[gentoo-user] Semi OT: hotplug / coldplug / udev ...

[gentoo-user] Semi OT: hotplug / coldplug / udev ...

[Arnau Bria]

Hi,

this is a general question about GNU/Linux.

I have some doubts about the way hotplug / coldplug / udev work.

I mean, some distros do not use hotplug (I'm not sure if it's basic
in gentoo) and are able to plug a (i.e) pendrive and kernel detects it,
udev creates its device, someone mounts it, etc... 

An my question is that. What really happen when you plug a (again,
i.e.) pendrive in your computer? Which programs take care in that
process? What about kernel?

Sorry if you fell spammed, but I do not find a good guide for
dummies :-)


Cheers!
-- 
Arnau Bria
http://blog.emergetux.net
Wiggum: Dispara a las ruedas Lou.
Lou: eee, es un tanque jefe.
Wiggum: Me tienes hartito con todas tus excusas.
-- 
gentoo-user@gentoo.org mailing list

Re: [gentoo-user] Semi OT: hotplug / coldplug / udev ...

[Boyd Stephen Smith Jr.]

On Thursday 09 November 2006 10:01, Arnau Bria <arnau@emergetux.net> wrote 
about '[gentoo-user] Semi OT: hotplug / coldplug / udev ...':
> I have some doubts about the way hotplug / coldplug / udev work.
>
> What really happen when you plug a (again,
> i.e.) pendrive in your computer? Which programs take care in that
> process? What about kernel?

Here's my understanding, I'm sure others will correct me, and possibly 
exapnd on it:

First, there's either a HW interrupt or the kernel scans the bus and sees a 
new device.  Then, the kernel queries the device and populates /sys (and 
possibly /proc) and notifies udev. udev is responsible for loading the 
appropriate module, if not already loaded, and creating the device nodes.

In the past, hotplug and coldplug where responsible for loading the module, 
and devfs would create device nodes under control of the module.  Neither 
hotplug nor coldplug are required with recent udev (w/ module loading 
support).  Hotplug and/or coldplug can provide module loading for early 
versions of udev (in addition to their role with devfs).

In ancient times, device nodes had to be created by the user (static /dev), 
possibly in response to kernel events (put that would require a module for 
the kernel hooks) or en masse for all possible devices.  One 
(dis?)advantage to static /dev was that device nodes would persist across 
reboots, which does not happen under devfs or udev -- unless your distro. 
provided /dev tarballs (ala Gentoo) or another method to save /dev on 
shutdown and restore it on startup.

-- 
"If there's one thing we've established over the years,
it's that the vast majority of our users don't have the slightest
clue what's best for them in terms of package stability."
-- Gentoo Developer Ciaran McCreesh
-- 
gentoo-user@gentoo.org mailing list

Re: [gentoo-user] Semi OT: hotplug / coldplug / udev ...

[Arnau Bria]

On Thu, 9 Nov 2006 10:57:02 -0600
Boyd Stephen Smith Jr. wrote:

> On Thursday 09 November 2006 10:01, Arnau Bria <arnau@emergetux.net>
> wrote about '[gentoo-user] Semi OT: hotplug / coldplug / udev ...':
> > I have some doubts about the way hotplug / coldplug / udev work.
> >
> > What really happen when you plug a (again,
> > i.e.) pendrive in your computer? Which programs take care in that
> > process? What about kernel?
> 
> Here's my understanding, I'm sure others will correct me, and
> possibly exapnd on it:

Thanks for your explanation. Things get clearer.

[...]

-- 
Arnau Bria
http://blog.emergetux.net
Wiggum: Dispara a las ruedas Lou.
Lou: eee, es un tanque jefe.
Wiggum: Me tienes hartito con todas tus excusas.
-- 
gentoo-user@gentoo.org mailing list

Re: [gentoo-user] Semi OT: hotplug / coldplug / udev ...

[Mark Shields]

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On 11/9/06, Arnau Bria <arnau@emergetux.net> wrote:
>
> Hi,
>
> this is a general question about GNU/Linux.
>
> I have some doubts about the way hotplug / coldplug / udev work.
>
> I mean, some distros do not use hotplug (I'm not sure if it's basic
> in gentoo) and are able to plug a (i.e) pendrive and kernel detects it,
> udev creates its device, someone mounts it, etc...
>
> An my question is that. What really happen when you plug a (again,
> i.e.) pendrive in your computer? Which programs take care in that
> process? What about kernel?
>
> Sorry if you fell spammed, but I do not find a good guide for
> dummies :-)
>
>
> Cheers!
> --
> Arnau Bria
> http://blog.emergetux.net
> Wiggum: Dispara a las ruedas Lou.
> Lou: eee, es un tanque jefe.
> Wiggum: Me tienes hartito con todas tus excusas.
> --
> gentoo-user@gentoo.org mailing list
>
>
Ivman is what you want to get the 'automounting' accomplished

# esearch ivman
[ Results for search key : ivman ]
[ Applications found : 1 ]

*  sys-apps/ivman
      Latest version available: 0.6.12
      Latest version installed: 0.6.12
      Size of downloaded files: 914 kB
      Homepage:    http://ivman.sf.net
      Description: Daemon to mount/unmount devices, based on info from HAL
      License:     GPL-2 QPL

It works for automounting cds, dvds, and should work for pendrives (although
I have yet to get it automounting a pendrive under a user account)

-- 
- Mark Shields

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Re: [gentoo-user] Semi OT: hotplug / coldplug / udev ...

[Neil Bothwick]

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On Tue, 14 Nov 2006 14:45:32 -0500, Mark Shields wrote:

> Ivman is what you want to get the 'automounting' accomplished

Unless you use KDE, which has its own automounting for removable storage.

> It works for automounting cds, dvds, and should work for pendrives
> (although I have yet to get it automounting a pendrive under a user
> account)

Is your user a member of the plugdev group? Automounting won't work
otherwise.


-- 
Neil Bothwick

Bus: (n.) a connector you plug money into, something like a slot machine.

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Re: [gentoo-user] Semi OT: hotplug / coldplug / udev ...

[Mick]

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On Tuesday 14 November 2006 20:23, Neil Bothwick wrote:
> On Tue, 14 Nov 2006 14:45:32 -0500, Mark Shields wrote:
> > Ivman is what you want to get the 'automounting' accomplished
>
> Unless you use KDE, which has its own automounting for removable storage.
>
> > It works for automounting cds, dvds, and should work for pendrives
> > (although I have yet to get it automounting a pendrive under a user
> > account)
>
> Is your user a member of the plugdev group? Automounting won't work
> otherwise.

Hmm . . .
=====================================================
A security policy in place prevents this sender from sending this message to 
this recipient, see message bus configuration file (rejected message had 
interface "org.freedesktop.Hal.Device.Volume" member "Mount" error 
name "(unset)" destination "org.freedesktop.Hal")
=====================================================
That's what comes up when I click on the USB pen drive on media:/

PS. This is without ivman, only hald.
-- 
Regards,
Mick

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Re: [gentoo-user] Semi OT: hotplug / coldplug / udev ...

[Neil Bothwick]

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On Wed, 15 Nov 2006 08:24:12 +0000, Mick wrote:

> > Is your user a member of the plugdev group? Automounting won't work
> > otherwise.  
> 
> Hmm . . .
> =====================================================
> A security policy in place prevents this sender from sending this
> message to this recipient, see message bus configuration file (rejected
> message had interface "org.freedesktop.Hal.Device.Volume" member
> "Mount" error name "(unset)" destination "org.freedesktop.Hal")
> =====================================================
> That's what comes up when I click on the USB pen drive on media:/

Which is pretty much what you'd expect it to say if your user is not a
member of the correct group.

If you were a member of plugdev, KDE would pop up a window when it
detected the device.


-- 
Neil Bothwick

I don't know what your problem is, but I'll bet it's hard to pronounce.

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Re: [gentoo-user] Semi OT: hotplug / coldplug / udev ...

[Mick]

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On Wednesday 15 November 2006 13:18, Neil Bothwick wrote:
> On Wed, 15 Nov 2006 08:24:12 +0000, Mick wrote:
> > > Is your user a member of the plugdev group? Automounting won't work
> > > otherwise.
> >
> > Hmm . . .
> > =====================================================
> > A security policy in place prevents this sender from sending this
> > message to this recipient, see message bus configuration file (rejected
> > message had interface "org.freedesktop.Hal.Device.Volume" member
> > "Mount" error name "(unset)" destination "org.freedesktop.Hal")
> > =====================================================
> > That's what comes up when I click on the USB pen drive on media:/
>
> Which is pretty much what you'd expect it to say if your user is not a
> member of the correct group.
>
> If you were a member of plugdev, KDE would pop up a window when it
> detected the device.

Thank you Neil.  For some reason it won't automount a usb CF here, let alone 
pop up windows:
===========================================
# cat /etc/group | grep hald
disk:x:6:root,adm,haldaemon
floppy:x:11:root,haldaemon
cdrom:x:19:michael,haldaemon
cdrw:x:80:haldaemon
usb:x:85:haldaemon
haldaemon:x:440:haldaemon
plugdev:x:441:haldaemon,michael
===========================================
-- 
Regards,
Mick

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Re: [gentoo-user] Semi OT: hotplug / coldplug / udev ...

[Arnau Bria]

On Tue, 14 Nov 2006 14:45:32 -0500
Mark Shields wrote:

> On 11/9/06, Arnau Bria <arnau@emergetux.net> wrote:

Hi Mark,

> Ivman is what you want to get the 'automounting' accomplished
Well, maybe I did expressed my question correctly, but I was not
looking for a "automounter", just wondering how
udev/hotplug/coldplug/hal/kernel works together...

anyway, thanks for your reply!
cheers!

-- 
Arnau Bria
http://blog.emergetux.net
Wiggum: Dispara a las ruedas Lou.
Lou: eee, es un tanque jefe.
Wiggum: Me tienes hartito con todas tus excusas.
-- 
gentoo-user@gentoo.org mailing list

Re: [gentoo-user] Semi OT: hotplug / coldplug / udev ...

[Mark Shields]

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On 11/15/06, Arnau Bria <arnau@emergetux.net> wrote:
>
> On Tue, 14 Nov 2006 14:45:32 -0500
> Mark Shields wrote:
>
> > On 11/9/06, Arnau Bria <arnau@emergetux.net> wrote:
>
> Hi Mark,
>
> > Ivman is what you want to get the 'automounting' accomplished
> Well, maybe I did expressed my question correctly, but I was not
> looking for a "automounter", just wondering how
> udev/hotplug/coldplug/hal/kernel works together...
>
> anyway, thanks for your reply!
> cheers!
>
> --
> Arnau Bria
> http://blog.emergetux.net
> Wiggum: Dispara a las ruedas Lou.
> Lou: eee, es un tanque jefe.
> Wiggum: Me tienes hartito con todas tus excusas.
> --
> gentoo-user@gentoo.org mailing list
>
>
Your question was "What really happen when you plug a (again, i.e.) pendrive
in your computer? Which programs take care in that process?" I was replying
with what program -- at least, the program I use -- does this.

-- 
- Mark Shields

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