- In Alpine Linux containers (commonly used as Docker base images),
standard DNS resolution is provided by **musl**, a lightweight C
standard library (libc). Musl implements DNS lookups via
`getaddrinfo()`, which queries AAAA (IPv6) records first.
- Problem: DNS did not work correctly **inside containers**. Any
system command attempting to resolve hostnames
(e.g., `ping dynamodb-admin`) **failed** when the DNS server
responded NXDOMAIN for AAAA records, even if A (IPv4) records
existed. Explicitly forcing IPv4 (`ping -4dynamodb-admin`) worked
correctly, showing the issue is specific to musl’s IPv6-first behavior.
- Consequence: In IPv4-only environments, Alpine-based containers
cannot resolve hostnames using standard tools or libraries.
Applications relying on `getaddrinfo()` fail with ENOTFOUND,
breaking networking and inter-container communication.
- Root cause: Following RFC 8305 / RFC 6724, musl treats NXDOMAIN
for AAAA as “hostname does not exist” and does not fallback to A
(IPv4) records.
- Fix: The Apple Container DNS engine now behaves as follows:
* If an **A record exists**, AAAA queries return **NOERROR with empty
answer (NODATA)**.
* If neither **A nor AAAA** exist, NXDOMAIN is returned.
This ensures that Alpine-based containers in IPv4-only networks can
correctly resolve hostnames inside containers without modifying
container images or application code.
- Closes#508.
## Type of Change
- [ ] Bug fix
- [x] New feature
- [ ] Breaking change
- [ ] Documentation update
## Motivation and Context
Adds a `container volume prune` command that removes volumes with no
container references and reports the amount of disk space reclaimed.
This helps users clean up unused volumes and easily reclaim disk space.
Also updates the `volume delete` documentation to clarify and highlight
how the `--all` flag works.
## Testing
- [x] Tested locally
- [x] Added/updated tests
- [x] Added/updated docs
- Closes#615.
Improves project organization. Separates service so it can be tested and
used separately from the executable target. No functional changes.
Rado Kubiak | Rado x Tech