Jason Stedwell
50 lines
2.0 KiB
Markdown
50 lines
2.0 KiB
Markdown
# ADR 0001 — Base Image Selection
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**Status:** Accepted
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---
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## Context
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The runner needs a base OS image that provides:
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- A working apt package ecosystem for installing `git`, `curl`, `jq`, `tini`, `ca-certificates`, `tzdata`.
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- Compatibility with Docker's official apt repository (for Docker CLI).
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- Compatibility with NodeSource (for Node.js 20 LTS).
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- A label environment the existing workflows reference: `ubuntu-latest`.
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Candidates considered:
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1. `ubuntu:22.04` — LTS, wide ecosystem support, good compatibility.
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2. `ubuntu:24.04` — Newer LTS, some tooling still stabilizing.
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3. `debian:bookworm-slim` — Smaller footprint, good compatibility, but `ubuntu-latest` label mismatch.
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4. `debian:bullseye-slim` — Older, stable, but further from `ubuntu-latest` expectations.
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---
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## Decision
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Use `ubuntu:22.04` as the base image, pinned by exact tag.
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---
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## Rationale
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- Existing Gitea workflows use `runs-on: ubuntu-latest`. Basing the runner image on Ubuntu 22.04 maximizes compatibility with GitHub Actions steps written for that environment.
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- Ubuntu 22.04 LTS has long-term support through 2027, reducing forced base image churn.
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- Docker's apt repository and NodeSource both officially support Ubuntu 22.04.
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- Ubuntu 22.04 is the most common self-hosted runner base image in community examples, so troubleshooting resources are abundant.
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---
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## Consequences
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- Final image size will be larger than a minimal Alpine or Debian slim base, which is acceptable given the goal of bundling all runtime dependencies.
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- When the workflow ecosystem moves to `ubuntu-24.04`, the base image can be bumped with a version argument change (`ARG UBUNTU_VERSION=24.04`).
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---
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## Alternatives considered
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**Debian bookworm-slim:** Smaller image, but the `ubuntu-latest` label in existing workflows creates an expectation of Ubuntu compatibility. Switching to Debian may cause subtle incompatibilities with actions that check the OS ID.
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**Ubuntu 24.04:** Not yet the default for `ubuntu-latest` as of the initial build date; 22.04 remains the more tested choice for self-hosted runners.
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