README

   1 systemd System and Service Manager
   2
   3 DETAILS:
   4         http://0pointer.de/blog/projects/systemd.html
   5
   6 WEB SITE:
   7         https://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         https://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 >= 3.13
  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         Kernel crypto/hash API
  54           CONFIG_CRYPTO_USER_API_HASH
  55           CONFIG_CRYPTO_HMAC
  56           CONFIG_CRYPTO_SHA256
  57
  58         udev will fail to work with the legacy sysfs layout:
  59           CONFIG_SYSFS_DEPRECATED=n
  60
  61         Legacy hotplug slows down the system and confuses udev:
  62           CONFIG_UEVENT_HELPER_PATH=""
  63
  64         Userspace firmware loading is not supported and should
  65         be disabled in the kernel:
  66           CONFIG_FW_LOADER_USER_HELPER=n
  67
  68         Some udev rules and virtualization detection relies on it:
  69           CONFIG_DMIID
  70
  71         Support for some SCSI devices serial number retrieval, to
  72         create additional symlinks in /dev/disk/ and /dev/tape:
  73           CONFIG_BLK_DEV_BSG
  74
  75         Required for PrivateNetwork= and PrivateDevices= in service units:
  76           CONFIG_NET_NS
  77           CONFIG_DEVPTS_MULTIPLE_INSTANCES
  78         Note that systemd-localed.service and other systemd units use
  79         PrivateNetwork and PrivateDevices so this is effectively required.
  80
  81         Required for PrivateUsers= in service units:
  82           CONFIG_USER_NS
  83
  84         Optional but strongly recommended:
  85           CONFIG_IPV6
  86           CONFIG_AUTOFS4_FS
  87           CONFIG_TMPFS_XATTR
  88           CONFIG_{TMPFS,EXT4,XFS,BTRFS_FS,...}_POSIX_ACL
  89           CONFIG_SECCOMP
  90           CONFIG_SECCOMP_FILTER (required for seccomp support)
  91           CONFIG_CHECKPOINT_RESTORE (for the kcmp() syscall)
  92
  93         Required for CPUShares= in resource control unit settings
  94           CONFIG_CGROUP_SCHED
  95           CONFIG_FAIR_GROUP_SCHED
  96
  97         Required for CPUQuota= in resource control unit settings
  98           CONFIG_CFS_BANDWIDTH
  99
 100         For UEFI systems:
 101           CONFIG_EFIVAR_FS
 102           CONFIG_EFI_PARTITION
 103
 104         We recommend to turn off Real-Time group scheduling in the
 105         kernel when using systemd. RT group scheduling effectively
 106         makes RT scheduling unavailable for most userspace, since it
 107         requires explicit assignment of RT budgets to each unit whose
 108         processes making use of RT. As there's no sensible way to
 109         assign these budgets automatically this cannot really be
 110         fixed, and it's best to disable group scheduling hence.
 111            CONFIG_RT_GROUP_SCHED=n
 112
 113         Note that kernel auditing is broken when used with systemd's
 114         container code. When using systemd in conjunction with
 115         containers, please make sure to either turn off auditing at
 116         runtime using the kernel command line option "audit=0", or
 117         turn it off at kernel compile time using:
 118           CONFIG_AUDIT=n
 119         If systemd is compiled with libseccomp support on
 120         architectures which do not use socketcall() and where seccomp
 121         is supported (this effectively means x86-64 and ARM, but
 122         excludes 32-bit x86!), then nspawn will now install a
 123         work-around seccomp filter that makes containers boot even
 124         with audit being enabled. This works correctly only on kernels
 125         3.14 and newer though. TL;DR: turn audit off, still.
 126
 127         glibc >= 2.16
 128         libcap
 129         libmount >= 2.27.1 (from util-linux)
 130                 (util-linux < 2.29 *must* be built with --enable-libmount-force-mountinfo,
 131                  and later versions without --enable-libmount-support-mtab.)
 132         libseccomp >= 2.3.1 (optional)
 133         libblkid >= 2.24 (from util-linux) (optional)
 134         libkmod >= 15 (optional)
 135         PAM >= 1.1.2 (optional)
 136         libcryptsetup (optional)
 137         libaudit (optional)
 138         libacl (optional)
 139         libselinux (optional)
 140         liblzma (optional)
 141         liblz4 >= 119 (optional)
 142         libgcrypt (optional)
 143         libqrencode (optional)
 144         libmicrohttpd (optional)
 145         libpython (optional)
 146         libidn (optional)
 147         elfutils >= 158 (optional)
 148         make, gcc, and similar tools
 149
 150         During runtime, you need the following additional
 151         dependencies:
 152
 153         util-linux >= v2.27.1 required
 154         dbus >= 1.4.0 (strictly speaking optional, but recommended)
 155                 NOTE: If using dbus < 1.9.18, you should override the default
 156                 policy directory (--with-dbuspolicydir=/etc/dbus-1/system.d).
 157         dracut (optional)
 158         PolicyKit (optional)
 159
 160         Two build systems are supported: meson + ninja-build and autools + make.
 161
 162         The following tools are needed with both systems:
 163
 164         pkg-config
 165         gperf >= 3.1
 166         docbook-xsl (optional, required for documentation)
 167         xsltproc    (optional, required for documentation)
 168         python-lxml (optional, required to build the indices)
 169
 170         When building with meson, python and ninja-build are required.
 171
 172         To build in directory build/:
 173           meson build/ && ninja -C build
 174
 175         Any configuration options can be specfied as -Darg=value... arguments
 176         to meson. After the build directory is initially configured, meson will
 177         refuse to run again, and options must be changed with:
 178           mesonconf -Darg=value...
 179         mesonconf without any arguments will print out available options and
 180         their current values.
 181
 182         Useful commands:
 183           ninja -v some/target
 184           ninja test
 185           sudo ninja install
 186           DESTDIR=... ninja install
 187
 188         When building with autotools, the following tools are needed:
 189
 190         automake
 191         autoconf
 192         libtool
 193         intltool
 194         python (optional)
 195
 196         The build system is initialized with ./autogen.sh and the usual
 197           ./configure && make
 198         should be used.
 199
 200         A tar ball can be created with:
 201           git archive --format=tar --prefix=systemd-222/ v222 | xz > systemd-222.tar.xz
 202
 203         When systemd-hostnamed is used, it is strongly recommended to
 204         install nss-myhostname to ensure that, in a world of
 205         dynamically changing hostnames, the hostname stays resolvable
 206         under all circumstances. In fact, systemd-hostnamed will warn
 207         if nss-myhostname is not installed.
 208
 209         Additional packages are necessary to run some tests:
 210         - busybox            (used by test/TEST-13-NSPAWN-SMOKE)
 211         - nc                 (used by test/TEST-12-ISSUE-3171)
 212         - python3-pyparsing
 213         - python3-evdev      (used by hwdb parsing tests)
 214         - strace             (used by test/test-functions)
 215         - capsh              (optional, used by test-execute)
 216
 217 USERS AND GROUPS:
 218         Default udev rules use the following standard system group
 219         names, which need to be resolvable by getgrnam() at any time,
 220         even in the very early boot stages, where no other databases
 221         and network are available:
 222
 223         audio, cdrom, dialout, disk, input, kmem, lp, tape, tty, video
 224
 225         During runtime, the journal daemon requires the
 226         "systemd-journal" system group to exist. New journal files will
 227         be readable by this group (but not writable), which may be used
 228         to grant specific users read access. In addition, system
 229         groups "wheel" and "adm" will be given read-only access to
 230         journal files using systemd-tmpfiles.service.
 231
 232         The journal gateway daemon requires the
 233         "systemd-journal-gateway" system user and group to
 234         exist. During execution this network facing service will drop
 235         privileges and assume this uid/gid for security reasons.
 236
 237         Similarly, the NTP daemon requires the "systemd-timesync" system
 238         user and group to exist.
 239
 240         Similarly, the network management daemon requires the
 241         "systemd-network" system user and group to exist.
 242
 243         Similarly, the name resolution daemon requires the
 244         "systemd-resolve" system user and group to exist.
 245
 246         Similarly, the coredump support requires the
 247         "systemd-coredump" system user and group to exist.
 248
 249 NSS:
 250         systemd ships with four glibc NSS modules:
 251
 252         nss-myhostname resolves the local hostname to locally
 253         configured IP addresses, as well as "localhost" to
 254         127.0.0.1/::1.
 255
 256         nss-resolve enables DNS resolution via the systemd-resolved
 257         DNS/LLMNR caching stub resolver "systemd-resolved".
 258
 259         nss-mymachines enables resolution of all local containers registered
 260         with machined to their respective IP addresses. It also maps UID/GIDs
 261         ranges used by containers to useful names.
 262
 263         nss-systemd enables resolution of all dynamically allocated service
 264         users. (See the DynamicUser= setting in unit files.)
 265
 266         To make use of these NSS modules, please add them to the "hosts:",
 267         "passwd:" and "group:" lines in /etc/nsswitch.conf. The "resolve"
 268         module should replace the glibc "dns" module in this file (and don't
 269         worry, it chain-loads the "dns" module if it can't talk to resolved).
 270
 271         The four modules should be used in the following order:
 272
 273                 passwd: compat mymachines systemd
 274                 group: compat mymachines systemd
 275                 hosts: files mymachines resolve myhostname
 276
 277 SYSV INIT.D SCRIPTS:
 278         When calling "systemctl enable/disable/is-enabled" on a unit which is a
 279         SysV init.d script, it calls /usr/lib/systemd/systemd-sysv-install;
 280         this needs to translate the action into the distribution specific
 281         mechanism such as chkconfig or update-rc.d. Packagers need to provide
 282         this script if you need this functionality (you don't if you disabled
 283         SysV init support).
 284
 285         Please see src/systemctl/systemd-sysv-install.SKELETON for how this
 286         needs to look like, and provide an implementation at the marked places.
 287
 288 WARNINGS:
 289         systemd will warn you during boot if /usr is on a different
 290         file system than /. While in systemd itself very little will
 291         break if /usr is on a separate partition, many of its
 292         dependencies very likely will break sooner or later in one
 293         form or another. For example, udev rules tend to refer to
 294         binaries in /usr, binaries that link to libraries in /usr or
 295         binaries that refer to data files in /usr. Since these
 296         breakages are not always directly visible, systemd will warn
 297         about this, since this kind of file system setup is not really
 298         supported anymore by the basic set of Linux OS components.
 299
 300         systemd requires that the /run mount point exists. systemd also
 301         requires that /var/run is a symlink to /run.
 302
 303         For more information on this issue consult
 304         https://www.freedesktop.org/wiki/Software/systemd/separate-usr-is-broken
 305
 306         To run systemd under valgrind, compile with VALGRIND defined
 307         (e.g. ./configure CPPFLAGS='... -DVALGRIND=1'). Otherwise,
 308         false positives will be triggered by code which violates
 309         some rules but is actually safe.
 310
 311 ENGINEERING AND CONSULTING SERVICES:
 312         Kinvolk (https://kinvolk.io) offers professional engineering
 313         and consulting services for systemd. Please contact Chris Kühl
 314         <chris@kinvolk.io> for more information.