount in the context menu. If you hook into
the unmount process then the device(s) actually disappears, much against
what the user wanted.

Anyway, it's not a problem to do all this from the desktop level and I
just added support for this. 

First, I wrote a patch to DeviceKit-disks (the successor to HAL for
handling storage devices) that offers a DriveDetach() method and also
a :drive-can-detach property. Right now we only set :drive-can-detach
for USB devices but we can add support for other connection fabrics as
needed. The patch is here

http://cgit.freedesktop.org/DeviceKit/DeviceKit-disks/commit/?id[7350df8b63cf4178a2fe69ee740b5222130421

Then I added support for this in GVfs which is what Nautilus uses.

http://git.gnome.org/cgit/gvfs/commit/?id'b14622b7fcc228ddd617ebd723751ccd8dadaa
http://git.gnome.org/cgit/gnome-disk-utility/commit/?id÷6001f6f6beca8b21ff81e70f2633c60783479f
(actually GVfs uses gnome-disk-utility which is a "binding" of some sort
of DeviceKit-disks. But that's unimportant for this discussion.)

So, in a nutshell, GNOME 2.28 will support powering down USB enclosures
out of the box.

Btw, another change I made is to only unbind the usb-storage driver to
better handle multifunction devices. E.g. you don't want to unbind
drivers from all the USB interfaces.

Cheers,
David

Re: udev rule for unmount action

[Christian Schmitt]

On Tuesday 09 June 2009 02:45:57 David Zeuthen wrote:

Hi David,

> That's a very interesting blog entry, thanks for sharing. My experience
> dealing with the storage stack in GNOME is that people keep asking for
> this feature.

... and KDE users obviously, too ;-)

> Actually I think doing this on the desktop level is the way forward.
> There are two problems here.
>
> First, consider a USB optical drive attached to the system. A typical
> thing you want to do here is to eject the disc so you can insert another
> one. Now, to eject media you first have to unmount it before you can
> send the eject ioctl to the device. But if you hook into the unmount
> process then you unbind the device before it is mounted and you never
> get to send the eject ioctl.
>
> The other example is when the user manually wants to unmount a partition
> instead of ejecting it. Now, in the Nautilus file manager we do default
> to ejecting stuff (the eject icon in the sidebar) but the user can also
> right-click and click on Unmount in the context menu. If you hook into
> the unmount process then the device(s) actually disappears, much against
> what the user wanted.

Perfectly right. And that is why it would make sense IMHO to let the user 
specify special treatment for certain devices (like it is possible with udev 
rules (serial number, manufactor, model....)).
Actually, I am asking myself if the eject command is sufficient in this case of 
a certain external HD device that seems to need some more commands to go into 
suspend mode. That's why I think it would make more sense not to hard-wire 
certain detach/supend/spindown commands, but make them selectable for every 
device. Well, just some brainstorming. :-)


> Anyway, it's not a problem to do all this from the desktop level and I
> just added support for this.

As you seem to be a GNOME guy, I'll probably have to wait until someone starts 
to integrate DeviceKit support into Solid. Are you aware of any work in this 
direction?

Thanks for your effort.

Cheers,
Chris