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 recomend 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.
+ 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 2.6.22 of the Linux kernel for reliable operation of this release of
+ udev. The kernel must not use the CONFIG_SYSFS_DEPRECATED* option.
- - 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 kernel must have sysfs, unix domain sockets and networking enabled.
+ Unix domain sockets (CONFIG_UNIX) as a loadable kernel module is not
+ supported.
- - The proc filesystem must be mounted on /proc.
-
- - 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.
+ - The system must have the following group names resolvable at udev startup:
+ disk, cdrom, floppy, tape, audio, video, lp, tty, dialout, kmem.
+ Especially in LDAP setups, it is required, that getgrnam() is able to resolve
+ these group names with only the rootfs mounted, and while no network is
+ available.
Operation:
- Udev creates and removes device nodes in /dev, based on events the kernel
+ 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, the /dev directory should get a tmpfs
+ - 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,
+ - 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 exports a major/minor number, udev will create a
- device node with the default kernel name or the one specified by 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.
- 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
- 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
+Please direct any comment/question/concern to the linux-hotplug mailing list at:
+ linux-hotplug@vger.kernel.org
~ianmdlvl / elogind.git / blobdiff