ffx component explore

ffx component explore is an ffx plugin that allows you to interactively explore the internals of fuchsia components. Unlike fx shell, the namespace only contains your component's incoming & outgoing capabilities. This restriction 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
    exposed
    ns
    out
    runtime
    svc
    

    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
pkg
data
svc
$ cd data
$ ls
logs.txt
$ mv logs.txt logs2.txt
$ mkdir captures

If you want the shell namespace to match the component namespace, use the -l/--layout flag.

> ffx component explore /bootstrap/archvisit -l namespace
$ ls
pkg
data
svc

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
fuchsia.foo.bar.MyProtocol

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
diagnostics
svc
$ cd svc
$ ls
fuchsia.foo.bar.MyProtocol

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
args
process_id
job_id
$ cat process_id
7352

Run a command non-interactively?

Use the -c/--command flag to run a command in the shell non-interactively and receive its stdout, stderr and exit code.

> ffx component explore /bootstrap/archivist -c "cat /runtime/elf/process_id"
2542

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 namespace capabilities.

FAQ

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 creates and then starts a component in a specified collection within the component topology. It offers no interactive capabilities. ffx component explore allows exploring any existing component in the topology interactively. You can use ffx component explore to learn about a component you just created using ffx component run.

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

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

Directory Description
/.dash contains binaries needed by Dash.
/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.

If the --layout namespace flag is set, then the shell's namespace will match the component's namespace.

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