Udev

udev is a file system replacement for DEVFS on the Linux 2.6 Kernel (computer science) series. Its primary function is managing device nodes in Filesystem Hierarchy Standard.

=New features in udev=

Unlike the traditional system of managing devices in Linux, which used a static set of device nodes, udev dynamically provides nodes for only the devices actually present on a system. Although devfs also provided such functionality, advocates for udev cited a number of reasons for preferring its implementation over devfs:[http://kernel.org/pub/linux/utils/kernel/hotplug/udev_vs_devfs]

*udev is independent of major and minor device numbers, whereas devfs did not address the need for dynamic device numbers *Unlike devfs, udev supports giving devices persistent names, which do not depend on, for example, the order in which the devices are plugged into the system. *udev executes in user space, as opposed to devfs kernel space. One consequence is that udev moves naming policy out of the kernel. *udev is smaller and unlike devfs, complies with the Linux Standard Base naming system. *According to some developers, devfs suffered from lack of maintenance and contained unfixable design flaws and Race_condition.

=Operation=

udev allows for rules that specify what device name is given to a specific device, regardless of which port (computing) it is plugged into. For example, a rule to always mount a hard drive with manufacturer iRiver and device code ABC as /dev/iriver is possible. This consistent naming of devices guarantees that Scripting programming languages dependent on a specific device s existence will not be broken.

udev works by receiving /sbin/hotplug calls sent by the kernel whenever a device is added or removed from the system.

=Authors=

udev was developed by Greg Kroah-Hartman in collaboration with Dan Stekloff, Kay Sievers, and many others.

=External links=

*[http://www.reactivated.net/writing_udev_rules.html Discussion of udev rules] *[http://www.kernel.org/pub/linux/utils/kernel/hotplug/udev-FAQ udev FAQ] *[http://www.gentoo.org/doc/en/udev-guide.xml The Gentoo udev Guide]