X-Git-Url: https://www.chiark.greenend.org.uk/ucgi/~ianmdlvl/git?p=elogind.git;a=blobdiff_plain;f=README;h=19ed4468eab0806207bacf6f27dc3f606413789a;hp=1a46a3c1eebf6b0d96d7b21bee77326badecb83c;hb=c2df8b5f517216ab7763c1b25655c170cfcee097;hpb=d2ce1817117daa9523b1572523f1e7684bae779f

diff --git a/README b/README
index 1a46a3c1e..19ed4468e 100644
--- a/README
+++ b/README
@@ -1,39 +1,77 @@
+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 use udev these
+  days, the major ones make it mandatory 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 SYSFS_ROOT      "/sys"
-	#define UDEV_ROOT       "/home/greg/linux/udev/"
-	#define DEV_FILE        "/dev"
-	#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 :)
+udev requires:
+  - 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.
+  - proc 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.
+  - sysfs must be mounted at /sys, no other location is supported
 
-- Watch as the nodes get created and removed.
+  - udev creates and removes device nodes in /dev based on events
+    the kernel sends out on device discovery or removal
 
+  - during bootup /dev usually gets a tmpfs mounted which is populated scratch
+    by udev (created nodes don't survive a reboot, it always starts from scratch)
 
-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.
+  - udev replaces the hotplug event management invoked from /sbin/hotplug
+    by the udevd daemon, which receives the kernel events over netlink
 
-Any comment/questions/concerns please let me know.
+  - all kernel events are matched against a set of specified rules which
+    make it posible to hook into the event processing
+
+  - there is a copy of the rules files for all major distros in the etc/udev
+    directory (you may look there how others distros are doing it)
+
+Setting which are used for building udev:
+  prefix
+  	set this to the default root that you want to use
+  	Only override this if you really know what you are doing
+  DESTDIR
+  	prefix for install target for package building
+  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.)
+  DEBUG
+  	if set to 'true', verbose debugging messages will be compiled into
+  	the udev binaries.  Default value is 'false'.
+  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 the
+  	included version of klibc.  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.
+  EXTRAS
+  	if set, will build the "extra" helper programs as specified
+  	as listed (see below for an example.)
+
+if you want to build udev using klibc with debugging messages:
+  make USE_KLIBC=true DEBUG=true
+
+if you want to build the udev helper program cdrom_id and scsi_id:
+  make EXTRAS="extras/cdrom_id extras/scsi_id"
+
+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