ffx component explore

ffx component explore is an experimental ffx plugin that allows you to interactively explore the internals of fuchsia components. Unlike fx shell, you only get access to your component's incoming & outgoing capabilities. This means you're able to explore in an environment almost identical to what your component sees.

Currently, it launches a Dash process scoped to your component. In this process:

  • You have a similar command-line experience to fx shell.
  • You can use familiar tools such as ls, cat and grep.
  • You can explore your component's incoming and outgoing capabilities.

Getting started

  1. Ensure your branch is synced to tip-of-tree with jiri update.

  2. Ensure that you are building an engineering product like core, terminal or workstation_eng.

  3. Start up an emulator and/or connect to a device.

  4. Choose a component moniker and start exploring:

    > ffx component explore /bootstrap/archivist
    $ ls

    See what is the namespace root for more details on these directories.

How do I...

For the following sections, we use the /bootstrap/archivist moniker. This should be replaced with the moniker of your component.

Explore the capabilities available to my component?

The /ns directory contains the component's namespace, exactly as your component would see it.

> ffx component explore /bootstrap/archivist
$ cd ns
$ ls
$ cd data
$ ls
$ mv logs.txt logs2.txt
$ mkdir captures

Explore the capabilities exposed by my component?

The /exposed directory contains the capabilities exposed from your component to its parent.

> ffx component explore /bootstrap/archivist
$ cd exposed
$ ls

Explore the capabilities my component is serving?

If a component is running, the /out directory contains all the capabilities currently served by it.

> ffx component explore /bootstrap/archivist
$ cd out
$ ls
$ cd svc
$ ls

Explore debug runtime data about my component?

If your component is running, the /runtime directory contains debug information provided by the component runner.

> ffx component explore /bootstrap/archivist
$ cd runtime/elf
$ ls
$ cat process_id

Run a command-line tool I built for my component?

This isn't supported yet, but we're working on it. Soon, we will add support for running custom command-line tools that can use your component's incoming/exposed capabilities.

This is great because:

  • Current models for running tools on device are deprecated or provide too much privilege.
    • The ongoing deprecation of .cmx components means that we will no longer have support for CMX shell tools.
    • Raw binaries run in fx shell have access to more capabilities than they need.
  • Tools do not need to know the component topology to access capabilities.
    • ffx component explore provides a predictable directory structure that isn't tied to the component's moniker.
  • Tools often need capabilities exposed by the component they are built for.
    • net uses fuchsia.net.* capabilities exposed by the netstack component.
    • activity-ctl uses fuchsia.activity.* capabilities exposed by the activity component.
    • stash-ctl uses fuchsia.stash.* capabilities exposed by the stash component.


What is Dash?

Dash is the command interpreter used in fx shell, serial console, terminal windows, virtcon, etc. We are using it as the experience for ffx component explore because it is familiar and serves as a good starting point for cd-ing and ls-ing around to explore your component.

Why can't I see child components from the parent?

We do not allow accessing child components directly from the parent. Using knowledge of the component topology to access a child component's capabilities made tools brittle in fx shell. Tools used to keep hard-coded paths to /hub-v2 which encoded knowledge about the system topology.

As an alternative, we recommend:

  • explicitly routing capabilities from the child to the parent component.
  • exploring the child component itself.

How is this different from ffx component run?

ffx component run launches a component in a preset collection (ffx-laboratory) and offers no interactive capabilities. ffx component explore allows exploring any existing component in the topology interactively.

What is the namespace root (/) in ffx component explore?

ffx component explore creates a virtual file system at the namespace root that contains the following directories:

Directory Description
/bin contains a standard set of tools such as ls, cat, mkdir etc.
/exposed contains all exposed capabilities.
/ns contains the component's namespace, exactly as your component would see it.
/svc contains capabilities needed by Dash.

If your component is running, the following directories are also present:

Directory Description
/out contains all capabilities currently being served by the component.
/runtime contains debug information served by the component’s runner.

Can I access Zircon handles or make FIDL calls via the Dash shell?

That is not supported directly from the command interpreter.

How do I file a feature request for $NEW_FEATURE?

File all feature requests under the ComponentFramework > Tools monorail component