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