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image

Usage​

rc image build --stack python
rc image build --stack python --stack go
rc image build --stack python,go
rc image build --all
FlagDescription
--stackcatalog language; repeatable or comma-separated
--allevery language in the catalog

Without --stack or --all, the command fails with informe --stack ou --all. A language outside the catalog fails with E006.

Through the Taskfile (which compiles first):

task image:build -- --stack python
task image:build -- --all

image prune​

rc image prune          # old builds no name points to anymore (the guest or start.sh changed, the key changed)
rc image prune --all    # also the images and packs no machine uses

Images outside the catalog (rc machine create --image ...) use the same build, without warmup.

Output​

One line per language:

python <caminho do ext4> cached=false elapsed=<tempo> <métricas do build>
  • cached=true when the key already existed in the cache and nothing was rebuilt.
  • The metrics come from the build VM: extraction, warmup and mkfs times, plus the used size and the disk size.

What the build does​

  1. Pulls the OCI image with go-containerregistry (no Docker) and flattens the layers into a tar.
  2. Boots an Alpine 3.22.6 build VM (the official Alpine base tarball, with its sha256 checked; e2fsprogs and GNU tar via apk).
  3. Inside it, as root: extracts the tar into a tmpfs, injects the guest and start.sh into /opt/runner/, runs the warmup in a chroot and generates the ext4 with mkfs.ext4 -d.
  4. Writes <lang>-<chave>.ext4 to the cache and points the <lang>.ext4 symlink at it.

The reason for each step, the cache key and each language's warmup are in Images.

When to rebuild​

The key includes the image digest, the warmup, build.sh, start.sh and the guest. After changing any of them — including recompiling the guest with different code — run the build again: the key changes on its own and a new image is generated.

Timing​

On the measured machine (macOS 27.0.1, Apple Silicon), the Python image took ~8–10 s, 2.7 s of which were pull and flattening. The Go one took 35 s, 28 of them in mkfs.ext4. The build needs network (pull and warmup); the job VM has none.