X-Git-Url: http://www.chiark.greenend.org.uk/ucgi/~ianmdlvl/git?p=elogind.git;a=blobdiff_plain;f=README;h=fee078898cc2afaad3453bc8b22ceef18d810dcb;hp=07fa162bbd87d6f26e561f51b59d3fe4bac76d1e;hb=c249f66a70f9ea623205f27f7931727acbafba9e;hpb=cee360d32efd8392f7e342dcaeda1de50a2c1bcf

diff --git a/README b/README
index 07fa162bb..fee078898 100644
--- a/README
+++ b/README
@@ -1,37 +1,95 @@
+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 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.
 
-To use:
+  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.
 
-- Edit the udev.h file and replace the following variables with values
-  that make sense for your system:
-	#define UDEV_ROOT       "/udev/"
-	#define MKNOD           "/bin/mknod"
-  The only value most people will have to change is the UDEV_ROOT
-  variable, as I doubt you really want device nodes to be created in my
-  home directory :)
+Requirements:
+  - 2.6 version of the Linux kernel.
 
-- Run make to build the project.
+  - The kernel must have sysfs, netlink, and hotplug enabled.
 
-- Make sure sysfs is mounted.
+  - The proc filesystem must be mounted on /proc.
 
-- Point /proc/sys/kernel/hotplug at the location of the udev binary that
-  is created.  Then plug some block devices in, or other types of
-  devices that create dev files in sysfs.  An easy way to do this,
-  without any hardware is to use the scsi_debug module to create virtual
-  scsi devices.
+  - The sysfs filesystem must be mounted at /sys. No other location
+    is supported.
 
-- Watch as the nodes get created and removed.
 
+Operation:
+  - Udev creates and removes device nodes in /dev based on events
+    the kernel sends out on device discovery or removal
 
-Yes this is a really rough first cut, I know.  It's mostly a proof of
-concept that this can actually work.  See the TODO file for a list of
-things left to be done.
+  - Directly after mounting the root filesystem, the udevd daemon must be
+    started by an init script.
 
-Any comment/questions/concerns please let me know.
+  - From kernel version 2.6.15 on, the hotplug helper /sbin/hotplug should
+    be disabled with an init script before kernel modules are loaded.
+
+  - During bootup, /dev usually gets a tmpfs filesystem mounted which is
+    populated from scratch by udev (created nodes don't survive a reboot,
+    the /lib/udev/devices directory should be used for "static nodes").
+
+  - Udev replaces the hotplug event management invoked from /sbin/hotplug
+    by the udevd daemon, which receives the kernel events over netlink.
+
+  - All kernel events are matched against a set of specified rules which
+    make it possible to hook into the event processing.
+
+  - 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).
+
+Compile Options:
+  prefix
+  	Set this to the default root that you want to use only override
+  	this if you really know what you are doing even then, you probably
+  	don't do the right thing.
+  DESTDIR
+  	Prefix for 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.
+  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 program cdrom_id and scsi_id:
+  make EXTRAS="extras/cdrom_id extras/scsi_id"
+
+Installation:
+  - The install target intall 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.
+
+  - 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.
+
+Please direct any comment/question/concern to the linux-hotplug-devel mailing list at:
+  linux-hotplug-devel@lists.sourceforge.net
 
-greg k-h
-greg@kroah.com