
udev - a userspace device manager

For more information on the design, and structure of this project, see the
files in the docs/ directory.

To use:

- You must be running a 2.6 version of the Linux kernel.

- Your 2.6 kernel must have had CONFIG_HOTPLUG enabled when it was built.

- Make sure sysfs is mounted at /sys. No other location is supported.
  You can mount it by running:
  	mount -t sysfs none /sys

- Make sure you integrate udev with your hotplug setup. There is a copy of
  the rules files for all major distros in the etc/udev folder. You may look
  there how others are doing it.

- Make sure you integrate with the kernel hotplug events. Later versions of
  udev are able to listen directly to a netlink socket, older versions used
  udevsend to feed the udev daemon with the kernel event. The most basic
  setup to run udev is to let the kernel for the udev binary directly:
	echo "/sbin/udev" > /proc/sys/kernel/hotplug

  While this may work in some setups, it is not recommended to do. A recent
  kernel and udev version is able to operate with the event serializing daemon
  udevd, that makes sure, that no "remove" event will beat a "add" event for
  the same device.

- Build the project:
	make

  Note:
      There are a number of different flags that you can use when building
      udev.  They are as follows:
	prefix
		set this to the default root that you want udev to be
		installed into.  This works just like the 'configure --prefix'
		script does.  Default value is ''.  Only override this if you
		really know what you are doing.
	USE_KLIBC
		if set to 'true', udev is built and linked against the
		included version of klibc.  Default value is 'false'.
	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.)
	USE_SELINUX
		if set to 'true', udev will be built with SELinux support
		enabled.  This is disabled by default.
	DEBUG
		if set to 'true', debugging messages will be sent to the syslog
		as udev is run.  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.)

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

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

      udev will follow the setting of the debug level in udev.conf. Adapt this
      value to see the debug in syslog.

- Install the project:
	make install

  This will put the udev binaries in /sbin, create the and /etc/udev
  directories, and place the udev configuration files in /etc/udev/.  You
  will probably want to edit the *.rules files to create custom naming
  rules.  More info on how the config files are set up are contained in
  comments in the files, and is located in the documentation.

- Add and remove devices from the system and marvel as nodes are created
  and removed in /dev based on the device types.

- If you later get sick of it, uninstall it:
	make uninstall

If nothing seems to happen, make sure your build worked properly by
running the udev-test.pl script as root in the test/ subdirectory of the
udev source tree. Running udevstart should populate an empty /dev
directory. You may test, if a node is recreated after running udevstart.

Development and documentation help is very much appreciated, see the TODO
file for a list of things left to be done.

Any comment/questions/concerns please let me and the other udev developers
know by sending a message to the linux-hotplug-devel mailing list at:
	linux-hotplug-devel@lists.sourceforge.net

greg k-h
greg@kroah.com

