Definition
The hub is a virtual filesystem that represents a realm and contains relevant directories of all component instances under that realm.
Structure of the hub
A hub has the following filesystem layout:
hub
├── children
| ├── foo
| | └── ...
| └── bar
| └── ...
├── exposed
├── ns
├── out
└── runtime
When a component instance is resolved, the following directories are present in its hub:
children: Hub directories of the children of this component instance.exposed: Capabilities exposed by this component instance in its manifest.ns: Capabilities used by this component instance in its manifest.
When a component instance is running, the following directories are also present:
out: Capabilities served by the program of this component instance.runtime: Debug information served by the runner of this component instance.
Accessing the root hub
A hub scoped to the root component is available in the serial shell and fx shell under the
directory /hub-v2.
(host)$ fx shell
$ cd hub-v2
$ ls
children
exposed
ns
Example: List all capabilities exposed by a component
To list all capabilities exposed by the component with moniker /bootstrap/archivist, do the
following:
(host)$ fx shell
$ cd /hub-v2/children/bootstrap/children/archivist/exposed
$ ls
diagnostics
fuchsia.diagnostics.ArchiveAccessor
fuchsia.diagnostics.FeedbackArchiveAccessor
fuchsia.diagnostics.LegacyMetricsArchiveAccessor
fuchsia.diagnostics.LoWPANArchiveAccessor
fuchsia.diagnostics.LogSettings
fuchsia.logger.Log
fuchsia.logger.LogSink
Example: See the namespace of a component
To see the namespace of the component with moniker /core/memory_monitor, do the following:
(host)$ fx shell
$ cd /hub-v2/children/core/children/memory_monitor/ns
$ ls
cache
config
dev
pkg
svc