README

   1 systemd System and Service Manager
   2
   3 DETAILS:
   4         http://0pointer.de/blog/projects/systemd.html
   5
   6 WEB SITE:
   7         http://www.freedesktop.org/wiki/Software/systemd
   8
   9 GIT:
  10         git@github.com:systemd/systemd.git
  11         https://github.com/systemd/systemd.git
  12
  13 GITWEB:
  14         https://github.com/systemd/systemd
  15
  16 MAILING LIST:
  17         http://lists.freedesktop.org/mailman/listinfo/systemd-devel
  18
  19 IRC:
  20         #systemd on irc.freenode.org
  21
  22 BUG REPORTS:
  23         https://github.com/systemd/systemd/issues
  24
  25 AUTHOR:
  26         Lennart Poettering
  27         Kay Sievers
  28         ...and many others
  29
  30 LICENSE:
  31         LGPLv2.1+ for all code
  32         - except src/basic/MurmurHash2.c which is Public Domain
  33         - except src/basic/siphash24.c which is CC0 Public Domain
  34         - except src/journal/lookup3.c which is Public Domain
  35         - except src/udev/* which is (currently still) GPLv2, GPLv2+
  36
  37 REQUIREMENTS:
  38         Linux kernel >= 3.12
  39         Linux kernel >= 4.2 for unified cgroup hierarchy support
  40
  41         Kernel Config Options:
  42           CONFIG_DEVTMPFS
  43           CONFIG_CGROUPS (it is OK to disable all controllers)
  44           CONFIG_INOTIFY_USER
  45           CONFIG_SIGNALFD
  46           CONFIG_TIMERFD
  47           CONFIG_EPOLL
  48           CONFIG_NET
  49           CONFIG_SYSFS
  50           CONFIG_PROC_FS
  51           CONFIG_FHANDLE (libudev, mount and bind mount handling)
  52
  53         udev will fail to work with the legacy sysfs layout:
  54           CONFIG_SYSFS_DEPRECATED=n
  55
  56         Legacy hotplug slows down the system and confuses udev:
  57           CONFIG_UEVENT_HELPER_PATH=""
  58
  59         Userspace firmware loading is not supported and should
  60         be disabled in the kernel:
  61           CONFIG_FW_LOADER_USER_HELPER=n
  62
  63         Some udev rules and virtualization detection relies on it:
  64           CONFIG_DMIID
  65
  66         Support for some SCSI devices serial number retrieval, to
  67         create additional symlinks in /dev/disk/ and /dev/tape:
  68           CONFIG_BLK_DEV_BSG
  69
  70         Required for PrivateNetwork= and PrivateDevices= in service units:
  71           CONFIG_NET_NS
  72           CONFIG_DEVPTS_MULTIPLE_INSTANCES
  73         Note that systemd-localed.service and other systemd units use
  74         PrivateNetwork and PrivateDevices so this is effectively required.
  75
  76         Required for PrivateUsers= in service units:
  77           CONFIG_USER_NS
  78
  79         Optional but strongly recommended:
  80           CONFIG_IPV6
  81           CONFIG_AUTOFS4_FS
  82           CONFIG_TMPFS_XATTR
  83           CONFIG_{TMPFS,EXT4,XFS,BTRFS_FS,...}_POSIX_ACL
  84           CONFIG_SECCOMP
  85           CONFIG_SECCOMP_FILTER (required for seccomp support)
  86           CONFIG_CHECKPOINT_RESTORE (for the kcmp() syscall)
  87
  88         Required for CPUShares= in resource control unit settings
  89           CONFIG_CGROUP_SCHED
  90           CONFIG_FAIR_GROUP_SCHED
  91
  92         Required for CPUQuota= in resource control unit settings
  93           CONFIG_CFS_BANDWIDTH
  94
  95         For UEFI systems:
  96           CONFIG_EFIVAR_FS
  97           CONFIG_EFI_PARTITION
  98
  99         We recommend to turn off Real-Time group scheduling in the
 100         kernel when using systemd. RT group scheduling effectively
 101         makes RT scheduling unavailable for most userspace, since it
 102         requires explicit assignment of RT budgets to each unit whose
 103         processes making use of RT. As there's no sensible way to
 104         assign these budgets automatically this cannot really be
 105         fixed, and it's best to disable group scheduling hence.
 106            CONFIG_RT_GROUP_SCHED=n
 107
 108         Note that kernel auditing is broken when used with systemd's
 109         container code. When using systemd in conjunction with
 110         containers, please make sure to either turn off auditing at
 111         runtime using the kernel command line option "audit=0", or
 112         turn it off at kernel compile time using:
 113           CONFIG_AUDIT=n
 114         If systemd is compiled with libseccomp support on
 115         architectures which do not use socketcall() and where seccomp
 116         is supported (this effectively means x86-64 and ARM, but
 117         excludes 32-bit x86!), then nspawn will now install a
 118         work-around seccomp filter that makes containers boot even
 119         with audit being enabled. This works correctly only on kernels
 120         3.14 and newer though. TL;DR: turn audit off, still.
 121
 122         glibc >= 2.16
 123         libcap
 124         libmount >= 2.27.1 (from util-linux)
 125                 (util-linux *must* be built with --enable-libmount-force-mountinfo)
 126         libseccomp >= 2.3.1 (optional)
 127         libblkid >= 2.24 (from util-linux) (optional)
 128         libkmod >= 15 (optional)
 129         PAM >= 1.1.2 (optional)
 130         libcryptsetup (optional)
 131         libaudit (optional)
 132         libacl (optional)
 133         libselinux (optional)
 134         liblzma (optional)
 135         liblz4 >= 119 (optional)
 136         libgcrypt (optional)
 137         libqrencode (optional)
 138         libmicrohttpd (optional)
 139         libpython (optional)
 140         libidn (optional)
 141         elfutils >= 158 (optional)
 142         make, gcc, and similar tools
 143
 144         During runtime, you need the following additional
 145         dependencies:
 146
 147         util-linux >= v2.27.1 required
 148         dbus >= 1.4.0 (strictly speaking optional, but recommended)
 149                 NOTE: If using dbus < 1.9.18, you should override the default
 150                 policy directory (--with-dbuspolicydir=/etc/dbus-1/system.d).
 151         dracut (optional)
 152         PolicyKit (optional)
 153
 154         When building from git, the following tools are needed:
 155
 156         pkg-config
 157         docbook-xsl
 158         xsltproc
 159         automake
 160         autoconf
 161         libtool
 162         intltool
 163         gperf
 164         python (optional)
 165         python-lxml (optional, but required to build the indices)
 166
 167         The build system is initialized with ./autogen.sh. A tar ball
 168         can be created with:
 169           git archive --format=tar --prefix=systemd-222/ v222 | xz > systemd-222.tar.xz
 170
 171         When systemd-hostnamed is used, it is strongly recommended to
 172         install nss-myhostname to ensure that, in a world of
 173         dynamically changing hostnames, the hostname stays resolvable
 174         under all circumstances. In fact, systemd-hostnamed will warn
 175         if nss-myhostname is not installed.
 176
 177         Additional packages are necessary to run some tests:
 178         - busybox            (used by test/TEST-13-NSPAWN-SMOKE)
 179         - nc                 (used by test/TEST-12-ISSUE-3171)
 180         - python3-pyparsing
 181         - python3-evdev      (used by hwdb parsing tests)
 182         - strace             (used by test/test-functions)
 183         - capsh              (optional, used by test-execute)
 184
 185 USERS AND GROUPS:
 186         Default udev rules use the following standard system group
 187         names, which need to be resolvable by getgrnam() at any time,
 188         even in the very early boot stages, where no other databases
 189         and network are available:
 190
 191         audio, cdrom, dialout, disk, input, kmem, lp, tape, tty, video
 192
 193         During runtime, the journal daemon requires the
 194         "systemd-journal" system group to exist. New journal files will
 195         be readable by this group (but not writable), which may be used
 196         to grant specific users read access. In addition, system
 197         groups "wheel" and "adm" will be given read-only access to
 198         journal files using systemd-tmpfiles.service.
 199
 200         The journal gateway daemon requires the
 201         "systemd-journal-gateway" system user and group to
 202         exist. During execution this network facing service will drop
 203         privileges and assume this uid/gid for security reasons.
 204
 205         Similarly, the NTP daemon requires the "systemd-timesync" system
 206         user and group to exist.
 207
 208         Similarly, the network management daemon requires the
 209         "systemd-network" system user and group to exist.
 210
 211         Similarly, the name resolution daemon requires the
 212         "systemd-resolve" system user and group to exist.
 213
 214         Similarly, the coredump support requires the
 215         "systemd-coredump" system user and group to exist.
 216
 217 NSS:
 218         systemd ships with four glibc NSS modules:
 219
 220         nss-myhostname resolves the local hostname to locally
 221         configured IP addresses, as well as "localhost" to
 222         127.0.0.1/::1.
 223
 224         nss-resolve enables DNS resolution via the systemd-resolved
 225         DNS/LLMNR caching stub resolver "systemd-resolved".
 226
 227         nss-mymachines enables resolution of all local containers registered
 228         with machined to their respective IP addresses. It also maps UID/GIDs
 229         ranges used by containers to useful names.
 230
 231         nss-systemd enables resolution of all dynamically allocated service
 232         users. (See the DynamicUser= setting in unit files.)
 233
 234         To make use of these NSS modules, please add them to the "hosts:",
 235         "passwd:" and "group:" lines in /etc/nsswitch.conf. The "resolve"
 236         module should replace the glibc "dns" module in this file (and don't
 237         worry, it chain-loads the "dns" module if it can't talk to resolved).
 238
 239         The four modules should be used in the following order:
 240
 241                 passwd: compat mymachines systemd
 242                 group: compat mymachines systemd
 243                 hosts: files mymachines resolve myhostname
 244
 245 SYSV INIT.D SCRIPTS:
 246         When calling "systemctl enable/disable/is-enabled" on a unit which is a
 247         SysV init.d script, it calls /usr/lib/systemd/systemd-sysv-install;
 248         this needs to translate the action into the distribution specific
 249         mechanism such as chkconfig or update-rc.d. Packagers need to provide
 250         this script if you need this functionality (you don't if you disabled
 251         SysV init support).
 252
 253         Please see src/systemctl/systemd-sysv-install.SKELETON for how this
 254         needs to look like, and provide an implementation at the marked places.
 255
 256 WARNINGS:
 257         systemd will warn you during boot if /usr is on a different
 258         file system than /. While in systemd itself very little will
 259         break if /usr is on a separate partition, many of its
 260         dependencies very likely will break sooner or later in one
 261         form or another. For example, udev rules tend to refer to
 262         binaries in /usr, binaries that link to libraries in /usr or
 263         binaries that refer to data files in /usr. Since these
 264         breakages are not always directly visible, systemd will warn
 265         about this, since this kind of file system setup is not really
 266         supported anymore by the basic set of Linux OS components.
 267
 268         systemd requires that the /run mount point exists. systemd also
 269         requires that /var/run is a symlink to /run.
 270
 271         For more information on this issue consult
 272         http://freedesktop.org/wiki/Software/systemd/separate-usr-is-broken
 273
 274         To run systemd under valgrind, compile with VALGRIND defined
 275         (e.g. ./configure CPPFLAGS='... -DVALGRIND=1'). Otherwise,
 276         false positives will be triggered by code which violates
 277         some rules but is actually safe.
 278
 279 ENGINEERING AND CONSULTING SERVICES:
 280         Kinvolk (https://kinvolk.io) offers professional engineering
 281         and consulting services for systemd. Please contact Chris Kühl
 282         <chris@kinvolk.io> for more information.