Skip to main content
meta-nerveshub is a Yocto layer that packages the Linux agent into an image. The layer is only the agent — meta-rauc does the bundle and slot work.

​
Layers it depends on

Both are declared in LAYERDEPENDS, so a missing one fails when the layer is added rather than deep into a build. meta-rauc supplies the rauc the agent shells out to. The agent talks to rauc install over D-Bus, so the image needs rauc and its service running. meta-rust-bin supplies the toolchain. The agent needs Rust 1.85 — where edition 2024 was stabilised — and no released Yocto ships one that new: scarthgap has cargo 1.75, walnascar 1.84. meta-rust-bin packages prebuilt upstream toolchains and spans kirkstone through wrynose, so the Rust version stops being a function of the Yocto release. The recipe inherits cargo_bin from that layer rather than poky’s cargo.
That tradeoff is worth knowing before you adopt it. In meta-rust-bin’s own words, prebuilt toolchains “will never be able to support architectures or options not supported by the Rust team itself”, and the prebuilt standard library may be less efficient than a custom-compiled one. They are also upstream binaries rather than something your build system compiled, which matters if you have reproducibility or audit requirements.

​
Required DISTRO_FEATURES

Both rauc and systemd have to be present:
rauc is meta-rauc’s requirement rather than this layer’s; without it meta-rauc warns and the image has no RAUC support to speak of.
Without systemd, systemd_system_unitdir expands to nothing and the unit installs nowhere — the package builds, ships a binary with nothing to start it, and says nothing. The recipe guards the install so that is a missing unit rather than a broken one, but the image still needs systemd for the agent to run as intended.

​
Updating the crate list

Yocto fetches offline, so every crate is declared as a source rather than resolved by cargo during do_compile. After a Cargo.lock change:
That rewrites nerves-hub-link-agent-crates.inc.

​
Configuring the agent

Packaging puts the binary and its unit in the image; it does not configure it. See Linux Agent for the TOML config, and the agent’s docs/deploying.md for the service user, the device identifier and the rest of the deployment contract.