# Nic Docker Images

> Nic Docker Images is an Agent Skill for devops & security published in the nginx/kubernetes-ingress repository on GitHub: a SKILL.md instruction file an AI agent can load to do this task.

Docker image build system, Dockerfile structure, image variants, build scripts, and Makefile targets for NIC. Use when building container images, modifying the Dockerfile, adding new image variants, debugging image builds, or working with build scripts.

- Skill name: `nic-docker-images`
- Category: [DevOps & Security](https://www.openparable.com/skill/devops-security/1)
- Source: https://github.com/nginx/kubernetes-ingress/blob/HEAD/.github/skills/nic-docker-images/SKILL.md
- Repository: nginx/kubernetes-ingress (5,049 GitHub stars when collected)

## SKILL.md

# NIC Docker Image Build System

## Dockerfile Architecture

Single `build/Dockerfile` (~850 lines), heavily multi-stage. The `BUILD_OS` arg selects which base image stage is used.

```text
nginx-files (scratch)           <- Collects repo files, signing keys, scripts
  |
OS-specific base stages         <- One per variant (debian, alpine, ubi, *-plus, *-nap)
  |
FROM ${BUILD_OS} AS common      <- Runs common.sh + patch-os.sh, sets permissions
  |
TARGET stages (final image)     <- local, container, goreleaser, debug, download, aws, patched
```

---

## Image Variants

3 OS families x 2 NGINX editions x optional NAP = ~20 variants.

| OS | OSS | Plus | Plus+WAF | Plus+WAFv5 | Plus+DoS | Plus+WAF+DoS | Plus+FIPS | Plus+WAF+FIPS | Plus+WAFv5+FIPS |
| --- | --- | --- | --- | --- | --- | --- | --- | --- | --- |
| Debian | yes | yes | yes | yes | yes | yes | - | - | - |
| Alpine | yes | yes | - | - | - | - | yes | yes | yes |
| UBI 10 | yes | yes | yes | yes | yes | yes | - | - | - |

**Architecture**: `amd64` + `arm64` for OSS and Plus. NAP variants are `amd64` only.

---

## Makefile Image Targets

All targets call `docker build --platform linux/$(ARCH) --target $(TARGET) -f build/Dockerfile`.

| Target | BUILD_OS | NAP_MODULES |
| --- | --- | --- |
| `debian-image` | `debian` | - |
| `alpine-image` | `alpine` | - |
| `ubi-image` | `ubi` | - |
| `debian-image-plus` | `debian-plus` | - |
| `alpine-image-plus` | `alpine-plus` | - |
| `alpine-image-plus-fips` | `alpine-plus-fips` | - |
| `alpine-image-nap-plus-fips` | `alpine-plus-nap-fips` | `waf` |
| `alpine-image-nap-v5-plus-fips` | `alpine-plus-nap-v5-fips` | `waf` |
| `ubi-image-plus` | `ubi-10-plus` | - |
| `debian-image-nap-plus` | `debian-plus-nap` | `waf` |
| `debian-image-nap-v5-plus` | `debian-plus-nap-v5` | `waf` |
| `debian-image-dos-plus` | `debian-plus-nap` | `dos` |
| `debian-image-nap-dos-plus` | `debian-plus-nap` | `waf,dos` |
| `ubi-image-nap-plus` | `ubi-10-plus-nap` | `waf` |
| `ubi-image-nap-v5-plus` | `ubi-10-plus-nap-v5` | `waf` |
| `ubi-image-dos-plus` | `ubi-10-plus-nap` | `dos` |
| `ubi-image-nap-dos-plus` | `ubi-10-plus-nap` | `waf,dos` |
| `all-images` | Builds 18 variants | - |
| `push` | `docker push` to `PREFIX:TAG` | - |
| `patch-os` | OS patches existing image | - |

Plus images receive `$(PLUS_ARGS)`: `--secret id=nginx-repo.crt --secret id=nginx-repo.key`.

### TARGET Variable

| Target | Use Case |
| --- | --- |
| `local` | Default -- binary pre-built on host, copied in |
| `container` | Binary built inside Docker (multi-arch capable) |
| `goreleaser` | Binary from GoReleaser `dist/` (CI builds) |
| `debug` | Includes delve debugger |
| `download` | Extracts binary from published Docker Hub image |
| `aws` | AWS marketplace variant |
| `patched` | OS patches an existing image |

---

## Key Build Args

| Arg | Purpose | Source of truth |
| --- | --- | --- |
| `BUILD_OS` | Base image stage | `Makefile` targets + Dockerfile stages |
| `IC_VERSION` | Ingress controller version | `.github/data/version.txt` |
| `NGINX_PLUS_VERSION` | NGINX Plus version | `build/Dockerfile` |
| `NGINX_OSS_VERSION` | NGINX OSS version | `build/Dockerfile` |
| `NAP_MODULES` | App Protect modules | Any of `waf`, `dos`, or `waf,dos` |
| `PREBUILT_BASE_IMG` | Base for prebuilt targets | GCR image ref (set by CI) |

Do not hard-code `IC_VERSION` or `NGINX_VERSION` values in this file or in other docs as they change every release. Always reference `.github/data/version.txt` or the Renovate-managed Dockerfile pin.

---

## Build Scripts (`build/scripts/`)

| Script | Purpose |
| --- | --- |
| `common.sh` | Sets up directories, copies NGINX templates (v1/v2), sets file permissions (101:0), runs `setcap` on nginx binaries |
| `agent.sh` | Configures nginx-agent ownership; creates NMS compiler symlinks for NAP v4 |
| `nap-waf.sh` | Creates WAF directories (`/etc/nginx/waf/nac-policies`, `/opt/app_protect/`) |
| `nap-dos.sh` | Creates DoS directories (`/root/app_protect_dos`, `/shared/cores`) |
| `ubi-setup.sh` | UBI-specific: installs shadow-utils, creates nginx user/group (101:0) |
| `ubi-clean.sh` | UBI-specific: removes build-time packages, cleans dnf cache |

---

## Key Conventions

- All images run as **UID 101** (nginx user), with `setcap cap_net_bind_service` for ports 80/443
- Docker BuildKit always enabled: uses `--mount=type=bind`, `--mount=type=secret`, `--mount=type=cache`
- Plus credentials use `--secret` mounts, **never** `COPY` into layers
- Fixed upstream base images use **pinned `@sha256:` digests** for reproducibility; some stages intentionally use build-arg/tag-selected bases (for example `BUILD_OS` or download/prebuilt images)
- All images include `nginx-module-otel` (OpenTelemetry) and `nginx-agent` (usage reporting)
- Plus images add `njs` and `fips-check` modules
- Renovate manages base image digests and tool versions via `# renovate:` comments

---

## Gotchas

- **Never** store Plus credentials in image layers -- always use `--secret` mounts
- **Never** add `arm64` to NAP image matrices -- NAP is `amd64` only
- **Always** use `BUILD_OS` to select variants, not separate Dockerfiles
- The `common` stage unifies all variants -- changes there affect every image
- `common.sh` detects Plus via `BUILD_OS` containing "plus" and creates OIDC directories
- `patch-os.sh` handles OS-level security updates at build time
- When adding new image dependencies, update the relevant OS-specific stage AND the common stage if needed

---

Source: https://www.openparable.com/skill/devops-security/nic-docker-images (OpenParable). Cite the canonical URL above.