X-Git-Url: http://www.chiark.greenend.org.uk/ucgi/~ianmdlvl/git?p=elogind.git;a=blobdiff_plain;f=README;h=5a8d4cc0b3ea9ea8808bec0dd9327efe43a55eb3;hp=1eecf9d847e75e79c424269c0a9452ecff9e82c5;hb=092a53bb92165e189b2c14ab5e21481a85b23475;hpb=600b2584566a44b8a57f546f5ce27f5b1cce21d6 diff --git a/README b/README index 1eecf9d84..5a8d4cc0b 100644 --- a/README +++ b/README @@ -7,17 +7,22 @@ does not recommend replacing a distro's udev installation with the upstream version. The upstream udev project's set of default rules may require a most recent -kernel release to work properly. This is currently version 2.6.31. +kernel release to work properly. This is currently version 2.6.32. 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 contents of -the /dev/.udev directory are private to udev and do change whenever needed. +the /run/udev directory are private to udev and do change whenever needed. Requirements: - - Version 2.6.27 of the Linux kernel with sysfs, procfs, signalfd, inotify, - unix domain sockets, networking and hotplug enabled: + - Version 2.6.34 of the Linux kernel with sysfs, procfs, signalfd, inotify, + unix domain sockets, networking and hotplug enabled + + - Some architectures might need a later kernel, that supports accept4(), + or need to backport the accept4() syscall wiring in the kernel. + + - These options are needed: CONFIG_HOTPLUG=y CONFIG_UEVENT_HELPER_PATH="" CONFIG_NET=y @@ -25,13 +30,15 @@ Requirements: CONFIG_SYSFS=y CONFIG_SYSFS_DEPRECATED*=n CONFIG_PROC_FS=y - CONFIG_TMPFS=y CONFIG_INOTIFY_USER=y CONFIG_SIGNALFD=y + + - These options might be needed: + CONFIG_TMPFS=y CONFIG_TMPFS_POSIX_ACL=y (user ACLs for device nodes) CONFIG_BLK_DEV_BSG=y (SCSI devices) - - Udev will not work with the CONFIG_SYSFS_DEPRECATED* option. + - Udev does not work with the CONFIG_SYSFS_DEPRECATED* option. - Unix domain sockets (CONFIG_UNIX) as a loadable kernel module may work, but it is not supported. @@ -41,47 +48,47 @@ Requirements: unusable because the kernel may create too many processes in parallel so that the system runs out-of-memory. - - The proc filesystem must be mounted on /proc, the sysfs filesystem must + - The proc filesystem must be mounted on /proc, and the sysfs filesystem must be mounted at /sys. No other locations are supported by a standard udev installation. - - 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 + - The default rule sset requires the following group names resolvable at udev startup: + disk, cdrom, floppy, tape, audio, video, lp, tty, dialout, and kmem. + Especially in LDAP setups, it is required that getgrnam() be 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 configure option. + - Some udev extras have external dependencies like: + libacl, libglib2, usbutils, pciutils, and gperf. + All these extras can be disabled with configure options. Setup: - At bootup, the /dev directory should get the 'devtmpfs' filesystem - mounted. Udev will manage permissions and ownership of the kernel-created - device nodes, and possibly create additional symlinks. If needed, udev also - works on an empty 'tmpfs' filesystem, but some static device nodes like - /dev/null, /dev/console, /dev/kmsg are needed to be able to start udev itself. + mounted. Udev manages the permissions and ownership of the kernel-created + device nodes, and udev possibly creates additional symlinks. If needed, udev also + works on an empty 'tmpfs' filesystem, but some device nodes like + /dev/null, /dev/console, /dev/kmsg should be created before udevd is started. - The udev daemon should be started to handle device events sent by the kernel. - During bootup, the kernel can be asked to send events for all already existing - devices, to apply the configuration to these devices. This is usually done by: - /sbin/udevadm trigger --type=subsystems - /sbin/udevadm trigger --type=devices + During bootup, the events for already existing devices can be replayed, so + that they are configured by udev. This is usually done by: + /sbin/udevadm trigger --action=add --type=subsystems + /sbin/udevadm trigger --action=add --type=devices - - Restarting the daemon does never apply any rules to existing devices. + - Restarting the daemon never applies any rules to existing devices. - New/changed rule files are picked up automatically; there is no daemon restart or signal needed. Operation: - - Udev creates/removes device nodes in /dev, based on events the kernel - sends out on device creation/removal. + - Based on events the kernel sends out on device creation/removal, udev + creates/removes device nodes and symlinks in the /dev directory. - All kernel events are matched against a set of specified rules, which possibly hook into the event processing and load required kernel - modules to setup devices. For all devices the kernel exports a major/minor - number; if needed, udev will create a device node with the default kernel - name. If specified, udev applies permissions/ownership to the device + modules to set up devices. For all devices, the kernel exports a major/minor + number; if needed, udev creates a device node with the default kernel + device name. If specified, udev applies permissions/ownership to the device node, creates additional symlinks pointing to the node, and executes programs to handle the device. @@ -90,7 +97,8 @@ Operation: http://www.kernel.org/pub/linux/utils/kernel/hotplug/libudev/ http://www.kernel.org/pub/linux/utils/kernel/hotplug/gudev/ -For more details about udev and udev rules see the udev(7) man page. +For more details about udev and udev rules, see the udev man pages: + http://www.kernel.org/pub/linux/utils/kernel/hotplug/udev/ Please direct any comment/question to the linux-hotplug mailing list at: linux-hotplug@vger.kernel.org