X-Git-Url: http://www.chiark.greenend.org.uk/ucgi/~ianmdlvl/git?p=elogind.git;a=blobdiff_plain;f=README;h=00acf97c27e5405b5974a4c373b80f8113e17767;hp=6fa3a28b36e08e5a41dcb0bffc4c6f070f0087c3;hb=661a0bea80d129d5df708e36dbaed745c9d8392e;hpb=0fba212217eba2fee944583a54ef66f532459fc0 diff --git a/README b/README index 6fa3a28b3..00acf97c2 100644 --- a/README +++ b/README @@ -1,61 +1,91 @@ - -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. - -- 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 - -- 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, and it's a bit beyond proof of concept -code. Help is very much appreciated, see the TODO file for a list of -things left to be done. - -If you want to build using klibc, use the Makefile.klibc file: - - read the klibc/klibc/klibc/README file for how to set up the linux - symlink properly. - - make clean - - make -f Makefile.klibc -and marvel at the tiny binary you just created :) - -Any comment/questions/concerns please let me know. - -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 has complex dependencies and differs from distro + to distro. All major distros depend on udev these days and the system may not + work without a properly installed version. The upstream udev project does not + recommend to replace a distro's udev installation with the upstream version. + +Requirements: + - Version 2.6.18 of the Linux kernel for reliable operation of this release of + udev. The kernel may have a requirement on udev too, see Documentation/Changes + in the kernel source tree for the actual dependency. + + - The kernel must have sysfs, unix domain sockets and networking enabled. + (unix domain sockets (CONFIG_UNIX) as a loadable kernel module may work, + but it does not make any sense - 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 locations are supported by udev. + + +Operation: + Udev creates and removes device nodes in /dev, based on events the kernel + sends out on device discovery or removal. + + - Very 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 old hotplug helper /sbin/hotplug should be disabled on bootup, before + actions like loading kernel modules are taken, which may cause a lot of + events. + + - The udevd daemon must be started on bootup to receive netlink uevents + from the kernel driver core. + + - 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. + 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 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, may 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. + + - Default udev rules and persistent device naming rules are required by other + software that depends on the data udev collects 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@vger.kernel.org