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
 184 USERS AND GROUPS:
 185         Default udev rules use the following standard system group
 186         names, which need to be resolvable by getgrnam() at any time,
 187         even in the very early boot stages, where no other databases
 188         and network are available:
 189
 190         audio, cdrom, dialout, disk, input, kmem, lp, tape, tty, video
 191
 192         During runtime, the journal daemon requires the
 193         "systemd-journal" system group to exist. New journal files will
 194         be readable by this group (but not writable), which may be used
 195         to grant specific users read access. In addition, system
 196         groups "wheel" and "adm" will be given read-only access to
 197         journal files using systemd-tmpfiles.service.
 198
 199         The journal gateway daemon requires the
 200         "systemd-journal-gateway" system user and group to
 201         exist. During execution this network facing service will drop
 202         privileges and assume this uid/gid for security reasons.
 203
 204         Similarly, the NTP daemon requires the "systemd-timesync" system
 205         user and group to exist.
 206
 207         Similarly, the network management daemon requires the
 208         "systemd-network" system user and group to exist.
 209
 210         Similarly, the name resolution daemon requires the
 211         "systemd-resolve" system user and group to exist.
 212
 213         Similarly, the coredump support requires the
 214         "systemd-coredump" system user and group to exist.
 215
 216 NSS:
 217         systemd ships with four glibc NSS modules:
 218
 219         nss-myhostname resolves the local hostname to locally
 220         configured IP addresses, as well as "localhost" to
 221         127.0.0.1/::1.
 222
 223         nss-resolve enables DNS resolution via the systemd-resolved
 224         DNS/LLMNR caching stub resolver "systemd-resolved".
 225
 226         nss-mymachines enables resolution of all local containers registered
 227         with machined to their respective IP addresses. It also maps UID/GIDs
 228         ranges used by containers to useful names.
 229
 230         nss-systemd enables resolution of all dynamically allocated service
 231         users. (See the DynamicUser= setting in unit files.)
 232
 233         To make use of these NSS modules, please add them to the "hosts:",
 234         "passwd:" and "group:" lines in /etc/nsswitch.conf. The "resolve"
 235         module should replace the glibc "dns" module in this file (and don't
 236         worry, it chain-loads the "dns" module if it can't talk to resolved).
 237
 238         The four modules should be used in the following order:
 239
 240                 passwd: compat mymachines systemd
 241                 group: compat mymachines systemd
 242                 hosts: files mymachines resolve myhostname
 243
 244 SYSV INIT.D SCRIPTS:
 245         When calling "systemctl enable/disable/is-enabled" on a unit which is a
 246         SysV init.d script, it calls /usr/lib/systemd/systemd-sysv-install;
 247         this needs to translate the action into the distribution specific
 248         mechanism such as chkconfig or update-rc.d. Packagers need to provide
 249         this script if you need this functionality (you don't if you disabled
 250         SysV init support).
 251
 252         Please see src/systemctl/systemd-sysv-install.SKELETON for how this
 253         needs to look like, and provide an implementation at the marked places.
 254
 255 WARNINGS:
 256         systemd will warn you during boot if /usr is on a different
 257         file system than /. While in systemd itself very little will
 258         break if /usr is on a separate partition, many of its
 259         dependencies very likely will break sooner or later in one
 260         form or another. For example, udev rules tend to refer to
 261         binaries in /usr, binaries that link to libraries in /usr or
 262         binaries that refer to data files in /usr. Since these
 263         breakages are not always directly visible, systemd will warn
 264         about this, since this kind of file system setup is not really
 265         supported anymore by the basic set of Linux OS components.
 266
 267         systemd requires that the /run mount point exists. systemd also
 268         requires that /var/run is a symlink to /run.
 269
 270         For more information on this issue consult
 271         http://freedesktop.org/wiki/Software/systemd/separate-usr-is-broken
 272
 273         To run systemd under valgrind, compile with VALGRIND defined
 274         (e.g. ./configure CPPFLAGS='... -DVALGRIND=1'). Otherwise,
 275         false positives will be triggered by code which violates
 276         some rules but is actually safe.
 277
 278         Currently, systemd-timesyncd defaults to use the Google NTP
 279         servers if not specified otherwise at configure time. You
 280         really should not ship an OS or device with this default
 281         setting. See DISTRO_PORTING for details.
 282
 283 ENGINEERING AND CONSULTING SERVICES:
 284         Kinvolk (https://kinvolk.io) offers professional engineering
 285         and consulting services for systemd. Please contact Chris Kühl
 286         <chris@kinvolk.io> for more information.