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
  12
  13 MAILING LIST:
  14         https://lists.freedesktop.org/mailman/listinfo/systemd-devel
  15
  16 IRC:
  17         #systemd on irc.freenode.org
  18
  19 BUG REPORTS:
  20         https://github.com/systemd/systemd/issues
  21
  22 AUTHOR:
  23         Lennart Poettering
  24         Kay Sievers
  25         ...and many others
  26
  27 LICENSE:
  28         LGPLv2.1+ for all code
  29         - except src/basic/MurmurHash2.c which is Public Domain
  30         - except src/basic/siphash24.c which is CC0 Public Domain
  31         - except src/journal/lookup3.c which is Public Domain
  32         - except src/udev/* which is (currently still) GPLv2, GPLv2+
  33         - except tools/chromiumos/* which is BSD-style
  34
  35 REQUIREMENTS:
  36         Linux kernel >= 3.13
  37         Linux kernel >= 4.2 for unified cgroup hierarchy support
  38         Linux kernel >= 5.4 for signed Verity images support
  39
  40         Kernel Config Options:
  41           CONFIG_DEVTMPFS
  42           CONFIG_CGROUPS (it is OK to disable all controllers)
  43           CONFIG_INOTIFY_USER
  44           CONFIG_SIGNALFD
  45           CONFIG_TIMERFD
  46           CONFIG_EPOLL
  47           CONFIG_NET
  48           CONFIG_SYSFS
  49           CONFIG_PROC_FS
  50           CONFIG_FHANDLE (libudev, mount and bind mount handling)
  51
  52         Kernel crypto/hash API
  53           CONFIG_CRYPTO_USER_API_HASH
  54           CONFIG_CRYPTO_HMAC
  55           CONFIG_CRYPTO_SHA256
  56
  57         udev will fail to work with the legacy sysfs layout:
  58           CONFIG_SYSFS_DEPRECATED=n
  59
  60         Legacy hotplug slows down the system and confuses udev:
  61           CONFIG_UEVENT_HELPER_PATH=""
  62
  63         Userspace firmware loading is not supported and should
  64         be disabled in the kernel:
  65           CONFIG_FW_LOADER_USER_HELPER=n
  66
  67         Some udev rules and virtualization detection relies on it:
  68           CONFIG_DMIID
  69
  70         Support for some SCSI devices serial number retrieval, to
  71         create additional symlinks in /dev/disk/ and /dev/tape:
  72           CONFIG_BLK_DEV_BSG
  73
  74         Required for PrivateNetwork= in service units:
  75           CONFIG_NET_NS
  76         Note that systemd-localed.service and other systemd units use
  77         PrivateNetwork so this is effectively required.
  78
  79         Required for PrivateUsers= in service units:
  80           CONFIG_USER_NS
  81
  82         Optional but strongly recommended:
  83           CONFIG_IPV6
  84           CONFIG_AUTOFS4_FS
  85           CONFIG_TMPFS_XATTR
  86           CONFIG_{TMPFS,EXT4_FS,XFS,BTRFS_FS,...}_POSIX_ACL
  87           CONFIG_SECCOMP
  88           CONFIG_SECCOMP_FILTER (required for seccomp support)
  89           CONFIG_CHECKPOINT_RESTORE (for the kcmp() syscall)
  90
  91         Required for CPUShares= in resource control unit settings
  92           CONFIG_CGROUP_SCHED
  93           CONFIG_FAIR_GROUP_SCHED
  94
  95         Required for CPUQuota= in resource control unit settings
  96           CONFIG_CFS_BANDWIDTH
  97
  98         Required for IPAddressDeny= and IPAddressAllow= in resource control
  99         unit settings
 100           CONFIG_CGROUP_BPF
 101
 102         For UEFI systems:
 103           CONFIG_EFIVAR_FS
 104           CONFIG_EFI_PARTITION
 105
 106         Required for signed Verity images support:
 107           CONFIG_DM_VERITY_VERIFY_ROOTHASH_SIG
 108
 109         We recommend to turn off Real-Time group scheduling in the
 110         kernel when using systemd. RT group scheduling effectively
 111         makes RT scheduling unavailable for most userspace, since it
 112         requires explicit assignment of RT budgets to each unit whose
 113         processes making use of RT. As there's no sensible way to
 114         assign these budgets automatically this cannot really be
 115         fixed, and it's best to disable group scheduling hence.
 116            CONFIG_RT_GROUP_SCHED=n
 117
 118         It's a good idea to disable the implicit creation of networking bonding
 119         devices by the kernel networking bonding module, so that the
 120         automatically created "bond0" interface doesn't conflict with any such
 121         device created by systemd-networkd (or other tools). Ideally there
 122         would be a kernel compile-time option for this, but there currently
 123         isn't. The next best thing is to make this change through a modprobe.d
 124         drop-in. This is shipped by default, see modprobe.d/systemd.conf.
 125
 126         Required for systemd-nspawn:
 127           CONFIG_DEVPTS_MULTIPLE_INSTANCES or Linux kernel >= 4.7
 128
 129         Note that kernel auditing is broken when used with systemd's
 130         container code. When using systemd in conjunction with
 131         containers, please make sure to either turn off auditing at
 132         runtime using the kernel command line option "audit=0", or
 133         turn it off at kernel compile time using:
 134           CONFIG_AUDIT=n
 135         If systemd is compiled with libseccomp support on
 136         architectures which do not use socketcall() and where seccomp
 137         is supported (this effectively means x86-64 and ARM, but
 138         excludes 32-bit x86!), then nspawn will now install a
 139         work-around seccomp filter that makes containers boot even
 140         with audit being enabled. This works correctly only on kernels
 141         3.14 and newer though. TL;DR: turn audit off, still.
 142
 143         glibc >= 2.16
 144         libcap
 145         libmount >= 2.30 (from util-linux)
 146                 (util-linux *must* be built without --enable-libmount-support-mtab)
 147         libseccomp >= 2.3.1 (optional)
 148         libblkid >= 2.24 (from util-linux) (optional)
 149         libkmod >= 15 (optional)
 150         PAM >= 1.1.2 (optional)
 151         libcryptsetup (optional), >= 2.3.0 required for signed Verity images support
 152         libaudit (optional)
 153         libacl (optional)
 154         libselinux (optional)
 155         liblzma (optional)
 156         liblz4 >= 1.3.0 / 130 (optional)
 157         libzstd >= 1.4.0 (optional)
 158         libgcrypt (optional)
 159         libqrencode (optional)
 160         libmicrohttpd (optional)
 161         libpython (optional)
 162         libidn2 or libidn (optional)
 163         gnutls >= 3.1.4 (optional, >= 3.6.0 is required to support DNS-over-TLS with gnutls)
 164         openssl >= 1.1.0 (optional, required to support DNS-over-TLS with openssl)
 165         elfutils >= 158 (optional)
 166         polkit (optional)
 167         tzdata >= 2014f (optional)
 168         pkg-config
 169         gperf
 170         docbook-xsl (optional, required for documentation)
 171         xsltproc    (optional, required for documentation)
 172         python-lxml (optional, required to build the indices)
 173         python >= 3.5
 174         meson >= 0.46 (>= 0.49 is required to build position-independent executables)
 175         ninja
 176         gcc, awk, sed, grep, m4, and similar tools
 177
 178         During runtime, you need the following additional
 179         dependencies:
 180
 181         util-linux >= v2.27.1 required
 182         dbus >= 1.4.0 (strictly speaking optional, but recommended)
 183                 NOTE: If using dbus < 1.9.18, you should override the default
 184                 policy directory (--with-dbuspolicydir=/etc/dbus-1/system.d).
 185         dracut (optional)
 186         polkit (optional)
 187
 188         To build in directory build/:
 189           meson build/ && ninja -C build
 190
 191         Any configuration options can be specified as -Darg=value... arguments
 192         to meson. After the build directory is initially configured, meson will
 193         refuse to run again, and options must be changed with:
 194           mesonconf -Darg=value...
 195         mesonconf without any arguments will print out available options and
 196         their current values.
 197
 198         Useful commands:
 199           ninja -v some/target
 200           ninja test
 201           sudo ninja install
 202           DESTDIR=... ninja install
 203
 204         A tarball can be created with:
 205           git archive --format=tar --prefix=systemd-222/ v222 | xz > systemd-222.tar.xz
 206
 207         When systemd-hostnamed is used, it is strongly recommended to
 208         install nss-myhostname to ensure that, in a world of
 209         dynamically changing hostnames, the hostname stays resolvable
 210         under all circumstances. In fact, systemd-hostnamed will warn
 211         if nss-myhostname is not installed.
 212
 213         nss-systemd must be enabled on systemd systems, as that's required for
 214         DynamicUser= to work. Note that we ship services out-of-the-box that
 215         make use of DynamicUser= now, hence enabling nss-systemd is not
 216         optional.
 217
 218         Note that the build prefix for systemd must be /usr. (Moreover,
 219         packages systemd relies on — such as D-Bus — really should use the same
 220         prefix, otherwise you are on your own.) -Dsplit-usr=false (which is the
 221         default and does not need to be specified) is the recommended setting,
 222         and -Dsplit-usr=true should be used on systems which have /usr on a
 223         separate partition.
 224
 225         Additional packages are necessary to run some tests:
 226         - busybox            (used by test/TEST-13-NSPAWN-SMOKE)
 227         - nc                 (used by test/TEST-12-ISSUE-3171)
 228         - python3-pyparsing
 229         - python3-evdev      (used by hwdb parsing tests)
 230         - strace             (used by test/test-functions)
 231         - capsh              (optional, used by test-execute)
 232
 233 USERS AND GROUPS:
 234         Default udev rules use the following standard system group
 235         names, which need to be resolvable by getgrnam() at any time,
 236         even in the very early boot stages, where no other databases
 237         and network are available:
 238
 239         audio, cdrom, dialout, disk, input, kmem, kvm, lp, render, tape, tty, video
 240
 241         During runtime, the journal daemon requires the
 242         "systemd-journal" system group to exist. New journal files will
 243         be readable by this group (but not writable), which may be used
 244         to grant specific users read access. In addition, system
 245         groups "wheel" and "adm" will be given read-only access to
 246         journal files using systemd-tmpfiles.service.
 247
 248         The journal remote daemon requires the
 249         "systemd-journal-remote" system user and group to
 250         exist. During execution this network facing service will drop
 251         privileges and assume this uid/gid for security reasons.
 252
 253         Similarly, the network management daemon requires the
 254         "systemd-network" system user and group to exist.
 255
 256         Similarly, the name resolution daemon requires the
 257         "systemd-resolve" system user and group to exist.
 258
 259         Similarly, the coredump support requires the
 260         "systemd-coredump" system user and group to exist.
 261
 262 NSS:
 263         systemd ships with four glibc NSS modules:
 264
 265         nss-myhostname resolves the local hostname to locally configured IP
 266         addresses, as well as "localhost" to 127.0.0.1/::1.
 267
 268         nss-resolve enables DNS resolution via the systemd-resolved DNS/LLMNR
 269         caching stub resolver "systemd-resolved".
 270
 271         nss-mymachines enables resolution of all local containers registered
 272         with machined to their respective IP addresses.
 273
 274         nss-systemd enables resolution of users/group registered via the
 275         User/Group Record Lookup API (https://systemd.io/USER_GROUP_API/),
 276         including all dynamically allocated service users. (See the
 277         DynamicUser= setting in unit files.)
 278
 279         To make use of these NSS modules, please add them to the "hosts:",
 280         "passwd:" and "group:" lines in /etc/nsswitch.conf. The "resolve"
 281         module should replace the glibc "dns" module in this file (and don't
 282         worry, it chain-loads the "dns" module if it can't talk to resolved).
 283
 284         The four modules should be used in the following order:
 285
 286                 passwd: compat systemd
 287                 group: compat systemd
 288                 hosts: files mymachines resolve [!UNAVAIL=return] dns myhostname
 289
 290 SYSV INIT.D SCRIPTS:
 291         When calling "systemctl enable/disable/is-enabled" on a unit which is a
 292         SysV init.d script, it calls /usr/lib/systemd/systemd-sysv-install;
 293         this needs to translate the action into the distribution specific
 294         mechanism such as chkconfig or update-rc.d. Packagers need to provide
 295         this script if you need this functionality (you don't if you disabled
 296         SysV init support).
 297
 298         Please see src/systemctl/systemd-sysv-install.SKELETON for how this
 299         needs to look like, and provide an implementation at the marked places.
 300
 301 WARNINGS:
 302         systemd will warn during early boot if /usr is not already mounted at
 303         this point (that means: either located on the same file system as / or
 304         already mounted in the initrd). While in systemd itself very little
 305         will break if /usr is on a separate, late-mounted partition, many of
 306         its dependencies very likely will break sooner or later in one form or
 307         another. For example, udev rules tend to refer to binaries in /usr,
 308         binaries that link to libraries in /usr or binaries that refer to data
 309         files in /usr. Since these breakages are not always directly visible,
 310         systemd will warn about this, since this kind of file system setup is
 311         not really supported anymore by the basic set of Linux OS components.
 312
 313         systemd requires that the /run mount point exists. systemd also
 314         requires that /var/run is a symlink to /run.
 315
 316         For more information on this issue consult
 317         https://www.freedesktop.org/wiki/Software/systemd/separate-usr-is-broken
 318
 319         To run systemd under valgrind, compile with meson option
 320         -Dvalgrind=true and have valgrind development headers installed
 321         (i.e. valgrind-devel or equivalent). Otherwise, false positives will be
 322         triggered by code which violates some rules but is actually safe. Note
 323         that valgrind generates nice output only on exit(), hence on shutdown
 324         we don't execve() systemd-shutdown.
 325
 326 STABLE BRANCHES AND BACKPORTS:
 327        Stable branches with backported patches are available in the
 328        systemd-stable repo at https://github.com/systemd/systemd-stable.
 329
 330        Stable branches are started for certain releases of systemd and named
 331        after them, e.g. v238-stable. Stable branches are managed by
 332        distribution maintainers on an as needed basis. See
 333        https://www.freedesktop.org/wiki/Software/systemd/Backports/ for some
 334        more information and examples.
 335
 336 ENGINEERING AND CONSULTING SERVICES:
 337         Kinvolk (https://kinvolk.io) offers professional engineering
 338         and consulting services for systemd. Please contact Chris Kühl
 339         <chris@kinvolk.io> for more information.