X-Git-Url: https://www.chiark.greenend.org.uk/ucgi/~ianmdlvl/git?p=elogind.git;a=blobdiff_plain;f=README;h=591e03a057a96a0d244ba5e3978c42b43f642c70;hp=2cde586ce23ddcc0ec15cc0b653cf6b7fb18d240;hb=11a421dab5ab4bf9b40464a64b81c9d5c282f414;hpb=01618658fd82dbc5e6315b639f00e87c6fee3c54

diff --git a/README b/README
index 2cde586ce..591e03a05 100644
--- a/README
+++ b/README
@@ -1,45 +1,67 @@
 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
+/dev/.udev/ is private to udev.
 
 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.
+  - Version 2.6.25 of the Linux kernel with sysfs, procfs, signalfd, inotify,
+    unix domain sockets, networking and hotplug enabled:
+      CONFIG_HOTPLUG=y
+      CONFIG_UEVENT_HELPER_PATH=""
+      CONFIG_NET=y
+      CONFIG_UNIX=y
+      CONFIG_SYSFS=y
+      CONFIG_SYSFS_DEPRECATED*=n
+      CONFIG_PROC_FS=y
+      CONFIG_TMPFS=y
+      CONFIG_INOTIFY=y
+      CONFIG_SIGNALFD=y
+      CONFIG_TMPFS_POSIX_ACL=y (user ACLs for device nodes)
+      CONFIG_BLK_DEV_BSG=y (SCSI tape devices)
 
-  - 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.)
+  - For reliable operation, the kernel must not use the CONFIG_SYSFS_DEPRECATED*
+    option.
+
+  - Unix domain sockets (CONFIG_UNIX) as a loadable kernel module 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 system must have the following group names resolvable at udev startup:
+      disk, cdrom, floppy, tape, audio, video, lp, tty, dialout, kmem.
+    Especially in LDAP setups, it is required, that getgrnam() is able to resolve
+    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
   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.
+  - 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,
     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.
+  - 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.
 
   - 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