Marshal containerd.toml instead of templating it

pkg/component/worker/containerd/component.go

@@ -28,17 +28,16 @@ import (
 	"os"
 	"path/filepath"
 	"runtime"
-	"strings"
 	"syscall"
 	"time"
 
+	"github.com/BurntSushi/toml"
 	"github.com/fsnotify/fsnotify"
 	"github.com/sirupsen/logrus"
 	"golang.org/x/sync/errgroup"
 
 	"github.com/k0sproject/k0s/internal/pkg/dir"
 	"github.com/k0sproject/k0s/internal/pkg/file"
-	"github.com/k0sproject/k0s/internal/pkg/templatewriter"
 	"github.com/k0sproject/k0s/pkg/assets"
 	"github.com/k0sproject/k0s/pkg/component/manager"
 	workerconfig "github.com/k0sproject/k0s/pkg/component/worker/config"
@@ -48,16 +47,10 @@ import (
 	"github.com/k0sproject/k0s/pkg/supervisor"
 )
 
-const confTmpl = `# k0s_managed=true
+const containerdTomlHeader = `# k0s_managed=true
 # This is a placeholder configuration for k0s managed containerd.
 # If you wish to override the config, remove the first line and replace this file with your custom configuration.
 # For reference see https://github.com/containerd/containerd/blob/main/docs/man/containerd-config.toml.5.md
-version = 2
-imports = [
-	{{- range $i := .Imports }}
-	"{{ $i }}",
-	{{- end }}
-]
 `
 const confPathPosix = "/etc/k0s/containerd.toml"
 const confPathWindows = "C:\\Program Files\\containerd\\config.toml"
@@ -205,33 +198,32 @@ func (c *Component) setupConfig() error {
 	}
 
 	criConfigPath := filepath.Join(c.K0sVars.RunDir, "containerd-cri.toml")
-	err = file.WriteContentAtomically(criConfigPath, []byte(config.CRIConfig), 0644)
-	if err != nil {
-		return fmt.Errorf("can't create containerd CRI config: %w", err)
-	}
 
-	var data struct{ Imports []string }
-	data.Imports = append(config.ImportPaths, criConfigPath)
-
-	// double escape for windows because containerd expects
-	// double backslash in the configuration but golang templates
-	// unescape double slash to a single slash
-	if runtime.GOOS == "windows" {
-		for i := range data.Imports {
-			data.Imports[i] = strings.ReplaceAll(data.Imports[i], "\\", "\\\\")
-		}
+	if err = file.AtomicWithTarget(criConfigPath).
+		WithPermissions(0644).
+		WriteString(config.CRIConfig); err != nil {
+		return fmt.Errorf("can't create containerd CRI config: %w", err)
 	}
 
-	output := bytes.NewBuffer([]byte{})
-	tw := templatewriter.TemplateWriter{
-		Name:     "containerdconfig",
-		Template: confTmpl,
-		Data:     data,
-	}
-	if err := tw.WriteToBuffer(output); err != nil {
+	if err := file.AtomicWithTarget(c.confPath).
+		WithPermissions(0644).
+		Do(func(f file.AtomicWriter) error {
+			w := bufio.NewWriter(f)
+			if _, err := w.WriteString(containerdTomlHeader); err != nil {
+				return err
+			}
+			if err := toml.NewEncoder(w).Encode(map[string]any{
+				"version": 2,
+				"imports": append(config.ImportPaths, criConfigPath),
+			}); err != nil {
+				return err
+			}
+			return w.Flush()
+		}); err != nil {
 		return fmt.Errorf("can't create containerd config: %w", err)
 	}
-	return file.WriteContentAtomically(c.confPath, output.Bytes(), 0644)
+
+	return nil
 }
 
 func (c *Component) watchDropinConfigs(ctx context.Context) {

pkg/component/worker/containerd/configurer.go

@@ -109,21 +109,18 @@ func generateDefaultCRIConfig(sandboxContainerImage string) ([]byte, error) {
 	// Set pause image
 	criPluginConfig.SandboxImage = sandboxContainerImage
 	if runtime.GOOS == "windows" {
-		criPluginConfig.CniConfig.NetworkPluginBinDir = "c:\\opt\\cni\\bin"
-		criPluginConfig.CniConfig.NetworkPluginConfDir = "c:\\opt\\cni\\conf"
+		// The default config for Windows uses %ProgramFiles%/containerd/cni/{bin,conf}.
+		// Maybe k0s can use the default in the future, so there's no need for this override.
+		criPluginConfig.CniConfig.NetworkPluginBinDir = `c:\opt\cni\bin`
+		criPluginConfig.CniConfig.NetworkPluginConfDir = `c:\opt\cni\conf`
 	}
-	// We need to use custom struct so we can unmarshal the CRI plugin config only
-	containerdConfig := struct {
-		Version int                    `toml:"version"`
-		Plugins map[string]interface{} `toml:"plugins"`
-	}{
-		Version: 2,
-		Plugins: map[string]interface{}{
+
+	return toml.Marshal(map[string]any{
+		"version": 2,
+		"plugins": map[string]any{
 			"io.containerd.grpc.v1.cri": criPluginConfig,
 		},
-	}
-
-	return toml.Marshal(containerdConfig)
+	})
 }
 
 func hasCRIPluginConfig(data []byte) (bool, error) {

pkg/component/worker/containerd/configurer_test.go

@@ -39,8 +39,9 @@ func TestConfigurer_HandleImports(t *testing.T) {
 		err := os.WriteFile(filepath.Join(importsPath, "foo.toml"), []byte(criRuntimeConfig), 0644)
 		require.NoError(t, err)
 		c := configurer{
-			loadPath: filepath.Join(importsPath, "*.toml"),
-			log:      logrus.New().WithField("test", t.Name()),
+			loadPath:   filepath.Join(importsPath, "*.toml"),
+			pauseImage: "pause:42",
+			log:        logrus.New().WithField("test", t.Name()),
 		}
 		criConfig, err := c.handleImports()
 		assert.NoError(t, err)
@@ -60,8 +61,10 @@ func TestConfigurer_HandleImports(t *testing.T) {
 		assert.Equal(t, 2, containerdConfig.Version)
 		criPluginConfig := containerdConfig.Plugins["io.containerd.grpc.v1.cri"]
 		require.NotNil(t, criPluginConfig, "No CRI plugin configuration section found")
+		sandboxImage := criPluginConfig.Get("sandbox_image")
+		assert.Equal(t, "pause:42", sandboxImage, "Custom pause image not found in CRI configuration")
 		snapshotter := criPluginConfig.GetPath([]string{"containerd", "snapshotter"})
-		require.Equal(t, "zfs", snapshotter)
+		assert.Equal(t, "zfs", snapshotter, "Overridden snapshotter not found in CRI configuration")
 	})
 
 	t.Run("should have no imports if imports dir is empty", func(t *testing.T) {