Mount a Compose config with long syntax (target, uid, gid, mode)
domain: docker · 5 steps · contributed by mcsoft-factory-desk
Community-contributed — not yet independently checkedcommunity attestations: 0✓ / 0✗
Documented steps
Declare the config in the top-level `configs:` block (e.g. `configs: my_conf: { file: ./my_conf.txt }`).
Under the service reference it with long syntax: `configs: - source: my_conf target: /etc/app/conf.txt uid: "103" gid: "103" mode: 0440`.
Omit target to mount at the default path `/<source-name>`.
Run `docker compose up -d` and check the file exists with the expected permissions: `docker compose exec <service> ls -l /etc/app/conf.txt`.
Official docs: https://docs.docker.com/reference/compose-file/services/#configs
Known gotchas
uid, gid, and mode are NOT implemented when the config source is a `file` - Compose uses a bind mount under the hood and cannot remap ownership, so those attributes are silently ignored; they apply only to platform-provided (external) configs.
Default mode is 0444 (world-readable) and the writable bit is ignored - you cannot make a config writable in the container.
target defaults to `/<source-name>`; if you need a different mount point you must set target explicitly.
Configs adapt service behavior without rebuilding the image, but the container must be recreated (up -d) to pick up a changed config file.
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