feat: add install_kubectl.sh ops script (#1319)

Author: rackerchris

scripts/install_kubectl.sh

@@ -0,0 +1,142 @@
+#!/bin/bash
+
+KUBECTL_DEST="/usr/local/bin/kubectl"
+ARCH=$(dpkg --print-architecture)
+DRY_RUN=false
+OWNER_UID="root" 
+OWNER_GID="root" 
+INSTALL_MODE="0755" 
+KUBE_VERSION_OVERRIDE=""
+
+# --- Argument Parsing ---
+if [[ "$1" =~ ^v?[0-9]+\.[0-9]+\.[0-9]+$ ]]; then
+    KUBE_VERSION_OVERRIDE="${1#v}"
+    shift
+fi
+
+if [[ "$1" == "--dry-run" ]] || [[ "$1" == "-n" ]]; then
+    DRY_RUN=true
+    echo "--- DRY-RUN MODE ACTIVATED ---"
+fi
+
+case "${ARCH}" in
+    "amd64")
+        KUBERNETES_ARCH="amd64"
+        ;;
+    "arm64")
+        KUBERNETES_ARCH="arm64"
+        ;;
+    *)
+        echo "Error: Unsupported architecture ${ARCH}. This script supports amd64 and arm64."
+        exit 1
+        ;;
+esac
+
+echo "Detected system architecture: ${KUBERNETES_ARCH}"
+
+get_kube_version() {
+    if ! command -v kubectl &> /dev/null; then
+        echo "Error: 'kubectl' command not found in PATH." >&2
+        return 1
+    fi
+
+    if $DRY_RUN && [ -z "${KUBE_VERSION_OVERRIDE}" ]; then
+        echo "1.28.5 (SIMULATED)"
+        return 0
+    fi
+    
+    SERVER_VERSION=$(kubectl version --client=false --output=json 2>/dev/null | jq -r '.serverVersion.gitVersion')
+
+    if [ -z "${SERVER_VERSION}" ] || [ "${SERVER_VERSION}" = "null" ]; then
+        echo "Error: Could not determine Kubernetes server version. Is KUBECONFIG set and is the cluster reachable?" >&2
+        return 1
+    fi
+
+    echo "${SERVER_VERSION#v}"
+}
+
+echo "Attempting to fetch Kubernetes server version..."
+
+if [ -n "${KUBE_VERSION_OVERRIDE}" ]; then
+    KUBE_VERSION="${KUBE_VERSION_OVERRIDE}"
+    echo "Target Kubernetes version OVERRIDDEN by argument: v${KUBE_VERSION}"
+else
+    KUBE_VERSION=$(get_kube_version)
+    
+    if [ $? -ne 0 ]; then
+        echo "FATAL: Auto-detection failed. When installing kubectl for the first time or when it's not in PATH, you MUST provide the target Kubernetes version as the first command-line argument (e.g., $0 1.29.1)." >&2
+        exit 1
+    fi
+    echo "Target Kubernetes version detected: v${KUBE_VERSION}"
+fi
+
+DOWNLOAD_URL="https://dl.k8s.io/release/v${KUBE_VERSION}/bin/linux/${KUBERNETES_ARCH}/kubectl"
+
+if $DRY_RUN; then
+    echo
+    echo "--- Dry-Run Actions to be performed ---"
+    
+    if [ -f "${KUBECTL_DEST}" ]; then
+        echo "DRY-RUN: Existing binary found. Permissions/Ownership would be read and preserved. File would be removed and replaced."
+    else
+        echo "DRY-RUN: No existing kubectl binary found. File would be installed using default permissions (${INSTALL_MODE}) and ownership (root:root)."
+    fi
+
+    echo "DRY-RUN: Binary v${KUBE_VERSION} would be downloaded from: ${DOWNLOAD_URL} to /tmp/kubectl"
+    echo "DRY-RUN: The downloaded binary would be installed to ${KUBECTL_DEST}."
+    echo "DRY-RUN: The temporary file /tmp/kubectl would be removed."
+    
+    echo
+    echo "Dry-Run complete. No changes were made."
+else    
+    if [ -f "${KUBECTL_DEST}" ]; then
+        echo "Existing kubectl binary found. Reading and preserving permissions/ownership for ${KUBECTL_DEST}..."
+        
+        OWNER_UID=$(sudo stat -c "%u" "${KUBECTL_DEST}" 2>/dev/null)
+        OWNER_GID=$(sudo stat -c "%g" "${KUBECTL_DEST}" 2>/dev/null)
+        OLD_MODE=$(sudo stat -c "%a" "${KUBECTL_DEST}" 2>/dev/null)
+
+        if [ -n "$OLD_MODE" ]; then
+            INSTALL_MODE="$OLD_MODE"
+            echo "Preserving permissions: ${INSTALL_MODE}"
+        fi
+        
+        if [ "$OWNER_UID" == "0" ]; then OWNER_UID="root"; fi
+        if [ "$OWNER_GID" == "0" ]; then OWNER_GID="root"; fi
+
+        if [ -n "$OWNER_UID" ] && [ -n "$OWNER_GID" ]; then
+            echo "Preserving ownership: Owner=${OWNER_UID}, Group=${OWNER_GID}"
+        else
+             echo "Could not read existing ownership/permissions, defaulting to root:root and 0755."
+             OWNER_UID="root"
+             OWNER_GID="root"
+        fi
+
+        echo "Removing existing kubectl binary at ${KUBECTL_DEST}..."
+        sudo rm -f "${KUBECTL_DEST}"
+    else
+        echo "No existing kubectl binary found at ${KUBECTL_DEST}. Installing new binary with default permissions."
+    fi
+    
+    echo "Downloading kubectl v${KUBE_VERSION} from: ${DOWNLOAD_URL}"
+    curl -sSL "${DOWNLOAD_URL}" -o /tmp/kubectl
+
+    if [ ! -s "/tmp/kubectl" ]; then
+        echo "Error: Download failed or the binary file is empty. Check the version number (v${KUBE_VERSION}) or URL." >&2
+        rm -f /tmp/kubectl
+        exit 1
+    fi
+
+    echo "Installing kubectl to ${KUBECTL_DEST} with mode ${INSTALL_MODE} and ownership ${OWNER_UID}:${OWNER_GID}..."
+    
+    sudo install -o "${OWNER_UID}" -g "${OWNER_GID}" -m "${INSTALL_MODE}" /tmp/kubectl "${KUBECTL_DEST}"
+    rm -f /tmp/kubectl
+
+    echo "Installation complete!"
+    echo "New kubectl version:"
+    ${KUBECTL_DEST} version --client
+
+    echo ""
+    echo "Server version check:"
+    ${KUBECTL_DEST} version --client=false
+fi