How-to: sccache backend

sccache's backend is decoupled via an env file — set [cache] conf to a KEY=VAL file (mounted into containers as a secret). Without it, sccache uses a local cache volume.

Local S3 (garage)

docker run -d --name garage --restart always \
  -v $HOME/bupha-data/garage:/data \
  -v $HOME/bupha-data/garage.toml:/etc/garage.toml \
  -p 9100:9100 dxflrs/garage:v1.x.x

Then in the garage CLI: bucket create bupha-ci → key create sccache → bucket allow --read --write --owner bupha-ci --key sccache.

Env file:

SCCACHE_ENDPOINT=http://<docker-gateway>:9100
SCCACHE_BUCKET=bupha-ci
SCCACHE_REGION=garage
SCCACHE_S3_USE_SSL=false
AWS_ACCESS_KEY_ID=...
AWS_SECRET_ACCESS_KEY=...

Migrating to hosted S3 (R2 / AWS)

Same file, new values — SCCACHE_ENDPOINT to the provider URL, real region, new creds. No code changes; that's the point of the env file.