added ability to copy files into the built image's filesystem (#474)

* added ability to copy files into the built image's filesystem

* changed os-files implementation to use the existing CopyFiles function

* incorporated PR feedback

RELEASE_NOTES.md

@@ -4,12 +4,16 @@
 
 ## General
 
+* Added the ability to automatically copy files into the built images filesystem
+
 ## API
 
 ### Image Definition Changes
 
 ### Image Configuration Directory Changes
 
+* An optional directory named `os-files` may be included to copy files into the resulting image's filesystem at runtime
+
 ## Bug Fixes
 
 ---

docs/building-images.md

@@ -473,6 +473,24 @@ the built image and used to register with Elemental on boot.
 > ```podman run``` command. For more info on why this is required, please see
 > [Package resolution design](design/pkg-resolution.md#running-the-eib-container).
 
+## Operating System Files
+
+Files placed in the `os-files` directory in the image configuration directory will be automatically copied
+into the filesystem of the built image. The exact directory structure will be retained when they are copied.
+For example, if a file exists in a subdirectory named `os-files/etc`, it will be placed in the `/etc` directory
+of the built image.
+
+If the `os-files` directory exists, it cannot be empty.
+
+```bash
+.
+├── definition.yaml
+└── os-files
+    └── etc
+        └── ssh
+            └── sshd_config
+```
+
 ## Custom
 
 EIB has the ability to bundle in custom scripts that will be run during the combustion phase when a node is

pkg/combustion/combustion.go

@@ -120,6 +120,10 @@ func (c *Combustion) Configure(ctx *image.Context) error {
 			name:     rpmComponentName,
 			runnable: c.configureRPMs,
 		},
+		{
+			name:     osFilesComponentName,
+			runnable: configureOSFiles,
+		},
 		{
 			name:     systemdComponentName,
 			runnable: configureSystemd,

pkg/combustion/osfiles.go

@@ -0,0 +1,77 @@
+package combustion
+
+import (
+	_ "embed"
+	"fmt"
+	"os"
+	"path/filepath"
+
+	"github.com/suse-edge/edge-image-builder/pkg/fileio"
+	"github.com/suse-edge/edge-image-builder/pkg/image"
+	"github.com/suse-edge/edge-image-builder/pkg/log"
+	"go.uber.org/zap"
+)
+
+const (
+	osFilesComponentName = "os files"
+	osFilesConfigDir     = "os-files"
+	osFilesScriptName    = "19-copy-os-files.sh"
+	osFilesLogFile       = "copy-os-files.log"
+)
+
+var (
+	//go:embed templates/19-copy-os-files.sh
+	osFilesScript string
+)
+
+func configureOSFiles(ctx *image.Context) ([]string, error) {
+	if !isComponentConfigured(ctx, osFilesConfigDir) {
+		log.AuditComponentSkipped(osFilesComponentName)
+		zap.S().Info("skipping os files component, no files provided")
+		return nil, nil
+	}
+
+	if err := copyOSFiles(ctx); err != nil {
+		log.AuditComponentFailed(osFilesComponentName)
+		return nil, err
+	}
+
+	if err := writeOSFilesScript(ctx); err != nil {
+		log.AuditComponentFailed(osFilesComponentName)
+		return nil, err
+	}
+
+	log.AuditComponentSuccessful(osFilesComponentName)
+	return []string{osFilesScriptName}, nil
+}
+
+func copyOSFiles(ctx *image.Context) error {
+	srcDirectory := filepath.Join(ctx.ImageConfigDir, osFilesConfigDir)
+	destDirectory := filepath.Join(ctx.CombustionDir, osFilesConfigDir)
+
+	dirEntries, err := os.ReadDir(srcDirectory)
+	if err != nil {
+		return fmt.Errorf("reading the os files directory at %s: %w", srcDirectory, err)
+	}
+
+	// If the directory exists but there's nothing in it, consider it an error case
+	if len(dirEntries) == 0 {
+		return fmt.Errorf("no files found in directory %s", srcDirectory)
+	}
+
+	if err := fileio.CopyFiles(srcDirectory, destDirectory, "", true); err != nil {
+		return fmt.Errorf("copying os-files: %w", err)
+	}
+
+	return nil
+}
+
+func writeOSFilesScript(ctx *image.Context) error {
+	osFilesScriptFilename := filepath.Join(ctx.CombustionDir, osFilesScriptName)
+
+	if err := os.WriteFile(osFilesScriptFilename, []byte(osFilesScript), fileio.ExecutablePerms); err != nil {
+		return fmt.Errorf("writing os files script %s: %w", osFilesScriptFilename, err)
+	}
+
+	return nil
+}

pkg/combustion/osfiles_test.go

@@ -0,0 +1,71 @@
+package combustion
+
+import (
+	"fmt"
+	"os"
+	"path/filepath"
+	"testing"
+
+	"github.com/stretchr/testify/assert"
+	"github.com/stretchr/testify/require"
+	"github.com/suse-edge/edge-image-builder/pkg/image"
+)
+
+func setupOsFilesConfigDir(t *testing.T, empty bool) (ctx *image.Context, teardown func()) {
+	ctx, teardown = setupContext(t)
+
+	testOsFilesDir := filepath.Join(ctx.ImageConfigDir, osFilesConfigDir)
+	err := os.Mkdir(testOsFilesDir, 0o755)
+	require.NoError(t, err)
+
+	if !empty {
+		nestedOsFilesDir := filepath.Join(testOsFilesDir, "etc", "ssh")
+		err = os.MkdirAll(nestedOsFilesDir, 0o755)
+		require.NoError(t, err)
+
+		testFile := filepath.Join(nestedOsFilesDir, "test-config-file")
+		_, err = os.Create(testFile)
+		require.NoError(t, err)
+	}
+
+	return
+}
+
+func TestConfigureOSFiles(t *testing.T) {
+	// Setup
+	ctx, teardown := setupOsFilesConfigDir(t, false)
+	defer teardown()
+
+	// Test
+	scriptNames, err := configureOSFiles(ctx)
+
+	// Verify
+	require.NoError(t, err)
+
+	assert.Equal(t, []string{osFilesScriptName}, scriptNames)
+
+	// -- Combustion Script
+	expectedCombustionScript := filepath.Join(ctx.CombustionDir, osFilesScriptName)
+	contents, err := os.ReadFile(expectedCombustionScript)
+	require.NoError(t, err)
+	assert.Contains(t, string(contents), "cp -R")
+
+	// -- Files
+	expectedFile := filepath.Join(ctx.CombustionDir, osFilesConfigDir, "etc", "ssh", "test-config-file")
+	assert.FileExists(t, expectedFile)
+}
+
+func TestConfigureOSFiles_EmptyDirectory(t *testing.T) {
+	// Setup
+	ctx, teardown := setupOsFilesConfigDir(t, true)
+	defer teardown()
+
+	// Test
+	scriptName, err := configureOSFiles(ctx)
+
+	// Verify
+	assert.Nil(t, scriptName)
+
+	srcDirectory := filepath.Join(ctx.ImageConfigDir, osFilesConfigDir)
+	assert.EqualError(t, err, fmt.Sprintf("no files found in directory %s", srcDirectory))
+}

pkg/combustion/templates/19-copy-os-files.sh

@@ -0,0 +1,4 @@
+#!/bin/bash
+set -euo pipefail
+
+cp -R ./os-files/* /