Add build-firmware skill: native ESP-IDF build, no Docker needed

CI builds firmware inside the espressif/idf Docker image, but this
sandbox can't run containers at all -- it strips cap_sys_admin (and
blocks unshare) from the capability set even for root, which container
image-layer extraction and namespace setup both need. Confirmed by
hand: docker.io installs and dockerd starts fine, but even a bare
`docker run hello-world` fails to extract its own layer.

Works around it by installing ESP-IDF natively instead (git clone +
its own install.sh, scoped to just this project's esp32c6 target) --
the same way a developer would set it up on their own machine, needing
nothing this sandbox disallows. Verified end-to-end: both board
variants (devkit, xiao) build clean from a fresh checkout via the
packaged setup.sh/build.sh.
This commit is contained in:
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---
name: build-firmware
description: Compile the espresso_frame ESP32-C6 firmware (firmware/) for both board variants without Docker -- a native, non-container ESP-IDF v6.0 install. Use when asked to build the firmware, verify a firmware/main/*.c change actually compiles, or check both the devkit and xiao board targets.
---
Compiles `firmware/` (ESP-IDF, targeting ESP32-C6) locally, without
Docker -- CI's `firmware-build-check.yml`/`firmware-release-build.yml`
build inside the `espressif/idf:release-v6.0` container image, but
**this sandbox cannot run containers at all**: `docker.io` installs and
`dockerd` starts fine even as root, but the sandbox strips
`cap_sys_admin` (and blocks the bare `unshare` syscall) from the
capability set regardless of uid, which container image-layer
extraction and namespace setup both require. Confirmed by hand:
`docker run hello-world` fails to extract even the tiny hello-world
layer ("failed to extract layer... operation not permitted" with the
overlayfs snapshotter; "unshare: operation not permitted" even with
the vfs storage driver instead). This is a hard restriction of the
sandbox itself, not a permissions/setup problem -- don't spend time
re-trying `--privileged`-equivalent flags or alternate storage drivers,
none of it routes around a missing `cap_sys_admin`.
The workaround: skip containers entirely and install ESP-IDF the same
way a developer would set it up on their own machine (`git clone` +
ESP-IDF's own `install.sh`) -- that path needs nothing this sandbox
disallows, just normal file/process operations.
## Setup (once per fresh container)
```bash
bash .claude/skills/build-firmware/setup.sh
```
Installs (via real `apt-get` -- this container actually has root and a
working package manager, unlike run-server's Chromium bootstrap which
had neither):
- OS build deps: `python3`/`venv`/`pip`, `cmake`, `ninja-build`,
`flex`/`bison`/`gperf`, `build-essential`, `libusb-1.0-0`.
- ESP-IDF itself: a shallow, single-branch, recursive-submodule clone
of `release/v6.0` (~700MB) into `~/.espressif-idf/esp-idf` -- matches
the IDF version CI's Docker image pins. Only clones once; re-running
`setup.sh` never touches an existing checkout.
- The esp32c6 toolchain + Python venv, via ESP-IDF's own
`./install.sh esp32c6` -- scoped to just this project's one target
(see `firmware/README.md`'s board table), not every chip ESP-IDF
supports, to keep the download/disk footprint down. `install.sh` is
already idempotent on its own, so `setup.sh` always calls it rather
than duplicating that check -- a re-run costs a few seconds once
everything's cached.
Takes a few minutes on a cold run (mostly `install.sh`'s own pip/tool
downloads), well under a minute on a re-run. Needs real root (`apt-get
install`) -- if this container ever runs as non-root, this setup
doesn't apply as-is (would need the same non-root apt-download +
`dpkg-deb -x` extraction dance `run-server`'s `setup.sh` uses for
Chromium).
Disk: budget ~4GB free before starting (esp-idf checkout + toolchain +
Python env land around 3.4GB in `~/.espressif`, plus the ~700MB
checkout itself). Confirmed working with as little as ~7GB free.
## Build
```bash
bash .claude/skills/build-firmware/build.sh # devkit (default)
bash .claude/skills/build-firmware/build.sh xiao
bash .claude/skills/build-firmware/build.sh both # both variants
```
Each board gets its own build directory and generated sdkconfig (see
`firmware/build_for_board.sh`'s own comment) -- building one never
disturbs the other. `build.sh` auto-runs `set-target esp32c6` the very
first time a board is built (no generated sdkconfig yet); later builds
skip straight to `idf.py build`. Extra arguments pass straight through
to `idf.py`, e.g.:
```bash
bash .claude/skills/build-firmware/build.sh xiao flash -p /dev/ttyUSB0
```
`flash`/`monitor` need an actual attached device and serial port --
this sandbox has neither, so those only work when this skill runs
somewhere hardware is actually plugged in (a real dev machine, or a
differently-configured environment with device passthrough).
A clean build of one board takes ~30s once the target's already been
configured (~1,000 build steps total split across both boards, most of
it ESP-IDF's own components -- this project's own `firmware/main/*.c`
and `firmware/components/*` sources are a small fraction of that and
compile in a few seconds). Output lands at
`firmware/build/espresso_frame.bin` (devkit) or
`firmware/build_xiao/espresso_frame.bin` (xiao) -- both paths are
gitignored (`firmware/.gitignore`... actually the repo root
`.gitignore`'s "ESP-IDF firmware build output" section), so nothing
here needs cleaning up before a commit.
## Verified
Both board variants (`devkit` set-target esp32c6 + build, `xiao`
set-target esp32c6 + build) built successfully end-to-end using this
exact setup.sh/build.sh pair, producing real
`espresso_frame.bin` images with normal free-space margins (41%/36%
of their respective app partitions) and no errors -- only one
pre-existing, unrelated warning (`battery.c`'s unused `TAG` when that
file's logging is compiled out). This is a real compile check, not
just a syntax read -- if a future change breaks the build, this skill
will actually catch it.
## Troubleshooting
- **`docker: ... unshare: operation not permitted` / `failed to
extract layer ... operation not permitted`**: expected in this
sandbox, see the top of this file. Don't debug it further -- use this
skill's native install instead.
- **`ESP-IDF not found at ... -- run setup.sh first`**: `build.sh`'s
own check for a missing `$IDF_DIR/export.sh` -- run `setup.sh` (see
above) before the first build.
- **`idf.py: command not found` if you try to run it directly**: same
gotcha `firmware/build_for_board.sh` already documents -- `idf.py` is
normally a shell *function* from ESP-IDF's `export.sh`, not on PATH
as a real executable, so it isn't inherited into a script's own
subshell even after sourcing `export.sh` in your interactive shell
first. Use `build.sh` (or `build_for_board.sh`, which calls
`python "$IDF_PATH/tools/idf.py"` directly) instead of typing
`idf.py` in a fresh script/subshell.
- **Disk pressure during `install.sh`**: this environment runs close to
full (single-digit GB free is normal, not a sign of a leak) --
`df -h /` before running `setup.sh` if a build mysteriously fails
partway with a "no space left on device"-shaped error.
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#!/usr/bin/env bash
# Builds (or flashes/monitors, if a serial port is actually attached)
# the espresso_frame firmware for one board variant, via the project's
# own firmware/build_for_board.sh -- this script just sources the
# ESP-IDF environment first and auto-runs `set-target esp32c6` on a
# board's very first build (a fresh clone has no generated sdkconfig
# yet, same reasoning as CI's own build steps -- see firmware/README.md's
# "Building for the Seeed XIAO ESP32-C6" section).
#
# Usage:
# build.sh # build devkit (default)
# build.sh devkit
# build.sh xiao
# build.sh both # build both board variants
# build.sh xiao flash -p /dev/ttyUSB0 # only meaningful with real hardware attached
set -euo pipefail
script_dir="$(cd "$(dirname "${BASH_SOURCE[0]}")" && pwd)"
firmware_dir="$(git -C "$script_dir" rev-parse --show-toplevel)/firmware"
IDF_DIR="$HOME/.espressif-idf/esp-idf"
if [ ! -f "$IDF_DIR/export.sh" ]; then
echo "ESP-IDF not found at $IDF_DIR -- run setup.sh first" >&2
exit 1
fi
# export.sh is chatty and assumes an interactive shell prompt in spots;
# redirect its own stdout, not ours, so build.sh's actual output (and a
# real failure's stderr) stays visible.
source "$IDF_DIR/export.sh" > /dev/null
cd "$firmware_dir"
build_one() {
local board="$1"
shift
local sdkconfig
case "$board" in
devkit) sdkconfig="sdkconfig" ;;
xiao) sdkconfig="sdkconfig.xiao_local" ;;
*) echo "Unknown board '$board' -- expected 'devkit' or 'xiao'" >&2; exit 1 ;;
esac
if [ ! -f "$sdkconfig" ]; then
echo "==> $board: no generated sdkconfig yet, setting target esp32c6"
./build_for_board.sh "$board" set-target esp32c6
fi
local args=("$@")
if [ ${#args[@]} -eq 0 ]; then
args=(build)
fi
./build_for_board.sh "$board" "${args[@]}"
}
board="${1:-devkit}"
shift || true
if [ "$board" = "both" ]; then
build_one devkit "$@"
build_one xiao "$@"
else
build_one "$board" "$@"
fi
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#!/usr/bin/env bash
# One-time (idempotent) environment bootstrap for compiling the
# espresso_frame firmware (firmware/) without Docker -- see this
# skill's SKILL.md for why not Docker, even though that's what CI uses.
# Re-run any time; every step is safe/fast to repeat once already done.
set -euo pipefail
IDF_ROOT="$HOME/.espressif-idf"
IDF_DIR="$IDF_ROOT/esp-idf"
# Matches the espressif/idf:release-v6.0 image CI's
# firmware-build-check.yml/firmware-release-build.yml use -- keep this
# in sync with those workflow files if the project's pinned IDF version
# ever changes.
IDF_BRANCH="release/v6.0"
# 1. OS packages ESP-IDF's own install.sh needs (python3 + venv/pip,
# cmake, ninja, a C toolchain for the odd host-side code generator, git
# for the clone below, flex/bison/gperf for mbedtls/etc.'s generated
# parsers, libusb for esptool's USB/JTAG bits even though this skill
# doesn't flash real hardware). Installed via apt with real root --
# unlike run-server's Chromium bootstrap, this container actually has
# root and a working apt, so no non-root extraction dance is needed
# here.
PKGS="git python3 python3-venv python3-pip cmake ninja-build ccache libusb-1.0-0 wget flex bison gperf build-essential"
missing=()
for pkg in $PKGS; do
dpkg -s "$pkg" >/dev/null 2>&1 || missing+=("$pkg")
done
if [ ${#missing[@]} -gt 0 ]; then
echo "installing OS packages: ${missing[*]}"
apt-get update
DEBIAN_FRONTEND=noninteractive apt-get install -y "${missing[@]}"
fi
# 2. ESP-IDF checkout -- shallow, single branch, recursive submodules
# also shallow (~700MB total, vs. several GB for a full clone). Only
# clones once; re-running this script never re-clones or resets it, so
# any local changes you made for debugging survive a re-run.
if [ ! -d "$IDF_DIR/.git" ]; then
echo "cloning esp-idf $IDF_BRANCH into $IDF_DIR ..."
mkdir -p "$IDF_ROOT"
git clone --branch "$IDF_BRANCH" --depth 1 --shallow-submodules --recursive \
https://github.com/espressif/esp-idf.git "$IDF_DIR"
else
echo "esp-idf already cloned at $IDF_DIR"
fi
# 3. Toolchain + Python virtualenv, scoped to esp32c6 only -- this
# project's one target (see firmware/README.md's board table). Scoping
# avoids downloading toolchains for every chip ESP-IDF supports, which
# matters given this container's disk headroom. install.sh is already
# idempotent on its own (checks what's present and skips it), so this
# always calls it rather than trying to duplicate that check here --
# a re-run only costs a few seconds once everything's cached.
echo "running esp-idf install.sh esp32c6 (fast if already installed) ..."
(cd "$IDF_DIR" && ./install.sh esp32c6)
echo "setup complete -> $IDF_DIR/export.sh (build.sh sources this for you)"