udev - userspace device management

For more information see the files in the docs/ directory.

Important Note:
  Integrating udev in the system is a whole lot of work, has complex dependencies
  and differs a lot from distro to distro. All reasonable distros use udev these
  days, the major ones make it mandatory and the system will not work without it.

  The upstream udev project does not support or recomend to replace a distro's udev
  installation with the upstream version. The installation of a unmodified upstream
  version may render your system unusable! There is no "default" setup or a set
  of "default" rules provided by the upstream udev version.

udev requires:
  - 2.6 version of the Linux kernel

  - the kernel must have sysfs, netlink, and hotplug enabled

  - proc must be mounted on /proc

  - sysfs must be mounted at /sys, no other location is supported

  - udev creates and removes device nodes in /dev based on events
    the kernel sends out on device discovery or removal

  - during bootup /dev usually gets a tmpfs mounted which is populated scratch
    by udev (created nodes don't survive a reboot, it always starts from scratch)

  - udev replaces the hotplug event management invoked from /sbin/hotplug
    by the udevd daemon, which receives the kernel events over netlink

  - all kernel events are matched against a set of specified rules which
    make it posible to hook into the event processing

  - there is a copy of the rules files for all major distros in the etc/udev
    directory (you may look there how others distros are doing it)

Setting which are used for building udev:
  prefix
  	set this to the default root that you want to use
  	Only override this if you really know what you are doing
  DESTDIR
  	prefix for install target for package building
  USE_LOG
  	if set to 'true', udev will emit messages to the syslog when
  	it creates or removes device nodes.  This is helpful to see
  	what udev is doing.  This is enabled by default.  Note, if you
  	are building udev against klibc it is recommended that you
  	disable this option (due to klibc's syslog implementation.)
  DEBUG
  	if set to 'true', verbose debugging messages will be compiled into
  	the udev binaries.  Default value is 'false'.
  USE_SELINUX
  	if set to 'true', udev will be built with SELinux support
  	enabled.  This is disabled by default.
  USE_KLIBC
  	if set to 'true', udev is built and linked against the
  	included version of klibc.  Default value is 'false'.
  KERNEL_DIR
  	If this is not set it will default to /lib/modules/`uname -r`/build
  	This is used if USE_KLIBC=true to find the kernel include
  	directory that klibc needs to build against.  This must be set
  	if you are not building udev while running a 2.6 kernel.
  EXTRAS
  	if set, will build the "extra" helper programs as specified
  	as listed (see below for an example.)

if you want to build udev using klibc with debugging messages:
  make USE_KLIBC=true DEBUG=true

if you want to build the udev helper program cdrom_id and scsi_id:
  make EXTRAS="extras/cdrom_id extras/scsi_id"

Please direct any comment/question/concern to the linux-hotplug-devel mailing list at:
  linux-hotplug-devel@lists.sourceforge.net

