X-Git-Url: http://www.chiark.greenend.org.uk/ucgi/~ianmdlvl/git?p=elogind.git;a=blobdiff_plain;f=README;h=5222637c2c77c210010e36df42fdd701e1a10fa7;hp=0d25b84fad9f2c604ad83271c51572e49b6c7eb2;hb=80cf9fb2e6f8117f408850cda5c1a8a932226766;hpb=12a362be5c1982f80dbfb75bda070208a2c99cdf diff --git a/README b/README index 0d25b84fa..5222637c2 100644 --- a/README +++ b/README @@ -1,104 +1,254 @@ -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 2.6.32. - -Tools and rules shipped by udev are not public API and may change at any time. -Never call any private tool in /usr/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 /usr/lib/udev and the entire contents -of the /run/udev directory are private to udev and do change whenever needed. - -Requirements: - - 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 - CONFIG_UNIX=y - CONFIG_SYSFS=y - CONFIG_SYSFS_DEPRECATED*=n - CONFIG_PROC_FS=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 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 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. - - - 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 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 events for already existing devices can be replayed, so - that they are configured by udev. This is usually done by: - udevadm trigger --action=add --type=subsystems - udevadm trigger --action=add --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 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 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. - - - 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 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 +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 src/shared/MurmurHash2.c which is Public Domain + - except src/shared/siphash24.c which is CC0 Public Domain + - except src/journal/lookup3.c which is Public Domain + - except src/udev/* which is (currently still) GPLv2, GPLv2+ + +REQUIREMENTS: + Linux kernel >= 3.7 + Linux kernel >= 3.8 for Smack support + + Kernel Config Options: + CONFIG_DEVTMPFS + CONFIG_CGROUPS (it is OK to disable all controllers) + CONFIG_INOTIFY_USER + CONFIG_SIGNALFD + CONFIG_TIMERFD + CONFIG_EPOLL + CONFIG_NET + CONFIG_SYSFS + CONFIG_PROC_FS + CONFIG_FHANDLE (libudev, mount and bind mount handling) + + udev will fail to work with the legacy sysfs layout: + CONFIG_SYSFS_DEPRECATED=n + + Legacy hotplug slows down the system and confuses udev: + CONFIG_UEVENT_HELPER_PATH="" + + Userspace firmware loading is not supported and should + be disabled in the kernel: + CONFIG_FW_LOADER_USER_HELPER=n + + Some udev rules and virtualization detection relies on it: + CONFIG_DMIID + + Support for some SCSI devices serial number retrieval, to + create additional symlinks in /dev/disk/ and /dev/tape: + CONFIG_BLK_DEV_BSG + + Required for PrivateNetwork and PrivateDevices in service units: + CONFIG_NET_NS + CONFIG_DEVPTS_MULTIPLE_INSTANCES + Note that systemd-localed.service and other systemd units use + PrivateNetwork and PrivateDevices so this is effectively required. + + Optional but strongly recommended: + CONFIG_IPV6 + CONFIG_AUTOFS4_FS + CONFIG_TMPFS_XATTR + CONFIG_{TMPFS,EXT4,XFS,BTRFS_FS,...}_POSIX_ACL + CONFIG_SECCOMP + + Required for CPUShares in resource control unit settings + CONFIG_CGROUP_SCHED + CONFIG_FAIR_GROUP_SCHED + + Required for CPUQuota in resource control unit settings + CONFIG_CFS_BANDWIDTH + + For systemd-bootchart, several proc debug interfaces are required: + CONFIG_SCHEDSTATS + CONFIG_SCHED_DEBUG + + For UEFI systems: + CONFIG_EFIVAR_FS + 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 + If systemd is compiled with libseccomp support on + architectures which do not use socketcall() and where seccomp + is supported (this effectively means x86-64 and ARM, but + excludes 32-bit x86!), then nspawn will now install a + work-around seccomp filter that makes containers boot even + with audit being enabled. This works correctly only on kernels + 3.14 and newer though. TL;DR: turn audit off, still. + + glibc >= 2.14 + libcap + libmount >= 2.20 (from util-linux) + libseccomp >= 1.0.0 (optional) + libblkid >= 2.24 (from util-linux) (optional) + libkmod >= 15 (optional) + PAM >= 1.1.2 (optional) + libcryptsetup (optional) + libaudit (optional) + libacl (optional) + libselinux (optional) + liblzma (optional) + liblz4 >= 119 (optional) + libgcrypt (optional) + libqrencode (optional) + libmicrohttpd (optional) + libpython (optional) + libidn (optional) + gobject-introspection > 1.40.0 (optional) + elfutils >= 158 (optional) + make, gcc, and similar tools + + During runtime, you need the following additional + dependencies: + + util-linux >= v2.25 required + dbus >= 1.4.0 (strictly speaking optional, but recommended) + dracut (optional) + PolicyKit (optional) + + When building from git, you need the following additional + dependencies: + + pkg-config + docbook-xsl + xsltproc + automake + autoconf + libtool + intltool + gperf + gtkdocize (optional) + python (optional) + python-lxml (optional, but required to build the indices) + sphinx (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-', with + 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: + + audio, cdrom, dialout, disk, input, kmem, lp, tape, tty, video + + 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. In addition, system + groups "wheel" and "adm" will be given read-only access to + journal files using systemd-tmpfiles.service. + + 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. + + Similarly, the NTP daemon requires the "systemd-timesync" system + user and group to exist. + + Similarly, the network management daemon requires the + "systemd-network" system user and group to exist. + + Similarly, the name resolution daemon requires the + "systemd-resolve" system user and group to exist. + + Similarly, the kdbus dbus1 proxy daemon requires the + "systemd-bus-proxy" system user and group to exist. + +NSS: + systemd ships with three NSS modules: + + nss-myhostname resolves the local hostname to locally + configured IP addresses, as well as "localhost" to + 127.0.0.1/::1. + + nss-resolve enables DNS resolution via the systemd-resolved + DNS/LLMNR caching stub resolver "systemd-resolved". + + nss-mymachines enables resolution of all local containers + registered with machined to their respective IP addresses. + + To make use of these NSS modules, please add them to the + "hosts: " line in /etc/nsswitch.conf. The "resolve" module + should replace the glibc "dns" module in this file. + + The three modules should be used in the following order: + + hosts: files mymachines resolve myhostname + +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. + + systemd requires that the /run mount point exists. systemd also + requires that /var/run is a a symlink to /run. + + 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. + +ENGINEERING AND CONSULTING SERVICES: + ENDOCODE offers professional + engineering and consulting services for systemd. Please + contact Chris Kühl for more information.