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 use udev these
- days, the major ones make it mandatory and the system will not work without it.
+ 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.
-udev requires:
- - 2.6 version of the Linux kernel
+Requirements:
+ - 2.6 version of the Linux kernel.
- - the kernel must have sysfs, netlink, and hotplug enabled
+ - The kernel must have sysfs, netlink, and hotplug enabled.
- - proc must be mounted on /proc
+ - The proc filesystem must be mounted on /proc.
- - sysfs must be mounted at /sys, no other location is supported
+ - The sysfs filesystem must be mounted at /sys. No other location
+ is supported.
- - udev creates and removes device nodes in /dev based on events
+
+Operation:
+ - Udev creates and removes device nodes in /dev based on events
the kernel sends out on device discovery or removal
- - during bootup /dev usually gets a tmpfs mounted which is populated scratch
- by udev (created nodes don't survive a reboot, it always starts from scratch)
+ - Directly after mounting the root filesystem, the udevd daemon must be
+ started by an init script.
+
+ - From kernel version 2.6.15 on, the hotplug helper /sbin/hotplug should
+ be disabled with an init script before kernel modules are loaded.
+
+ - During bootup, /dev usually gets a tmpfs filesystem mounted which is
+ populated from scratch by udev (created nodes don't survive a reboot,
+ the /lib/udev/devices directory should be used for "static nodes").
- - udev replaces the hotplug event management invoked from /sbin/hotplug
- by the udevd daemon, which receives the kernel events over netlink
+ - Udev replaces the hotplug event management invoked from /sbin/hotplug
+ by the udevd daemon, which receives the kernel events over netlink.
- - all kernel events are matched against a set of specified rules which
- make it posible to hook into the event processing
+ - All kernel events are matched against a set of specified rules which
+ make it possible to hook into the event processing.
- - there is a copy of the rules files for all major distros in the etc/udev
- directory (you may look there how others distros are doing it)
+ - 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).
-Setting which are used for building udev:
+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
+ 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 for package building
+ Prefix for install target, used for package building.
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.
+ 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.
DEBUG
- if set to 'true', verbose debugging messages will be compiled into
- the udev binaries. Default value is 'false'.
+ 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
+ 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.
+ If set to 'true', udev is built and linked against klibc.
Default value is 'false'. KLCC specifies the klibc compiler
- wrapper, usually in /usr/bin/klcc
+ 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 set, will build the "extra" helper programs as specified
+ as listed (see below for an example).
-if you want to build the udev helper program cdrom_id and scsi_id:
+If you want to build the udev helper program cdrom_id and scsi_id:
make EXTRAS="extras/cdrom_id extras/scsi_id"
+Installation:
+ - The install target intall 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.
+
+ - 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.
+
Please direct any comment/question/concern to the linux-hotplug-devel mailing list at:
linux-hotplug-devel@lists.sourceforge.net
~ianmdlvl / elogind.git / blobdiff