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         Optional but strongly recommended:
  77           CONFIG_IPV6
  78           CONFIG_AUTOFS4_FS
  79           CONFIG_TMPFS_XATTR
  80           CONFIG_{TMPFS,EXT4,XFS,BTRFS_FS,...}_POSIX_ACL
  81           CONFIG_SECCOMP
  82           CONFIG_SECCOMP_FILTER (required for seccomp support)
  83           CONFIG_CHECKPOINT_RESTORE (for the kcmp() syscall)
  84
  85         Required for CPUShares= in resource control unit settings
  86           CONFIG_CGROUP_SCHED
  87           CONFIG_FAIR_GROUP_SCHED
  88
  89         Required for CPUQuota= in resource control unit settings
  90           CONFIG_CFS_BANDWIDTH
  91
  92         For UEFI systems:
  93           CONFIG_EFIVAR_FS
  94           CONFIG_EFI_PARTITION
  95
  96         We recommend to turn off Real-Time group scheduling in the
  97         kernel when using systemd. RT group scheduling effectively
  98         makes RT scheduling unavailable for most userspace, since it
  99         requires explicit assignment of RT budgets to each unit whose
 100         processes making use of RT. As there's no sensible way to
 101         assign these budgets automatically this cannot really be
 102         fixed, and it's best to disable group scheduling hence.
 103            CONFIG_RT_GROUP_SCHED=n
 104
 105         Note that kernel auditing is broken when used with systemd's
 106         container code. When using systemd in conjunction with
 107         containers, please make sure to either turn off auditing at
 108         runtime using the kernel command line option "audit=0", or
 109         turn it off at kernel compile time using:
 110           CONFIG_AUDIT=n
 111         If systemd is compiled with libseccomp support on
 112         architectures which do not use socketcall() and where seccomp
 113         is supported (this effectively means x86-64 and ARM, but
 114         excludes 32-bit x86!), then nspawn will now install a
 115         work-around seccomp filter that makes containers boot even
 116         with audit being enabled. This works correctly only on kernels
 117         3.14 and newer though. TL;DR: turn audit off, still.
 118
 119         glibc >= 2.16
 120         libcap
 121         libmount >= 2.27.1 (from util-linux)
 122                 (util-linux *must* be built with --enable-libmount-force-mountinfo)
 123         libseccomp >= 1.0.0 (optional)
 124         libblkid >= 2.24 (from util-linux) (optional)
 125         libkmod >= 15 (optional)
 126         PAM >= 1.1.2 (optional)
 127         libcryptsetup (optional)
 128         libaudit (optional)
 129         libacl (optional)
 130         libselinux (optional)
 131         liblzma (optional)
 132         liblz4 >= 119 (optional)
 133         libgcrypt (optional)
 134         libqrencode (optional)
 135         libmicrohttpd (optional)
 136         libpython (optional)
 137         libidn (optional)
 138         elfutils >= 158 (optional)
 139         make, gcc, and similar tools
 140
 141         During runtime, you need the following additional
 142         dependencies:
 143
 144         util-linux >= v2.27.1 required
 145         dbus >= 1.4.0 (strictly speaking optional, but recommended)
 146         dracut (optional)
 147         PolicyKit (optional)
 148
 149         When building from git, the following tools are needed:
 150
 151         pkg-config
 152         docbook-xsl
 153         xsltproc
 154         automake
 155         autoconf
 156         libtool
 157         intltool
 158         gperf
 159         python (optional)
 160         python-lxml (optional, but required to build the indices)
 161
 162         The build system is initialized with ./autogen.sh. A tar ball
 163         can be created with:
 164           git archive --format=tar --prefix=systemd-222/ v222 | xz > systemd-222.tar.xz
 165
 166         When systemd-hostnamed is used, it is strongly recommended to
 167         install nss-myhostname to ensure that, in a world of
 168         dynamically changing hostnames, the hostname stays resolvable
 169         under all circumstances. In fact, systemd-hostnamed will warn
 170         if nss-myhostname is not installed.
 171
 172 USERS AND GROUPS:
 173         Default udev rules use the following standard system group
 174         names, which need to be resolvable by getgrnam() at any time,
 175         even in the very early boot stages, where no other databases
 176         and network are available:
 177
 178         audio, cdrom, dialout, disk, input, kmem, lp, tape, tty, video
 179
 180         During runtime, the journal daemon requires the
 181         "systemd-journal" system group to exist. New journal files will
 182         be readable by this group (but not writable), which may be used
 183         to grant specific users read access. In addition, system
 184         groups "wheel" and "adm" will be given read-only access to
 185         journal files using systemd-tmpfiles.service.
 186
 187         The journal gateway daemon requires the
 188         "systemd-journal-gateway" system user and group to
 189         exist. During execution this network facing service will drop
 190         privileges and assume this uid/gid for security reasons.
 191
 192         Similarly, the NTP daemon requires the "systemd-timesync" system
 193         user and group to exist.
 194
 195         Similarly, the network management daemon requires the
 196         "systemd-network" system user and group to exist.
 197
 198         Similarly, the name resolution daemon requires the
 199         "systemd-resolve" system user and group to exist.
 200
 201         Similarly, the coredump support requires the
 202         "systemd-coredump" system user and group to exist.
 203
 204 NSS:
 205         systemd ships with four glibc NSS modules:
 206
 207         nss-myhostname resolves the local hostname to locally
 208         configured IP addresses, as well as "localhost" to
 209         127.0.0.1/::1.
 210
 211         nss-resolve enables DNS resolution via the systemd-resolved
 212         DNS/LLMNR caching stub resolver "systemd-resolved".
 213
 214         nss-mymachines enables resolution of all local containers registered
 215         with machined to their respective IP addresses. It also maps UID/GIDs
 216         ranges used by containers to useful names.
 217
 218         nss-systemd enables resolution of all dynamically allocated service
 219         users. (See the DynamicUser= setting in unit files.)
 220
 221         To make use of these NSS modules, please add them to the "hosts:",
 222         "passwd:" and "group:" lines in /etc/nsswitch.conf. The "resolve"
 223         module should replace the glibc "dns" module in this file (and don't
 224         worry, it chain-loads the "dns" module if it can't talk to resolved).
 225
 226         The four modules should be used in the following order:
 227
 228                 passwd: compat mymachines systemd
 229                 group: compat mymachines systemd
 230                 hosts: files mymachines resolve myhostname
 231
 232 SYSV INIT.D SCRIPTS:
 233         When calling "systemctl enable/disable/is-enabled" on a unit which is a
 234         SysV init.d script, it calls /usr/lib/systemd/systemd-sysv-install;
 235         this needs to translate the action into the distribution specific
 236         mechanism such as chkconfig or update-rc.d. Packagers need to provide
 237         this script if you need this functionality (you don't if you disabled
 238         SysV init support).
 239
 240         Please see src/systemctl/systemd-sysv-install.SKELETON for how this
 241         needs to look like, and provide an implementation at the marked places.
 242
 243 WARNINGS:
 244         systemd will warn you during boot if /usr is on a different
 245         file system than /. While in systemd itself very little will
 246         break if /usr is on a separate partition, many of its
 247         dependencies very likely will break sooner or later in one
 248         form or another. For example, udev rules tend to refer to
 249         binaries in /usr, binaries that link to libraries in /usr or
 250         binaries that refer to data files in /usr. Since these
 251         breakages are not always directly visible, systemd will warn
 252         about this, since this kind of file system setup is not really
 253         supported anymore by the basic set of Linux OS components.
 254
 255         systemd requires that the /run mount point exists. systemd also
 256         requires that /var/run is a symlink to /run.
 257
 258         For more information on this issue consult
 259         http://freedesktop.org/wiki/Software/systemd/separate-usr-is-broken
 260
 261         To run systemd under valgrind, compile with VALGRIND defined
 262         (e.g. ./configure CPPFLAGS='... -DVALGRIND=1'). Otherwise,
 263         false positives will be triggered by code which violates
 264         some rules but is actually safe.
 265
 266         Currently, systemd-timesyncd defaults to use the Google NTP
 267         servers if not specified otherwise at configure time. You
 268         really should not ship an OS or device with this default
 269         setting. See DISTRO_PORTING for details.
 270
 271 ENGINEERING AND CONSULTING SERVICES:
 272         Kinvolk (https://kinvolk.io) offers professional engineering
 273         and consulting services for systemd. Please contact Chris Kühl
 274         <chris@kinvolk.io> for more information.