конфигурация целевого устройства (Target unit configuration)
Имя (Name)
systemd.target - Target unit configuration
Синопсис (Synopsis)
target.target
Описание (Description)
A unit configuration file whose name ends in ".target" encodes
information about a target unit of systemd, which is used for
grouping units and as well-known synchronization points during
start-up.
This unit type has no specific options. See systemd.unit(5) for
the common options of all unit configuration files. The common
configuration items are configured in the generic [Unit] and
[Install] sections. A separate [Target] section does not exist,
since no target-specific options may be configured.
Target units do not offer any additional functionality on top of
the generic functionality provided by units. They exist merely to
group units via dependencies (useful as boot targets), and to
establish standardized names for synchronization points used in
dependencies between units. Among other things, target units are
a more flexible replacement for SysV runlevels in the classic
SysV init system. (And for compatibility reasons special target
units such as runlevel3.target exist which are used by the SysV
runlevel compatibility code in systemd. See systemd.special(7)
for details).
Автоматические зависимости (Automatic dependencies)
Implicit Dependencies
There are no implicit dependencies for target units.
Default Dependencies
The following dependencies are added unless
DefaultDependencies=no is set:
• Target units will automatically complement all configured
dependencies of type Wants= or Requires= with dependencies of
type After= unless DefaultDependencies=no is set in the
specified units. Note that Wants= or Requires= must be
defined in the target unit itself — if you for example define
Wants=some.target in some.service, the automatic ordering
will not be added.
• Target units automatically gain Conflicts= and Before=
dependencies against shutdown.target.
Примеры (Examples)
Example 1. Simple standalone target
# emergency-net.target
[Unit]
Description=Emergency Mode with Networking
Requires=emergency.target systemd-networkd.service
After=emergency.target systemd-networkd.service
AllowIsolate=yes
When adding dependencies to other units, it's important to check
if they set DefaultDependencies=. Service units, unless they set
DefaultDependencies=no, automatically get a dependency on
sysinit.target. In this case, both emergency.target and
systemd-networkd.service have DefaultDependencies=no, so they are
suitable for use in this target, and do not pull in
sysinit.target.
You can now switch into this emergency mode by running systemctl
isolate emergency-net.target or by passing the option
systemd.unit=emergency-net.target on the kernel command line.
Other units can have WantedBy=emergency-net.target in the
[Install] section. After they are enabled using systemctl enable,
they will be started before emergency-net.target is started. It
is also possible to add arbitrary units as dependencies of
emergency.target without modifying them by using systemctl
add-wants.
Смотри также (See also)
systemd(1), systemctl(1), systemd.unit(5), systemd.special(7),
systemd.directives(7)
