X-Git-Url: https://www.chiark.greenend.org.uk/ucgi/~ianmdlvl/git?p=elogind.git;a=blobdiff_plain;f=README;h=664457de0f9b2f5cfe2dbfca2b07a15e22fa272c;hp=b4c0ee051faa4f014b6fb454ea7b999d2326b7db;hb=1230d021bd75de9b1503bbaa807d6a59789963db;hpb=89eaa6a56eded9f76c452e20994aaf45c7c2dad9 diff --git a/README b/README index b4c0ee051..664457de0 100644 --- a/README +++ b/README @@ -8,11 +8,11 @@ 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, + - 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="" @@ -22,18 +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. @@ -46,29 +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