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Dynamic device management with Udev, HAL, and D-Bus

Conclusions

Just a couple of years ago, configuring new hardware on Linux was a daunting task and just one more reason for newcomers to keep clear. Now, Linux offers convenient device management that provides trouble-free, dynamic handling of devices plugged in at run time – including WLAN sticks, digital cameras, and even camcorders. Linux can listen on interfaces such as Bluetooth and Firewire and, if necessary, not only integrate a device you plug in, but launch the matching application as well.

Fortunately, the trend in recent months has been toward standardizing the underlying technologies. Udev has already clearly ousted its predecessor, Devfs, and found its way into the Linux kernel. Now the Freedesktop.org-sponsored team of HAL and D-Bus is establishing itself in the face of competition from the previous Gnome and KDE favorites, Corba and DCOP.

This merge has greatly improved communications between the two desktop environments. Gnome already has a mature front end for dynamic device management with Gnome Volume Manager and related tools. KDE is following suit after considerable restructuring of its libraries in version 4.

The KDE Solid hardware library adds a new and powerful framework to make hardware management on KDE easier than ever. In the months to come, you can look forward to more dynamic device management fireworks.

Glossar

Uevent: Short form of User Event. This means a notification event from the kernel to programs in userspace. This memory area, which is separate from the kernel space, is populated by normal programs and non-kernel subsystems. The Udev subsystem runs in userspace.
Sysfs: A virtual filesystem that was introduced with kernel version 2.6. It is normally accessible under /sys and makes device and driver information defined in the Kernel Device Model, the kernel's internal device database, available to programs in userspace.
IPC: Short for Interprocess Communication, a method of communication and data exchange between processes on the same computer.

Infos

Udev: http://www.kernel.org/pub/linux/utils/kernel/hotplug/udev.html
HAL: http://www.freedesktop.org/wiki/Software/hal
Freedesktop.org: http://www.freedesktop.org/wiki
D-Bus: http://www.freedesktop.org/wiki/Software/dbus
Corba: http://de.wikipedia.org/wiki/CORBA
DCOP: http://developer.kde.org/documentation/other/dcop.html
DCOM for programmers: http://msdn.microsoft.com/en-us/library/ms809311.aspx

The Author

Eric Amberg has worked for many years as a System Engineer for IT networks, specializing in Linux and network security for large corporations. On top of this, he has published books and articles on Linux. His latest book, Linux Servers with Debian GNU/Linux (German) was published in June 2007.

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