add nsswitch to busybox control plane images

build/BUILD

 package(default_visibility = ["//visibility:public"])
 
 load("@io_bazel_rules_docker//docker:docker.bzl", "docker_build", "docker_bundle")
+load("@io_bazel_rules_docker//container:container.bzl", "container_image")
 load("@io_kubernetes_build//defs:build.bzl", "release_filegroup")
 
 filegroup(
@@ -21,23 +22,32 @@ filegroup(
     tags = ["automanaged"],
 )
 
+# ensure /etc/nsswitch.conf exists so go's resolver respects /etc/hosts
+container_image(
+    name = "busybox-with-nsswitch",
+    base = "@official_busybox//image",
+    directory = "/etc",
+    files = ["nsswitch.conf"],
+    mode = "0644",
+)
+
 # This list should roughly match kube::build::get_docker_wrapped_binaries()
 # in build/common.sh.
 DOCKERIZED_BINARIES = {
     "cloud-controller-manager": {
-        "base": "@official_busybox//image",
+        "base": ":busybox-with-nsswitch",
         "target": "//cmd/cloud-controller-manager:cloud-controller-manager",
     },
     "kube-apiserver": {
-        "base": "@official_busybox//image",
+        "base": ":busybox-with-nsswitch",
         "target": "//cmd/kube-apiserver:kube-apiserver",
     },
     "kube-controller-manager": {
-        "base": "@official_busybox//image",
+        "base": ":busybox-with-nsswitch",
         "target": "//cmd/kube-controller-manager:kube-controller-manager",
     },
     "kube-scheduler": {
-        "base": "@official_busybox//image",
+        "base": ":busybox-with-nsswitch",
         "target": "//cmd/kube-scheduler:kube-scheduler",
     },
     "kube-proxy": {

build/lib/release.sh

@@ -355,8 +355,16 @@ function kube::release::create_docker_images_for_server() {
         rm -rf "${docker_build_path}"
         mkdir -p "${docker_build_path}"
         ln "${binary_dir}/${binary_name}" "${docker_build_path}/${binary_name}"
-        printf " FROM ${base_image} \n ADD ${binary_name} /usr/local/bin/${binary_name}\n" > "${docker_file_path}"
-
+        ln "${KUBE_ROOT}/build/nsswitch.conf" "${docker_build_path}/nsswitch.conf"
+        chmod 0644 "${docker_build_path}/nsswitch.conf"
+        cat <<EOF > "${docker_file_path}"
+FROM ${base_image}
+COPY ${binary_name} /usr/local/bin/${binary_name}
+EOF
+        # ensure /etc/nsswitch.conf exists so go's resolver respects /etc/hosts
+        if [[ "${base_image}" =~ busybox ]]; then
+          echo "COPY nsswitch.conf /etc/" >> "${docker_file_path}"
+        fi
         "${DOCKER[@]}" build --pull -q -t "${docker_image_tag}" "${docker_build_path}" >/dev/null
         "${DOCKER[@]}" tag "${docker_image_tag}" "${deprecated_image_tag}" >/dev/null
         "${DOCKER[@]}" save "${docker_image_tag}" "${deprecated_image_tag}" > "${binary_dir}/${binary_name}.tar"

build/nsswitch.conf

+# ensure go's non-cgo resolver respects /etc/hosts
+hosts: files dns