+udev - userspace device management
-udev - a userspace implementation of devfs
+For more information see the files in the docs/ directory.
-For more information on the design, and structure of this project, 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 use udev these
+ days, the major ones make it mandatory and the system will not work without it.
-To use:
+ 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.
-- Edit the udev.h file and replace the following variables with values
- that make sense for your system:
- #define SYSFS_ROOT "/sys"
- #define UDEV_ROOT "/home/greg/linux/udev/"
- #define DEV_FILE "/dev"
- #define MKNOD "/bin/mknod"
- The only value most people will have to change is the UDEV_ROOT
- variable, as I doubt you really want device nodes to be created in my
- home directory :)
+udev requires:
+ - 2.6 version of the Linux kernel
-- Run make to build the project.
+ - the kernel must have sysfs, netlink, and hotplug enabled
-- Make sure sysfs is mounted.
+ - proc must be mounted on /proc
-- Point /proc/sys/kernel/hotplug at the location of the udev binary that
- is created. Then plug some block devices in, or other types of
- devices that create dev files in sysfs. An easy way to do this,
- without any hardware is to use the scsi_debug module to create virtual
- scsi devices.
+ - sysfs must be mounted at /sys, no other location is supported
-- Watch as the nodes get created and removed.
+ - 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)
-Yes this is a really rough first cut, I know. It's mostly a proof of
-concept that this can actually work. See the TODO file for a list of
-things left to be done.
+ - udev replaces the hotplug event management invoked from /sbin/hotplug
+ by the udevd daemon, which receives the kernel events over netlink
-Any comment/questions/concerns please let me know.
+ - all kernel events are matched against a set of specified rules which
+ make it posible 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)
+
+Setting which are used for building udev:
+ prefix
+ set this to the default root that you want to use
+ Only override this if you really know what you are doing
+ DESTDIR
+ prefix for install target 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. Note, if you
+ are building udev against klibc it is recommended that you
+ disable this option (due to klibc's syslog implementation.)
+ DEBUG
+ if set to 'true', verbose debugging messages will be compiled into
+ the udev binaries. Default value is 'false'.
+ 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 the
+ included version of klibc. 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.
+ EXTRAS
+ if set, will build the "extra" helper programs as specified
+ as listed (see below for an example.)
+
+if you want to build udev using klibc with debugging messages:
+ make USE_KLIBC=true DEBUG=true
+
+if you want to build the udev helper program cdrom_id and scsi_id:
+ make EXTRAS="extras/cdrom_id extras/scsi_id"
+
+Please direct any comment/question/concern to the linux-hotplug-devel mailing list at:
+ linux-hotplug-devel@lists.sourceforge.net
-greg k-h
-greg@kroah.com
~ianmdlvl / elogind.git / blobdiff