X-Git-Url: https://www.chiark.greenend.org.uk/ucgi/~ianmdlvl/git?p=elogind.git;a=blobdiff_plain;f=README;h=a76583ababfed3434e961a9c8a125b5c1e9e9033;hp=6fa3a28b36e08e5a41dcb0bffc4c6f070f0087c3;hb=0518da3b74a388680896747696b3644bbd3d98e5;hpb=0fba212217eba2fee944583a54ef66f532459fc0

diff --git a/README b/README
index 6fa3a28b3..a76583aba 100644
--- a/README
+++ b/README
@@ -1,61 +1,53 @@
+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 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.
 
-To use:
+Requirements:
+  - Version 2.6.19 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.
 
-- You must be running a 2.6 version of the Linux kernel.
+  - 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.)
 
-- 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
+  - The proc filesystem must be mounted on /proc/, the sysfs filesystem must
+    be mounted at /sys/. No other locations are supported by udev.
 
-- 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
+Operation:
+  Udev creates and removes device nodes in /dev/, based on events the kernel
+  sends out on device discovery or removal.
 
-- Build the project:
-	make
+  - 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.
 
-- Install the project:
-	make install
+  - 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.
 
-  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.
+  - 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.
 
-- 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
+  - 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
+    /lib/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.
 
+Please direct any comment/question/concern to the linux-hotplug mailing list at:
+  linux-hotplug@vger.kernel.org