+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 depend on udev
+ these days 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 :)
+Requirements:
+ - 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.
+ - The proc filesystem 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.
+ - The sysfs filesystem must be mounted at /sys. No other location
+ is supported.
-- Watch as the nodes get created and removed.
+Operation:
+ - Udev creates and removes device nodes in /dev based on events
+ the kernel sends out on device discovery or removal
-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.
+ - Directly after mounting the root filesystem, the udevd daemon must be
+ started by an init script.
-Any comment/questions/concerns please let me know.
+ - 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.
+
+ - All kernel events are matched against a set of specified rules which
+ make it possible to hook into the event processing.
+
+ - 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).
+
+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 even then, you probably
+ don't do the right thing.
+ DESTDIR
+ Prefix for 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.
+ 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.
+ 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 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
-greg k-h
-greg@kroah.com
~ianmdlvl / elogind.git / blobdiff