12.9 服务

An important part of preparing an operating-system declaration is listing system services and their configuration (see 使用配置系统). System services are typically daemons launched when the system boots, or other actions needed at that time—e.g., configuring network access.

Guix has a broad definition of “service” (see 合成服务), but many services are managed by the GNU Shepherd (see Shepherd服务). On a running system, the herd command allows you to list the available services, show their status, start and stop them, or do other specific operations (see Jump Start in The GNU Shepherd Manual). For example:

# herd status

The above command, run as root, lists the currently defined services. The herd doc command shows a synopsis of the given service and its associated actions:

# herd doc nscd
Run libc's name service cache daemon (nscd).

# herd doc nscd action invalidate
invalidate: Invalidate the given cache--e.g., 'hosts' for host name lookups.

The start, stop, and restart sub-commands have the effect you would expect. For instance, the commands below stop the nscd service and restart the Xorg display server:

# herd stop nscd
Service nscd has been stopped.
# herd restart xorg-server
Service xorg-server has been stopped.
Service xorg-server has been started.

For some services, herd configuration returns the name of the service’s configuration file, which can be handy to inspect its configuration:

# herd configuration sshd
/gnu/store/…-sshd_config

The following sections document the available services, starting with the core services, that may be used in an operating-system declaration.