-
-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.
-
- So, if you want to build udev using klibc with debugging messages, you
- would do:
- make USE_KLIBC=true DEBUG=true
-
- 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.
-
-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
+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 major distros depend on udev these
+ days and the system may not work without a proper installed version. The upstream
+ udev project does not support or recommend to replace a distro's udev installation
+ with the upstream version. The installation of a unmodified upstream version may
+ render your system unusable. Until now, there is no "default" setup or a set of
+ "default" rules provided by the upstream udev version.
+
+Requirements:
+ - Version 2.6.15 of the Linux kernel for reliable operation of this release of
+ udev. The kernel may have a requirement on udev too, see Documentation/Changes
+ in the kernel source tree for the actual dependency.
+
+ - The kernel must have sysfs, unix domain sockets and networking 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.
+
+ - Very early in the boot process, the /dev directory should get a 'tmpfs'
+ filesystem mounted, which is populated from scratch by udev. Created nodes
+ or changed permissions will not survive a reboot, which is intentional.
+
+ - 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 old hotplug helper /sbin/hotplug should be disabled on bootup, before
+ actions like loading kernel modules are taken, which may cause a lot of
+ events.
+
+ - The udevd daemon must be started on bootup to receive netlink uevents
+ from the kernel driver core.
+
+ - 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 exports a major/minor number, udev will create a
+ device node with the default kernel name or the one specified by a
+ matching udev rule.
+
+
+Compile Options:
+ DESTDIR
+ Prefix of 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.
+ USE_SELINUX
+ If set to 'true', udev will be built with SELinux support
+ enabled. This is disabled by default.
+ EXTRAS
+ list of helper programs in extras/ to build.
+ 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 /lib/udev or /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 directory 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 the major distros are provided as examples
+ in the etc/udev directory.
+
+ - The persistent device naming links in /dev/disk/ are required by other
+ software that depends on the data udev has collected from the devices
+ and should be installed by default with every udev installation.
+
+Please direct any comment/question/concern to the linux-hotplug-devel mailing list at:
+ linux-hotplug-devel@lists.sourceforge.net
~ianmdlvl / elogind.git / blobdiff