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 >= 3.12
  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         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 *must* be built with --enable-libmount-force-mountinfo)
 131         libseccomp >= 2.3.1 (optional)
 132         libblkid >= 2.24 (from util-linux) (optional)
 133         libkmod >= 15 (optional)
 134         PAM >= 1.1.2 (optional)
 135         libcryptsetup (optional)
 136         libaudit (optional)
 137         libacl (optional)
 138         libselinux (optional)
 139         liblzma (optional)
 140         liblz4 >= 119 (optional)
 141         libgcrypt (optional)
 142         libqrencode (optional)
 143         libmicrohttpd (optional)
 144         libpython (optional)
 145         libidn (optional)
 146         elfutils >= 158 (optional)
 147         make, gcc, and similar tools
 148
 149         During runtime, you need the following additional
 150         dependencies:
 151
 152         util-linux >= v2.27.1 required
 153         dbus >= 1.4.0 (strictly speaking optional, but recommended)
 154                 NOTE: If using dbus < 1.9.18, you should override the default
 155                 policy directory (--with-dbuspolicydir=/etc/dbus-1/system.d).
 156         dracut (optional)
 157         PolicyKit (optional)
 158
 159         When building from git, the following tools are needed:
 160
 161         pkg-config
 162         docbook-xsl
 163         xsltproc
 164         automake
 165         autoconf
 166         libtool
 167         intltool
 168         gperf
 169         python (optional)
 170         python-lxml (optional, but required to build the indices)
 171
 172         The build system is initialized with ./autogen.sh. A tar ball
 173         can be created with:
 174           git archive --format=tar --prefix=systemd-222/ v222 | xz > systemd-222.tar.xz
 175
 176         When systemd-hostnamed is used, it is strongly recommended to
 177         install nss-myhostname to ensure that, in a world of
 178         dynamically changing hostnames, the hostname stays resolvable
 179         under all circumstances. In fact, systemd-hostnamed will warn
 180         if nss-myhostname is not installed.
 181
 182         Additional packages are necessary to run some tests:
 183         - busybox            (used by test/TEST-13-NSPAWN-SMOKE)
 184         - nc                 (used by test/TEST-12-ISSUE-3171)
 185         - python3-pyparsing
 186         - python3-evdev      (used by hwdb parsing tests)
 187         - strace             (used by test/test-functions)
 188         - capsh              (optional, used by test-execute)
 189
 190 USERS AND GROUPS:
 191         Default udev rules use the following standard system group
 192         names, which need to be resolvable by getgrnam() at any time,
 193         even in the very early boot stages, where no other databases
 194         and network are available:
 195
 196         audio, cdrom, dialout, disk, input, kmem, lp, tape, tty, video
 197
 198         During runtime, the journal daemon requires the
 199         "systemd-journal" system group to exist. New journal files will
 200         be readable by this group (but not writable), which may be used
 201         to grant specific users read access. In addition, system
 202         groups "wheel" and "adm" will be given read-only access to
 203         journal files using systemd-tmpfiles.service.
 204
 205         The journal gateway daemon requires the
 206         "systemd-journal-gateway" system user and group to
 207         exist. During execution this network facing service will drop
 208         privileges and assume this uid/gid for security reasons.
 209
 210         Similarly, the NTP daemon requires the "systemd-timesync" system
 211         user and group to exist.
 212
 213         Similarly, the network management daemon requires the
 214         "systemd-network" system user and group to exist.
 215
 216         Similarly, the name resolution daemon requires the
 217         "systemd-resolve" system user and group to exist.
 218
 219         Similarly, the coredump support requires the
 220         "systemd-coredump" system user and group to exist.
 221
 222 NSS:
 223         systemd ships with four glibc NSS modules:
 224
 225         nss-myhostname resolves the local hostname to locally
 226         configured IP addresses, as well as "localhost" to
 227         127.0.0.1/::1.
 228
 229         nss-resolve enables DNS resolution via the systemd-resolved
 230         DNS/LLMNR caching stub resolver "systemd-resolved".
 231
 232         nss-mymachines enables resolution of all local containers registered
 233         with machined to their respective IP addresses. It also maps UID/GIDs
 234         ranges used by containers to useful names.
 235
 236         nss-systemd enables resolution of all dynamically allocated service
 237         users. (See the DynamicUser= setting in unit files.)
 238
 239         To make use of these NSS modules, please add them to the "hosts:",
 240         "passwd:" and "group:" lines in /etc/nsswitch.conf. The "resolve"
 241         module should replace the glibc "dns" module in this file (and don't
 242         worry, it chain-loads the "dns" module if it can't talk to resolved).
 243
 244         The four modules should be used in the following order:
 245
 246                 passwd: compat mymachines systemd
 247                 group: compat mymachines systemd
 248                 hosts: files mymachines resolve myhostname
 249
 250 SYSV INIT.D SCRIPTS:
 251         When calling "systemctl enable/disable/is-enabled" on a unit which is a
 252         SysV init.d script, it calls /usr/lib/systemd/systemd-sysv-install;
 253         this needs to translate the action into the distribution specific
 254         mechanism such as chkconfig or update-rc.d. Packagers need to provide
 255         this script if you need this functionality (you don't if you disabled
 256         SysV init support).
 257
 258         Please see src/systemctl/systemd-sysv-install.SKELETON for how this
 259         needs to look like, and provide an implementation at the marked places.
 260
 261 WARNINGS:
 262         systemd will warn you during boot if /usr is on a different
 263         file system than /. While in systemd itself very little will
 264         break if /usr is on a separate partition, many of its
 265         dependencies very likely will break sooner or later in one
 266         form or another. For example, udev rules tend to refer to
 267         binaries in /usr, binaries that link to libraries in /usr or
 268         binaries that refer to data files in /usr. Since these
 269         breakages are not always directly visible, systemd will warn
 270         about this, since this kind of file system setup is not really
 271         supported anymore by the basic set of Linux OS components.
 272
 273         systemd requires that the /run mount point exists. systemd also
 274         requires that /var/run is a symlink to /run.
 275
 276         For more information on this issue consult
 277         https://www.freedesktop.org/wiki/Software/systemd/separate-usr-is-broken
 278
 279         To run systemd under valgrind, compile with VALGRIND defined
 280         (e.g. ./configure CPPFLAGS='... -DVALGRIND=1'). Otherwise,
 281         false positives will be triggered by code which violates
 282         some rules but is actually safe.
 283
 284 ENGINEERING AND CONSULTING SERVICES:
 285         Kinvolk (https://kinvolk.io) offers professional engineering
 286         and consulting services for systemd. Please contact Chris Kühl
 287         <chris@kinvolk.io> for more information.