From a6c5b514d8e698316c57a0cf5183fcd8a7bc6d26 Mon Sep 17 00:00:00 2001 From: Kay Sievers Date: Mon, 31 Aug 2009 10:19:40 +0200 Subject: [PATCH 1/1] update README --- README | 33 +++++++++++++++++---------------- 1 file changed, 17 insertions(+), 16 deletions(-) diff --git a/README b/README index 591e03a05..f6d1ab525 100644 --- a/README +++ b/README @@ -8,8 +8,8 @@ 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. +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, @@ -25,16 +25,16 @@ Requirements: CONFIG_INOTIFY=y CONFIG_SIGNALFD=y CONFIG_TMPFS_POSIX_ACL=y (user ACLs for device nodes) - CONFIG_BLK_DEV_BSG=y (SCSI tape devices) + 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. @@ -47,29 +47,30 @@ Requirements: --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 -- 2.30.2