X-Git-Url: https://www.chiark.greenend.org.uk/ucgi/~ianmdlvl/git?p=elogind.git;a=blobdiff_plain;f=README;h=664457de0f9b2f5cfe2dbfca2b07a15e22fa272c;hp=d438afae4647b4f671751649fa99a3856cf73974;hb=1230d021bd75de9b1503bbaa807d6a59789963db;hpb=98ad80f8737b0cfcd264e32e37d6c5d4e35e4ea5

diff --git a/README b/README
index d438afae4..664457de0 100644
--- a/README
+++ b/README
@@ -1,15 +1,18 @@
 udev - userspace device management
 
-For more information see the files in the docs/ directory.
+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.
 
-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.
+Tools and rules shipped by udev are not public API and may change at any time.
+Never call any private tool in /lib/udev from any external application, it might
+just go away in the next release. Access to udev information is only offered
+by udevadm and libudev. Tools and rules in /lib/udev, and the entire content of
+the /dev/.udev directory is private to udev and does change whenever needed.
 
 Requirements:
-  - Version 2.6.25 of the Linux kernel with sysfs, procfs, signalfd, inotify,
+  - Version 2.6.27 of the Linux kernel with sysfs, procfs, signalfd, inotify,
     unix domain sockets, networking and hotplug enabled:
       CONFIG_HOTPLUG=y
       CONFIG_UEVENT_HELPER_PATH=""
@@ -19,18 +22,19 @@ Requirements:
       CONFIG_SYSFS_DEPRECATED*=n
       CONFIG_PROC_FS=y
       CONFIG_TMPFS=y
-      CONFIG_TMPFS_POSIX_ACL=y
-      CONFIG_INOTIFY=y
+      CONFIG_INOTIFY_USER=y
       CONFIG_SIGNALFD=y
+      CONFIG_TMPFS_POSIX_ACL=y (user ACLs for device nodes)
+      CONFIG_BLK_DEV_BSG=y (SCSI devices)
 
-  - For reliable operation, the kernel must not use the CONFIG_SYSFS_DEPRECATED*
+  - For reliable operations, the kernel must not use the CONFIG_SYSFS_DEPRECATED*
     option.
 
-  - Unix domain sockets (CONFIG_UNIX) as a loadable kernel module is not
-    supported.
+  - Unix domain sockets (CONFIG_UNIX) as a loadable kernel module may work,
+    but it is not supported.
 
-  - The proc filesystem must be mounted on /proc/, the sysfs filesystem must
-    be mounted at /sys/. No other locations are supported by udev.
+  - The proc filesystem must be mounted on /proc, the sysfs filesystem must
+    be mounted at /sys. No other locations are supported by udev.
 
   - The system must have the following group names resolvable at udev startup:
       disk, cdrom, floppy, tape, audio, video, lp, tty, dialout, kmem.
@@ -38,30 +42,35 @@ Requirements:
     these group names with only the rootfs mounted, and while no network is
     available.
 
+  - To build all udev extras, libacl, libglib2, libusb, usbutils, pciutils,
+    gperf are needed. These dependencies can be disabled with the
+    --disable-extras option.
+
 Operation:
-  Udev creates and removes device nodes in /dev/, based on events the kernel
+  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'
+  - Early in the boot process, the /dev directory should get a 'tmpfs'
     filesystem mounted, which is maintained 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,
+  - 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 in the kernel
-    configuration, it is not needed, and may render the system unusable
-    because of a fork-bombing behavior.
+  - The deprecated hotplug helper /sbin/hotplug should be disabled in the
+    kernel configuration, it is not needed today, and may render the system
+    unusable because the kernel may create too many processes in parallel
+    so that the system runs out-of-memory.
 
   - 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
+    /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:
+Please direct any comment/question to the linux-hotplug mailing list at:
   linux-hotplug@vger.kernel.org