管理クラスタにある すべての CAPI Cluster の kubeconfig を、手元の kubeconfig にマージする

スクリプト

#!/usr/bin/env bash
set -euo pipefail

# 管理クラスタ上の全 Cluster API Cluster の kubeconfig を取得し、
# 現在使用中の kubeconfig に直接マージする。

need() { command -v "$1" >/dev/null 2>&1 || { echo "[error] '$1' not found"; exit 1; }; }
need kubectl
need clusterctl

# 既存 kubeconfig の決定
if [[ -n "${KUBECONFIG:-}" ]]; then
  TARGET="${KUBECONFIG%%:*}"  # 複数指定時は先頭を採用
  ORIG_ENV="$KUBECONFIG"
else
  mkdir -p "${HOME}/.kube"
  TARGET="${HOME}/.kube/config"
  ORIG_ENV="$TARGET"
fi

TMPDIR="$(mktemp -d)"
trap 'rm -rf "$TMPDIR"' EXIT
LIST="$TMPDIR/cluster-list.txt"
GENS=""

echo "[info] Listing Cluster API clusters on the management cluster..."
kubectl get clusters -A -o jsonpath='{range .items[*]}{.metadata.namespace}{"\t"}{.metadata.name}{"\n"}{end}' > "$LIST" || true

if [[ ! -s "$LIST" ]]; then
  echo "[warn] No Cluster API clusters found. Nothing to merge."
  exit 0
fi

# 1クラスタずつ取得 & コンテキスト名を "<ns>/<ctx>" にして衝突回避
while IFS=$'\t' read -r ns name; do
  [[ -z "${ns:-}" || -z "${name:-}" ]] && continue
  f="$TMPDIR/${ns}-${name}.kubeconfig"
  echo "[info] Fetching kubeconfig for ${ns}/${name} ..."
  clusterctl get kubeconfig "$name" --namespace "$ns" > "$f"

  for ctx in $(kubectl --kubeconfig "$f" config get-contexts -o name || true); do
    new_ctx="${ns}/${ctx}"
    if [[ "$ctx" != "$new_ctx" ]]; then
      kubectl --kubeconfig "$f" config rename-context "$ctx" "$new_ctx" >/dev/null || true
    fi
  done

  [[ -z "$GENS" ]] && GENS="$f" || GENS="$GENS:$f"
done < "$LIST"

# 既存 kubeconfig のバックアップ
ts="$(date +%Y%m%d%H%M%S)"
if [[ -f "$TARGET" ]]; then
  cp -p "$TARGET" "${TARGET}.bak-${ts}"
  echo "[info] Backup created: ${TARGET}.bak-${ts}"
else
  : > "$TARGET"
fi

# 既存 + 生成をまとめて flatten して上書き
ALL_SOURCES="${ORIG_ENV}:${GENS}"
ALL_SOURCES="${ALL_SOURCES#:}"; ALL_SOURCES="${ALL_SOURCES%:}"

echo "[info] Merging into: $TARGET"
KUBECONFIG="$ALL_SOURCES" kubectl config view --flatten > "${TARGET}.tmp"
chmod 600 "${TARGET}.tmp"
mv -f "${TARGET}.tmp" "$TARGET"

echo "[done] Merged kubeconfig written to: $TARGET"
kubectl --kubeconfig "$TARGET" config get-contexts -o name || true

chmod +x ./merge-capi-kubeconfigs.sh
./merge-capi-kubeconfigs.sh