-
-udev - a userspace implementation of devfs
-
-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.
-
-- Make sure sysfs is mounted. udev will figure out where sysfs is mounted, but
- the traditional place for it is at /sys. You can mount it by hand by running:
- mount -t sysfs none /sys
-
-- Make sure you have the latest version of the linux-hotplug scripts. They are
- available at linux-hotplug.sf.net or from your local kernel.org mirror at:
- kernel.org/pub/linux/utils/kernel/hotplug/
- They are required in order for udev to work properly.
-
- If for some reason you do not install the hotplug scripts, you must tell the
- kernel to point the hotplug binary at wherever you install udev at. This can
- be done by:
- echo "/sbin/udev" > /proc/sys/kernel/hotplug
-
-- 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'.
- DEBUG - if set to 'true', debugging messages will be sent to the syslog
- as udev is run. Default value is 'false'.
- USE_DBUS - if set to 'true', DBUS messages will be sent everytime udev
- creates or removes a device node. This requires that DBUS
- development headers and libraries be present on your system to
- build properly. Default value is 'false'.
-
- So, if you want to build udev using klibc with debugging messages, you
- would do:
- make USE_KLIBC=true DEBUG=true
-
-
-- Install the project:
- make install
-
- This will put the udev binary in /sbin, create the /udev and /etc/udev
- directories, and place the udev configuration files in /etc/udev. You
- will probably want to edit the namedev.* 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 /udev/ based on the device types.
-
-- If you later get sick of it, uninstall it:
- make uninstall
-
-
-Things are still quite rough, and it's a bit beyond proof of concept
-code. Help is very much appreciated, see the TODO file for a list of
-things left to be done.
-
-If you want to build using klibc, use the Makefile.klibc file:
- - read the klibc/klibc/README file for how to set up the linux
- symlink properly.
- - make clean
- - make -f Makefile.klibc
-and marvel at the tiny binary you just created :)
-
-Any comment/questions/concerns please let me know.
-
-greg k-h
-greg@kroah.com
-
-
+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 depend on udev
+ these days 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.
+
+Requirements:
+ - 2.6.x version of the Linux kernel. See the RELEASE-NOTES file in the
+ udev tree and the Documentation/Changes in the kernel source tree for
+ the actual dependency.
+
+ - The kernel must have sysfs and unix domain socket enabled.
+ (unix domain sockets (CONFIG_UNIX) as a loadable kernel module may work,
+ but it is completely silly, don't complain if anything goes wrong.)
+
+ - The proc filesystem must be mounted on /proc.
+
+ - The sysfs filesystem must be mounted at /sys. No other location
+ will be supported by udev.
+
+
+Operation:
+ Udev creates and removes device nodes in /dev, based on events the kernel
+ sends out on device discovery or removal.
+
+ - Directly after mouting the real root filesystem, wherever that
+ happens, in initramfs or with a directly mounted root, /dev should get
+ a tmpfs filesystem mounted, which is populated from scratch by udev.
+ Created nodes or changed permissions don't survive a reboot.
+
+ - The content of /lib/udev/devices directory which contains the nodes,
+ symlinks and directories, which are always expected to be in/dev, should
+ be copied over to the tmpfs mounted /dev, to provide the required nodes
+ to initialize udev and continue booting.
+
+ - The udevd daemon must be started by an init script to receive netlink
+ events from the kernel driver core.
+
+ - From kernel version 2.6.15 on, the hotplug helper /sbin/hotplug should
+ be disabled with an init script before the boot scripts are run and
+ kernel modules are loaded.
+
+ - All kernel events are matched against a set of specified rules in
+ /etc/udev/rules.d/ which make it possible to hook into the event
+ processing to load required kernel modules and setup devices. For all
+ devices the kernel requests a device node, udev will create one with
+ the default name or the one specified by a matching udev rules.
+
+
+Compile Options:
+ prefix
+ Set this to the default root that you want to use. Only override
+ this if you really know what you are doing, even then, you probably
+ don't do the right thing.
+ DESTDIR
+ Prefix for install target, used for package building.
+ USE_LOG
+ If set to 'true', udev is able to pass errors or debug information
+ to syslog. This is very useful to see what udev is doing or not doing.
+ It is enabled by default, don't expect any useful answer, if you
+ need to hunt a bug, but you can't enable syslog.
+ DEBUG
+ If set to 'true', very verbose debugging messages will be compiled
+ into the udev binaries. The actual level of debugging is specified
+ in the udev config file.
+ STRIPCMD
+ If udev is compiled for packaging an empty string can be passed
+ to disable the stripping of the binaries.
+ 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 klibc.
+ Default value is 'false'. KLCC specifies the klibc compiler
+ wrapper, usually located at /usr/bin/klcc.
+ EXTRAS
+ If set, will build the "extra" helper programs as specified
+ as listed (see below for an example).
+
+If you want to build the udev helper programs:
+ make EXTRAS="extras/cdrom_id extras/scsi_id extras/volume_id"
+
+
+Installation:
+ - The install target intalls the udev binaries in the default locations,
+ All at boot time reqired binaries will be installed in /sbin.
+
+ - The default location for scripts and binaries that are called from
+ rules is /lib/udev. Other packages who install udev rules, should use
+ that diretory too.
+
+ - It is recommended to use the /lib/udev/devices directory to place
+ device nodes and symlinks in, which are copied to /dev at every boot.
+ That way, nodes for broken subsystems or devices which can't be
+ detected automatically by the kernel, will always be available.
+
+ - Copies of the rules files for all major distros are in the etc/udev
+ directory (you may look there how others distros are doing it).
+
+ - The persistent disk links in /dev/disk are the de facto standard
+ on Linux and should be installed with every default udev installation.
+ The devfs naming scheme rules are not recommended and not supported.
+
+Please direct any comment/question/concern to the linux-hotplug-devel mailing list at:
+ linux-hotplug-devel@lists.sourceforge.net
~ianmdlvl / elogind.git / blobdiff