X-Git-Url: http://www.chiark.greenend.org.uk/ucgi/~ianmdlvl/git?p=elogind.git;a=blobdiff_plain;f=README;h=7ac1d4509ccfbed7877e9efb2d3140d76da032d9;hp=a2ce9c7d367137853fcb242daa6a9ccde7dfb381;hb=cad4697469883b73cdd43e7e83db122951535ee8;hpb=57663b364beda200ec189c889e7d9c9fede37c9a diff --git a/README b/README index a2ce9c7d3..7ac1d4509 100644 --- a/README +++ b/README @@ -1,93 +1,103 @@ - -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 at /sys. You can mount it 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 *.rules 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 major distros depend on udev these + days and the system may not work without a proper installed version. 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. Until now, 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, the /dev directory 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 exports a major/minor number, udev will create a + device node with the default kernel name or the one specified by a + matching udev rule. + + +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. + 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 + list of helper programs in extras/ to build. + 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 /lib/udev or /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 the major distros are provided as examples + in the etc/udev directory. + + - The persistent device naming links in /dev/disk/ are required by other + software that depends on the data udev has collected from the devices + and should be installed by default with every udev installation. + +Please direct any comment/question/concern to the linux-hotplug-devel mailing list at: + linux-hotplug-devel@lists.sourceforge.net