-udev - Linux userspace device management
-
-Integrating udev in the system has complex dependencies and may differ from
-distribution to distribution. A system may not be able to boot up or work
-reliably without a properly installed udev version. The upstream udev project
-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.
-
-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.
-
-Requirements:
- - 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=""
- CONFIG_NET=y
- CONFIG_UNIX=y
- CONFIG_SYSFS=y
- CONFIG_SYSFS_DEPRECATED*=n
- CONFIG_PROC_FS=y
- CONFIG_TMPFS=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)
-
- - 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.
-
- - 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.
-
- - 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, 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.
-
- - The 'udev extras' has the following dependencies:
- libacl, libglib2, libusb, usbutils, pciutils, and gperf.
- These dependencies can be disabled with the --disable-extras configure option.
-
-Setup:
- - At bootup, the /dev directory should get the 'devtmpfs' filesystem
- 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 static device nodes like
- /dev/null, /dev/console, /dev/kmsg are needed to be able to start udev itself.
-
- - 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 so that they too can be configured by udev. This is usually done by:
- /sbin/udevadm trigger --type=subsystems
- /sbin/udevadm trigger --type=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:
- - Based on events the kernel sends out on device creation/removal, udev
- creates/removes device nodes 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 set up devices. For all devices, the kernel exports a major/minor
- number; if needed, udev creates a device node with the default kernel
- 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.
-
- - The events udev handles, and the information udev merges into its device
- database, can be accessed with libudev:
- 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.
-
-Please direct any comment/question to the linux-hotplug mailing list at:
- linux-hotplug@vger.kernel.org
+systemd System and Service Manager
+
+DETAILS:
+ http://0pointer.de/blog/projects/systemd.html
+
+WEB SITE:
+ http://www.freedesktop.org/wiki/Software/systemd
+
+GIT:
+ git://anongit.freedesktop.org/systemd/systemd
+ ssh://git.freedesktop.org/git/systemd/systemd
+
+GITWEB:
+ http://cgit.freedesktop.org/systemd/systemd
+
+MAILING LIST:
+ http://lists.freedesktop.org/mailman/listinfo/systemd-devel
+ http://lists.freedesktop.org/mailman/listinfo/systemd-commits
+
+IRC:
+ #systemd on irc.freenode.org
+
+BUG REPORTS:
+ https://bugs.freedesktop.org/enter_bug.cgi?product=systemd
+
+AUTHOR:
+ Lennart Poettering
+ Kay Sievers
+ ...and many others
+
+LICENSE:
+ LGPLv2.1+ for all code
+ - except sd-daemon.[ch] and sd-readahead.[ch] which are MIT
+ - except src/shared/MurmurHash3.c which is Public Domain
+ - except src/journal/lookup3.c which is Public Domain
+ - except src/udev/* which is (currently still) GPLv2, GPLv2+
+
+REQUIREMENTS:
+ Linux kernel >= 3.0
+ CONFIG_DEVTMPFS
+ CONFIG_CGROUPS (it's OK to disable all controllers)
+ CONFIG_INOTIFY_USER
+ CONFIG_SIGNALFD
+ CONFIG_TIMERFD
+ CONFIG_EPOLL
+ CONFIG_NET
+ CONFIG_SYSFS
+ CONFIG_PROC_FS
+
+ Linux kernel >= 3.8 for Smack support
+
+ Udev will fail to work with the legacy layout:
+ CONFIG_SYSFS_DEPRECATED=n
+
+ Legacy hotplug slows down the system and confuses udev:
+ CONFIG_UEVENT_HELPER_PATH=""
+
+ Userspace firmware loading is deprecated, will go away, and
+ sometimes causes problems:
+ CONFIG_FW_LOADER_USER_HELPER=n
+
+ Some udev rules and virtualization detection relies on it:
+ CONFIG_DMIID
+
+ Mount and bind mount handling might require it:
+ CONFIG_FHANDLE
+
+ Support for some SCSI devices serial number retrieval, to
+ create additional symlinks in /dev/disk/ and /dev/tape:
+ CONFIG_BLK_DEV_BSG
+
+ Optional but strongly recommended:
+ CONFIG_IPV6
+ CONFIG_AUTOFS4_FS
+ CONFIG_TMPFS_POSIX_ACL
+ CONFIG_TMPFS_XATTR
+ CONFIG_SECCOMP
+
+ For systemd-bootchart, several proc debug interfaces are required:
+ CONFIG_SCHEDSTATS
+ CONFIG_SCHED_DEBUG
+
+ For UEFI systems:
+ CONFIG_EFI_VARS
+ CONFIG_EFI_PARTITION
+
+ Note that kernel auditing is broken when used with systemd's
+ container code. When using systemd in conjunction with
+ containers, please make sure to either turn off auditing at
+ runtime using the kernel command line option "audit=0", or
+ turn it off at kernel compile time using:
+ CONFIG_AUDIT=n
+
+ glibc >= 2.14
+ libcap
+ libblkid >= 2.20 (from util-linux) (optional)
+ libkmod >= 15 (optional)
+ PAM >= 1.1.2 (optional)
+ libcryptsetup (optional)
+ libaudit (optional)
+ libacl (optional)
+ libattr (optional)
+ libselinux (optional)
+ liblzma (optional)
+ tcpwrappers (optional)
+ libgcrypt (optional)
+ libqrencode (optional)
+ libmicrohttpd (optional)
+ libpython (optional)
+ make, gcc, and similar tools
+
+ During runtime, you need the following additional
+ dependencies:
+
+ util-linux >= v2.19 (requires fsck -l, agetty -s),
+ v2.21 required for tests in test/
+ dbus >= 1.4.0 (strictly speaking optional, but recommended)
+ sulogin (from util-linux >= 2.22 or sysvinit-tools, optional but recommended,
+ required for tests in test/)
+ dracut (optional)
+ PolicyKit (optional)
+
+ When building from git, you need the following additional
+ dependencies:
+
+ docbook-xsl
+ xsltproc
+ automake
+ autoconf
+ libtool
+ intltool
+ gperf
+ gtkdocize (optional)
+ python (optional)
+ sphinx (optional)
+ python-lxml (entirely optional)
+
+ When systemd-hostnamed is used, it is strongly recommended to
+ install nss-myhostname to ensure that, in a world of
+ dynamically changing hostnames, the hostname stays resolvable
+ under all circumstances. In fact, systemd-hostnamed will warn
+ if nss-myhostname is not installed.
+
+ To build HTML documentation for python-systemd using sphinx,
+ please first install systemd (using 'make install'), and then
+ invoke sphinx-build with 'make sphinx-<target>', with <target>
+ being 'html' or 'latexpdf'. If using DESTDIR for installation,
+ pass the same DESTDIR to 'make sphinx-html' invocation.
+
+USERS AND GROUPS:
+ Default udev rules use the following standard system group
+ names, which need to be resolvable by getgrnam() at any time,
+ even in the very early boot stages, where no other databases
+ and network are available:
+
+ tty, dialout, kmem, video, audio, lp, floppy, cdrom, tape, disk
+
+ During runtime, the journal daemon requires the
+ "systemd-journal" system group to exist. New journal files will
+ be readable by this group (but not writable), which may be used
+ to grant specific users read access.
+
+ It is also recommended to grant read access to all journal
+ files to the system groups "wheel" and "adm" with a command
+ like the following in the post installation script of the
+ package:
+
+ # setfacl -nm g:wheel:rx,d:g:wheel:rx,g:adm:rx,d:g:adm:rx /var/log/journal/
+
+ The journal gateway daemon requires the
+ "systemd-journal-gateway" system user and group to
+ exist. During execution this network facing service will drop
+ privileges and assume this uid/gid for security reasons.
+
+WARNINGS:
+ systemd will warn you during boot if /etc/mtab is not a
+ symlink to /proc/mounts. Please ensure that /etc/mtab is a
+ proper symlink.
+
+ systemd will warn you during boot if /usr is on a different
+ file system than /. While in systemd itself very little will
+ break if /usr is on a separate partition, many of its
+ dependencies very likely will break sooner or later in one
+ form or another. For example, udev rules tend to refer to
+ binaries in /usr, binaries that link to libraries in /usr or
+ binaries that refer to data files in /usr. Since these
+ breakages are not always directly visible, systemd will warn
+ about this, since this kind of file system setup is not really
+ supported anymore by the basic set of Linux OS components.
+
+ For more information on this issue consult
+ http://freedesktop.org/wiki/Software/systemd/separate-usr-is-broken
+
+ To run systemd under valgrind, compile with VALGRIND defined
+ (e.g. ./configure CPPFLAGS='... -DVALGRIND=1'). Otherwise,
+ false positives will be triggered by code which violates
+ some rules but is actually safe.
~ianmdlvl / elogind.git / blobdiff