1.4. Important [Unit] section options

The following tables lists important options of the [Unit] section.

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表 1.2. Important [Unit] section options
Option ^[a]	Description
`Description`	A meaningful description of the unit. This text is displayed for example in the output of the `systemctl status` command.
`Documentation`	Provides a list of URIs referencing documentation for the unit.
`After`^[b]	Defines the order in which units are started. The unit starts only after the units specified in `After` are active. Unlike `Requires`, `After` does not explicitly activate the specified units. The `Before` option has the opposite functionality to `After`.
`Requires`	Configures dependencies on other units. The units listed in `Requires` are activated together with the unit. If any of the required units fail to start, the unit is not activated.
`Wants`	Configures weaker dependencies than `Requires`. If any of the listed units does not start successfully, it has no impact on the unit activation. This is the recommended way to establish custom unit dependencies.
`Conflicts`	Configures negative dependencies, an opposite to `Requires`.
^[a] For a complete list of options configurable in the [Unit] section, see the `systemd.unit(5)` manual page. ^[b] In most cases, it is sufficient to set only the ordering dependencies with `After` and `Before` unit file options. If you also set a requirement dependency with `Wants` (recommended) or `Requires`, the ordering dependency still needs to be specified. That is because ordering and requirement dependencies work independently from each other.