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         http://lists.freedesktop.org/mailman/listinfo/systemd-commits
  19
  20 IRC:
  21         #systemd on irc.freenode.org
  22
  23 BUG REPORTS:
  24         https://github.com/systemd/systemd/issues
  25
  26 AUTHOR:
  27         Lennart Poettering
  28         Kay Sievers
  29         ...and many others
  30
  31 LICENSE:
  32         LGPLv2.1+ for all code
  33         - except src/basic/MurmurHash2.c which is Public Domain
  34         - except src/basic/siphash24.c which is CC0 Public Domain
  35         - except src/journal/lookup3.c which is Public Domain
  36         - except src/udev/* which is (currently still) GPLv2, GPLv2+
  37
  38 REQUIREMENTS:
  39         Linux kernel >= 3.11
  40         Linux kernel >= 4.2 for unified cgroup hierarchy support
  41
  42         Kernel Config Options:
  43           CONFIG_DEVTMPFS
  44           CONFIG_CGROUPS (it is OK to disable all controllers)
  45           CONFIG_INOTIFY_USER
  46           CONFIG_SIGNALFD
  47           CONFIG_TIMERFD
  48           CONFIG_EPOLL
  49           CONFIG_NET
  50           CONFIG_SYSFS
  51           CONFIG_PROC_FS
  52           CONFIG_FHANDLE (libudev, mount and bind mount handling)
  53
  54         udev will fail to work with the legacy sysfs layout:
  55           CONFIG_SYSFS_DEPRECATED=n
  56
  57         Legacy hotplug slows down the system and confuses udev:
  58           CONFIG_UEVENT_HELPER_PATH=""
  59
  60         Userspace firmware loading is not supported and should
  61         be disabled in the kernel:
  62           CONFIG_FW_LOADER_USER_HELPER=n
  63
  64         Some udev rules and virtualization detection relies on it:
  65           CONFIG_DMIID
  66
  67         Support for some SCSI devices serial number retrieval, to
  68         create additional symlinks in /dev/disk/ and /dev/tape:
  69           CONFIG_BLK_DEV_BSG
  70
  71         Required for PrivateNetwork and PrivateDevices in service units:
  72           CONFIG_NET_NS
  73           CONFIG_DEVPTS_MULTIPLE_INSTANCES
  74         Note that systemd-localed.service and other systemd units use
  75         PrivateNetwork and PrivateDevices so this is effectively required.
  76
  77         Optional but strongly recommended:
  78           CONFIG_IPV6
  79           CONFIG_AUTOFS4_FS
  80           CONFIG_TMPFS_XATTR
  81           CONFIG_{TMPFS,EXT4,XFS,BTRFS_FS,...}_POSIX_ACL
  82           CONFIG_SECCOMP
  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 systemd-bootchart, several proc debug interfaces are required:
  93           CONFIG_SCHEDSTATS
  94           CONFIG_SCHED_DEBUG
  95
  96         For UEFI systems:
  97           CONFIG_EFIVAR_FS
  98           CONFIG_EFI_PARTITION
  99
 100         We recommend to turn off Real-Time group scheduling in the
 101         kernel when using systemd. RT group scheduling effectively
 102         makes RT scheduling unavailable for most userspace, since it
 103         requires explicit assignment of RT budgets to each unit whose
 104         processes making use of RT. As there's no sensible way to
 105         assign these budgets automatically this cannot really be
 106         fixed, and it's best to disable group scheduling hence.
 107            CONFIG_RT_GROUP_SCHED=n
 108
 109         Note that kernel auditing is broken when used with systemd's
 110         container code. When using systemd in conjunction with
 111         containers, please make sure to either turn off auditing at
 112         runtime using the kernel command line option "audit=0", or
 113         turn it off at kernel compile time using:
 114           CONFIG_AUDIT=n
 115         If systemd is compiled with libseccomp support on
 116         architectures which do not use socketcall() and where seccomp
 117         is supported (this effectively means x86-64 and ARM, but
 118         excludes 32-bit x86!), then nspawn will now install a
 119         work-around seccomp filter that makes containers boot even
 120         with audit being enabled. This works correctly only on kernels
 121         3.14 and newer though. TL;DR: turn audit off, still.
 122
 123         glibc >= 2.16
 124         libcap
 125         libmount >= 2.27.1 (from util-linux)
 126         libseccomp >= 1.0.0 (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         dracut (optional)
 150         PolicyKit (optional)
 151
 152         When building from git, the following tools are needed:
 153
 154         pkg-config
 155         docbook-xsl
 156         xsltproc
 157         automake
 158         autoconf
 159         libtool
 160         intltool
 161         gperf
 162         python (optional)
 163         python-lxml (optional, but required to build the indices)
 164
 165         The build system is initialized with ./autogen.sh. A tar ball
 166         can be created with:
 167           git archive --format=tar --prefix=systemd-222/ v222 | xz > systemd-222.tar.xz
 168
 169         When systemd-hostnamed is used, it is strongly recommended to
 170         install nss-myhostname to ensure that, in a world of
 171         dynamically changing hostnames, the hostname stays resolvable
 172         under all circumstances. In fact, systemd-hostnamed will warn
 173         if nss-myhostname is not installed.
 174
 175 USERS AND GROUPS:
 176         Default udev rules use the following standard system group
 177         names, which need to be resolvable by getgrnam() at any time,
 178         even in the very early boot stages, where no other databases
 179         and network are available:
 180
 181         audio, cdrom, dialout, disk, input, kmem, lp, tape, tty, video
 182
 183         During runtime, the journal daemon requires the
 184         "systemd-journal" system group to exist. New journal files will
 185         be readable by this group (but not writable), which may be used
 186         to grant specific users read access. In addition, system
 187         groups "wheel" and "adm" will be given read-only access to
 188         journal files using systemd-tmpfiles.service.
 189
 190         The journal gateway daemon requires the
 191         "systemd-journal-gateway" system user and group to
 192         exist. During execution this network facing service will drop
 193         privileges and assume this uid/gid for security reasons.
 194
 195         Similarly, the NTP daemon requires the "systemd-timesync" system
 196         user and group to exist.
 197
 198         Similarly, the network management daemon requires the
 199         "systemd-network" system user and group to exist.
 200
 201         Similarly, the name resolution daemon requires the
 202         "systemd-resolve" system user and group to exist.
 203
 204         Similarly, the kdbus dbus1 proxy daemon requires the
 205         "systemd-bus-proxy" system user and group to exist.
 206
 207 NSS:
 208         systemd ships with three NSS modules:
 209
 210         nss-myhostname resolves the local hostname to locally
 211         configured IP addresses, as well as "localhost" to
 212         127.0.0.1/::1.
 213
 214         nss-resolve enables DNS resolution via the systemd-resolved
 215         DNS/LLMNR caching stub resolver "systemd-resolved".
 216
 217         nss-mymachines enables resolution of all local containers
 218         registered with machined to their respective IP addresses.
 219
 220         To make use of these NSS modules, please add them to the
 221         "hosts: " line in /etc/nsswitch.conf. The "resolve" module
 222         should replace the glibc "dns" module in this file.
 223
 224         The three modules should be used in the following order:
 225
 226                 hosts: files mymachines resolve myhostname
 227
 228 SYSV INIT.D SCRIPTS:
 229         When calling "systemctl enable/disable/is-enabled" on a unit which is a
 230         SysV init.d script, it calls /usr/lib/systemd/systemd-sysv-install;
 231         this needs to translate the action into the distribution specific
 232         mechanism such as chkconfig or update-rc.d. Packagers need to provide
 233         this script if you need this functionality (you don't if you disabled
 234         SysV init support).
 235
 236         Please see src/systemctl/systemd-sysv-install.SKELETON for how this
 237         needs to look like, and provide an implementation at the marked places.
 238
 239 WARNINGS:
 240         systemd will freeze execution during boot if /etc/mtab exists
 241         but is not a symlink to /proc/mounts. Please ensure that
 242         /etc/mtab is a proper symlink.
 243
 244         systemd will warn you during boot if /usr is on a different
 245         file system than /. While in systemd itself very little will
 246         break if /usr is on a separate partition, many of its
 247         dependencies very likely will break sooner or later in one
 248         form or another. For example, udev rules tend to refer to
 249         binaries in /usr, binaries that link to libraries in /usr or
 250         binaries that refer to data files in /usr. Since these
 251         breakages are not always directly visible, systemd will warn
 252         about this, since this kind of file system setup is not really
 253         supported anymore by the basic set of Linux OS components.
 254
 255         systemd requires that the /run mount point exists. systemd also
 256         requires that /var/run is a symlink to /run.
 257
 258         For more information on this issue consult
 259         http://freedesktop.org/wiki/Software/systemd/separate-usr-is-broken
 260
 261         To run systemd under valgrind, compile with VALGRIND defined
 262         (e.g. ./configure CPPFLAGS='... -DVALGRIND=1'). Otherwise,
 263         false positives will be triggered by code which violates
 264         some rules but is actually safe.
 265
 266         Currently, systemd-timesyncd defaults to use the Google NTP
 267         servers if not specified otherwise at configure time. You
 268         really should not ship an OS or device with this default
 269         setting. See DISTRO_PORTING for details.