Sync host opencode auth into guest work disks

Refresh guest opencode auth from the host at VM start so guest opencode can reuse the local login without baking secrets into managed images.

Reuse the existing work-disk preparation path to copy ~/.local/share/opencode/auth.json into /root/.local/share/opencode/auth.json with mode 0600, and warn and skip when the host file is missing or unreadable so any existing guest auth stays in place.

Add daemon coverage for copy, replacement, and warn-and-skip cases, document the restart behavior in the README, and validate with go test ./... plus make build. Existing VMs pick the new auth up on their next restart.

2026-03-21 22:36:13 -03:00

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banger

banger manages Firecracker development VMs with a local daemon, managed image artifacts, and a localhost web UI.

Requirements

Linux with /dev/kvm
sudo
Firecracker installed on PATH, or firecracker_bin set in config
The usual host tools checked by ./build/bin/banger doctor

banger now owns complete managed image sets. A managed image includes:

rootfs
optional work-seed
kernel
optional initrd
optional modules

There is no runtime bundle anymore.

Build

make build

This writes:

./build/bin/banger
./build/bin/bangerd
./build/bin/banger-vsock-agent

Install

make install

That installs:

banger
bangerd
the banger-vsock-agent companion helper under ../lib/banger/

Config

Config lives at ~/.config/banger/config.toml.

Supported keys:

log_level
web_listen_addr
firecracker_bin
ssh_key_path
default_image_name
auto_stop_stale_after
stats_poll_interval
metrics_poll_interval
bridge_name
bridge_ip
cidr
tap_pool_size
default_dns

If ssh_key_path is unset, banger creates and uses:

~/.config/banger/ssh/id_ed25519

default_image_name now only means “use this registered image when vm create omits --image”. The daemon does not auto-register images from host paths.

Core Workflow

Check the host:

./build/bin/banger doctor

./build/bin/banger image register \
  --name base \
  --rootfs /abs/path/rootfs.ext4 \
  --kernel /abs/path/vmlinux \
  --initrd /abs/path/initrd.img \
  --modules /abs/path/modules

Build a managed image from an existing registered image:

./build/bin/banger image build \
  --name devbox \
  --from-image base \
  --docker

Promote an unmanaged image into daemon-owned managed artifacts:

./build/bin/banger image promote base

Create and use a VM:

./build/bin/banger vm create --image devbox --name testbox
./build/bin/banger vm ssh testbox
./build/bin/banger vm stop testbox

vm create stays synchronous by default, but on a TTY it now shows live progress until the VM is fully ready.

Web UI

bangerd serves a local web UI by default at:

http://127.0.0.1:7777

See the effective URL with:

./build/bin/banger daemon status

Disable it with:

web_listen_addr = ""

Guest Services

Provisioned images include:

banger-vsock-agent
guest networking bootstrap
mise
opencode
a default guest opencode service on 0.0.0.0:4096

If host ~/.local/share/opencode/auth.json exists, banger syncs it into the guest at /root/.local/share/opencode/auth.json on VM start. Changes on the host take effect after the VM is restarted.

From the host:

./build/bin/banger vm ports testbox
opencode attach http://<guest-ip>:4096

Manual Helpers

The shell helpers are now explicit manual workflows under ./build/manual.

Rebuild a Debian-style manual rootfs:

make rootfs ARGS='--base-rootfs /abs/path/rootfs.ext4 --kernel /abs/path/vmlinux --initrd /abs/path/initrd.img --modules /abs/path/modules'

The output lands in:

./build/manual/rootfs-docker.ext4
./build/manual/rootfs-docker.work-seed.ext4

Experimental Void Flow

Stage a Void kernel:

make void-kernel

Build the experimental Void rootfs:

make rootfs-void

make void-register

That flow uses:

./build/manual/void-kernel/
./build/manual/rootfs-void.ext4
./build/manual/rootfs-void.work-seed.ext4

Experimental Alpine Flow

Stage an Alpine virt kernel:

make alpine-kernel

Build the experimental Alpine rootfs:

make rootfs-alpine

make alpine-register

Create a VM from it:

./build/bin/banger vm create --image alpine --name alpine-dev