X-Git-Url: http://www.chiark.greenend.org.uk/ucgi/~ianmdlvl/git?p=elogind.git;a=blobdiff_plain;f=README;h=21a6c186dc91292d5bf000fcade7be2ef7e9a9ab;hp=c0475dc9048a017a265bca0cdc32180ec02aa350;hb=d992629180a4bbce84c28456057bf4e9c6bfce6e;hpb=057f2bdbf65ba6276209869feb74097d73c06b99 diff --git a/README b/README index c0475dc90..21a6c186d 100644 --- a/README +++ b/README @@ -1,94 +1,109 @@ - -udev - a userspace implementation of devfs - -For more information on the design, and structure of this project, see the -files in the docs/ directory. - -To use: - -- You must be running a 2.6 version of the Linux kernel. - -- Your 2.6 kernel must have had CONFIG_HOTPLUG enabled when it was built. - -- Make sure sysfs is mounted. udev will figure out where sysfs is mounted, but - the traditional place for it is at /sys. You can mount it by hand by running: - mount -t sysfs none /sys - -- Make sure you have the latest version of the linux-hotplug scripts. They are - available at linux-hotplug.sf.net or from your local kernel.org mirror at: - kernel.org/pub/linux/utils/kernel/hotplug/ - They are required in order for udev to work properly. - - If for some reason you do not install the hotplug scripts, you must tell the - kernel to point the hotplug binary at wherever you install udev at. This can - be done by: - echo "/sbin/udev" > /proc/sys/kernel/hotplug - -- Build the project: - make - - Note: - There are a number of different flags that you can use when building - udev. They are as follows: - prefix - set this to the default root that you want udev to be - installed into. This works just like the 'configure --prefix' - script does. Default value is ''. Only override this if you - really know what you are doing. - USE_KLIBC - if set to 'true', udev is built and linked against the - included version of klibc. Default value is 'false'. - 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.) - USE_SELINUX - if set to 'true', udev will be built with SELinux support - enabled. This is disabled by default. - DEBUG - if set to 'true', debugging messages will be sent to the syslog - as udev is run. 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. - - So, if you want to build udev using klibc with debugging messages, you - would do: - make USE_KLIBC=true DEBUG=true - -- Install the project: - make install - - This will put the udev binary in /sbin, create the /udev and /etc/udev - directories, and place the udev configuration files in /etc/udev. You - will probably want to edit the namedev.* files to create custom naming - rules. More info on how the config files are set up are contained in - comments in the files, and is located in the documentation. - -- Add and remove devices from the system and marvel as nodes are created - and removed in /udev/ based on the device types. - -- If you later get sick of it, uninstall it: - make uninstall - - -Things are still quite rough, but it should work properly. If nothing -seems to happen, make sure your build worked properly by running the -udev-test.pl script as root in the test/ subdirectory of the udev source -tree. - -Development and documentation help is very much appreciated, see the TODO -file for a list of things left to be done. - - -Any comment/questions/concerns please let me and the other udev developers -know by sending a message to the linux-hotplug-devel mailing list at: - linux-hotplug-devel@lists.sourceforge.net - -greg k-h -greg@kroah.com +udev - userspace device management + +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 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. + +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. + + - 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 proc filesystem must be mounted on /proc. + + - The sysfs filesystem must be mounted at /sys. No other location + will be supported by udev. + + +Operation: + 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, /dev 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, + 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. + + - 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. + + - 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 + processing to load required kernel modules and setup devices. For all + devices the kernel requests a device node, udev will create one with + the default name or the one specified by a matching udev rules. + + +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. + 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 programs: + 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 /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 all major distros are in the etc/udev + directory (you may look there how others distros are doing it). + + - The persistent disk links in /dev/disk are the de facto standard + on Linux and should be installed with every default udev installation. + The devfs naming scheme rules are not recommended and not supported. + +Please direct any comment/question/concern to the linux-hotplug-devel mailing list at: + linux-hotplug-devel@lists.sourceforge.net