feat: ARM64 runner support and Slurm release line docs

CLAUDE.md

@@ -10,8 +10,9 @@ jobs. Personal, uncommitted instructions belong in `CLAUDE.local.md` (gitignored
   `-vvv` under `RUNNER_DEBUG`), run `sind doctor`, export `SIND_REALM` from the `realm`
   input, and create clusters (`scripts/create.sh`). Outputs: `clusters`, `version`.
 - `scripts/install.sh`: resolves `latest` from the redirect of the latest release page
-  (not the rate-limited API), enforces `MIN_VERSION`, downloads `sind-linux-amd64` into
-  `~/.local/bin`, and checks `sind version --json`.
+  (not the rate-limited API), enforces `MIN_VERSION`, downloads `sind-linux-amd64` (or
+  `sind-linux-arm64` on ARM64 runners, sind releases after v0.9.0) into `~/.local/bin`,
+  and checks `sind version --json`.
 - `scripts/create.sh`: each `clusters` entry is a config file path (scalar) or an inline
   config (map). It creates each cluster, prints its status, and writes the `clusters`
   output.

README.md

@@ -28,8 +28,10 @@ jobs:
 
 ## Requirements
 
-- A Linux x64 runner, such as `ubuntu-latest`. sind publishes no binaries for
-  other platforms.
+- A Linux x64 or ARM64 runner, such as `ubuntu-latest` or `ubuntu-24.04-arm`.
+  The action installs the sind binary for the runner's architecture. ARM64
+  runners need a sind release after v0.9.0, the first with linux/arm64
+  binaries and node images.
 - Docker and cgroup v2, which `sind doctor` checks before any cluster is
   created.
 - `bash`, `curl`, `jq` and [mikefarah `yq`](https://github.com/mikefarah/yq) v4.
@@ -106,6 +108,43 @@ jobs:
         if: always()
 ```
 
+## Slurm Versions
+
+Clusters use sind's default node image, `ghcr.io/gsi-hpc/sind-node:latest`, which
+carries the newest supported Slurm release line. sind also publishes an image per
+supported release line, tagged `<YY>.<MM>` (e.g. `25.11`). To pin a release line,
+or test against several, set the image in the cluster config:
+
+```yaml
+jobs:
+  test:
+    runs-on: ubuntu-latest
+    strategy:
+      matrix:
+        slurm: ['25.11', '26.05']
+    steps:
+      - uses: actions/checkout@v7
+
+      - uses: GSI-HPC/sind-action@v2
+        with:
+          clusters: |
+            - kind: Cluster
+              name: dev
+              defaults:
+                image: ghcr.io/gsi-hpc/sind-node:${{ matrix.slurm }}
+              nodes:
+                - controller
+                - worker: 2
+
+      - run: sind exec dev -- srun -N2 hostname
+
+      - uses: GSI-HPC/sind-action/cleanup@v2
+        if: always()
+```
+
+See [Official images](https://gsi-hpc.github.io/sind/container-images/building-images/#official-images)
+for the available tags.
+
 ## AI disclosure
 
 This project is developed with the help of AI coding tools. Since September 2026,

scripts/install.sh

@@ -1,11 +1,15 @@
 #!/usr/bin/env bash
 set -euo pipefail
 
-# sind releases only a Linux x86-64 binary.
-if [[ "$(uname -s)/$(uname -m)" != "Linux/x86_64" ]]; then
-  echo "::error::sind runs only on Linux x64 runners, not on $(uname -s) $(uname -m)"
-  exit 1
-fi
+# sind releases Linux binaries for x86-64 and, after v0.9.0, arm64.
+case "$(uname -s)/$(uname -m)" in
+  Linux/x86_64) ARCH=amd64 ;;
+  Linux/aarch64 | Linux/arm64) ARCH=arm64 ;;
+  *)
+    echo "::error::sind runs only on Linux x64 and ARM64 runners, not on $(uname -s) $(uname -m)"
+    exit 1
+    ;;
+esac
 
 REPO_URL="https://github.com/GSI-HPC/sind"
 VERSION="${SIND_VERSION:-latest}"
@@ -36,9 +40,16 @@ if [[ "$(printf '%s\n' "$MIN_VERSION" "$VERSION" | sort -V | head -n1)" != "$MIN
   exit 1
 fi
 
-echo "Installing sind ${VERSION}..."
+# v0.9.0 and earlier publish only sind-linux-amd64.
+LAST_AMD64_ONLY="v0.9.0"
+if [[ "$ARCH" == "arm64" && "$(printf '%s\n' "$LAST_AMD64_ONLY" "$VERSION" | sort -V | tail -n1)" == "$LAST_AMD64_ONLY" ]]; then
+  echo "::error::sind ${VERSION} has no linux/arm64 binary; ARM64 runners need a sind release after ${LAST_AMD64_ONLY}"
+  exit 1
+fi
+
+echo "Installing sind ${VERSION} (linux/${ARCH})..."
 
-DOWNLOAD_URL="${REPO_URL}/releases/download/${VERSION}/sind-linux-amd64"
+DOWNLOAD_URL="${REPO_URL}/releases/download/${VERSION}/sind-linux-${ARCH}"
 INSTALL_DIR="${HOME}/.local/bin"
 mkdir -p "$INSTALL_DIR"