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.
+ Integrating udev in the system has complex dependencies and differs from distro
+ to distro. All major distros depend on udev these days and the system may not
+ work without a properly installed version. The upstream udev project does not
+ recommend to replace a distro's udev installation with the upstream 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.
+ - Version 2.6.18 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 and unix domain socket enabled.
+ - 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.
+ but it does not make any sense - don't complain if anything goes wrong.)
- - The sysfs filesystem must be mounted at /sys. No other location
- will be supported by udev.
+ - The proc filesystem must be mounted on /proc, the sysfs filesystem must
+ be mounted at /sys. No other locations are supported by udev.
Operation:
Udev creates and removes device nodes in /dev, based on events the kernel
sends out on device discovery or removal.
- - Early in the boot process, /dev 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.
+ - 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 udevd daemon must be started by an init script to receive netlink
- uevents from the kernel driver core.
+ - 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.
- - From kernel version 2.6.15 on, the hotplug helper /sbin/hotplug should
- be disabled with an init script 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
+ /lib/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.
+ 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:
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"
+ 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 /sbin.
+ All 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
+ rules is /lib/udev. Other packages who install udev rules, may use
that directory too.
- - It is recommended to use the /lib/udev/devices directory to place
+ - 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.
+ - Default udev rules and persistent device naming rules are required by other
+ software that depends on the data udev collects 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
+ linux-hotplug@vger.kernel.org
~ianmdlvl / elogind.git / blobdiff