1 udev - userspace device management
3 For more information see the files in the docs/ directory.
6 Integrating udev in the system is a whole lot of work, has complex dependencies
7 and differs a lot from distro to distro. All reasonable distros depend on udev
8 these days and the system will not work without it.
10 The upstream udev project does not support or recomend to replace a distro's udev
11 installation with the upstream version. The installation of a unmodified upstream
12 version may render your system unusable! There is no "default" setup or a set
13 of "default" rules provided by the upstream udev version.
16 - 2.6 version of the Linux kernel.
18 - The kernel must have sysfs, netlink, and hotplug enabled.
20 - The proc filesystem must be mounted on /proc.
22 - The sysfs filesystem must be mounted at /sys. No other location
27 - Udev creates and removes device nodes in /dev based on events
28 the kernel sends out on device discovery or removal
30 - Directly after mounting the root filesystem, the udevd daemon must be
31 started by an init script.
33 - From kernel version 2.6.15 on, the hotplug helper /sbin/hotplug should
34 be disabled with an init script before kernel modules are loaded.
36 - During bootup, /dev usually gets a tmpfs filesystem mounted which is
37 populated from scratch by udev (created nodes don't survive a reboot,
38 the /lib/udev/devices directory should be used for "static nodes").
40 - Udev replaces the hotplug event management invoked from /sbin/hotplug
41 by the udevd daemon, which receives the kernel events over netlink.
43 - All kernel events are matched against a set of specified rules which
44 make it possible to hook into the event processing.
46 - Copies of the rules files for all major distros are in the etc/udev
47 directory (you may look there how others distros are doing it).
51 Set this to the default root that you want to use only override
52 this if you really know what you are doing even then, you probably
53 don't do the right thing.
55 Prefix for install target, used for package building.
57 if set to 'true', udev is able to pass errors or debug information
58 to syslog. This is very useful to see what udev is doing or not doing,
59 it is enabled by default.
61 If set to 'true', very verbose debugging messages will be compiled
62 into the udev binaries. The actual level of debugging is specified
63 in the udev config file.
65 If udev is compiled for packaging an empty string can be passed
66 to disable the stripping of the binaries.
68 If set to 'true', udev will be built with SELinux support
69 enabled. This is disabled by default.
71 If set to 'true', udev is built and linked against klibc.
72 Default value is 'false'. KLCC specifies the klibc compiler
73 wrapper, usually located at /usr/bin/klcc.
75 If set, will build the "extra" helper programs as specified
76 as listed (see below for an example).
78 If you want to build the udev helper program cdrom_id and scsi_id:
79 make EXTRAS="extras/cdrom_id extras/scsi_id"
82 - The install target intall the udev binaries in the default locations,
83 all at boot time reqired binaries will be installed in /sbin.
85 - The default location for scripts and binaries that are called from
88 - It is recommended to use the /lib/udev/devices directory to place
89 device nodes and symlinks in, which are copied to /dev at every boot.
90 That way, nodes for broken subsystems or devices which can't be
91 detected automatically by the kernel will always be available.
93 Please direct any comment/question/concern to the linux-hotplug-devel mailing list at:
94 linux-hotplug-devel@lists.sourceforge.net