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