More on DBUS/HAL/UDEV

[Matthew Carpenter]

Here is a snippit I found immensely enlightening from one of the Ubuntu devs.  
Let me know if you're interested in more of the conversation, which centers 
around the desire for non-locking CD access (a la SuSE 9.1 with subfs), 
server automount (because the automount is not handled by this stack) and his 
responses.  I've "highlighted" the "udev/hal/dbus in a nutshell" section.

----------  Forwarded Message  ----------
<snip>

There is non-GUI solution for automounting - ivman. ivman is highly
configurable tool (please, check http://ivman.sourceforge.net/).

As for the server... If you are instaling server, you don't want hal, dbus
and automounter. You don't want supermount or subfs either. On server
administrator must have complete control over computer. Of course, there
are situations were users are able to insert CD in server and then access
it over Samba or something. That's what's ivman is great for.

As you can see, on every Ubuntu there are entrys for dvdrom/cdrom devices
in fstab. fstab is place where you define only devices that should mount
upon boot or you want them be mountable by user. gnome-volume-manager and
kio_media reads fstab and if there are some specific demands (readonly,
umask, etc...) they are obeyed. Of course, you can setup hal to sync
/etc/fstab, without a problem (man fstab-sync).

Yes, you can't eject CD if it's in use. If CD device is in use by some
kernel proces (nfs-kernel, e.g.) it will crash your system, cause of Linux
kernel's imperfections (being monolitic kernel). mount/umount is the only
right way to go, and if an application doesn't release CD device, then
that app has a nasty bug.

Joe-user can go to (gnome:) System -> Preferences -> Removable drives and
Media Preferences. Here he can setup (in hoary) default behaviuor for
certain devices. On breezy he can set-up even more; printers, scanners,
iPod, etc...

Crypto functions will be implemented soon in g-v-m. I don't know for other
managers, but I'm sure you can setup everything you can imagine with
ivman.
*_*_*_*_*_*_*_*_*_*_*_*_*_*_*_*_* Highlighting Important Stuff *_*_*_*_*_*_*_*
It's very simple. dbus discovers pluged devices, hotplug raises modules,
udev creates device, and hal notifies applications that communicate with
it. This isn't just for CD/floppy/etc. This is for a lot of stuff; mouse,
keyboard, printer, scanner...
*_*_*_*_*_*_*_*_*_*_*_*_*_*_*_*_*_*_*_*_*_*_*_*_*_*_*_*_*_*_*_*_*_*_*_*_*_*

Trust me, it's better then submount/subfs. I tried them all. From autofs
to SuSE's and Mandrake's subfs/supermount. They are all lightyears behind
this combination. This is rather new design and it has some flaws, but it
is a future for desktop systems. Server, well... Servers will allways be a
job for hands. I have a lot of servers (arround 30) and none of them has
dbus/hal. But all 100 desktops have them :).

-------------------------------------------------------

-- 
Matthew Carpenter 
matt at eisgr.com                          http://www.eisgr.com/

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