Add build command for OCI images

This command automates the steps for building OCI images from
checkpoint archives.

Signed-off-by: Parthiba-Hazra <parthibahazra@gmail.com>
Signed-off-by: Radostin Stoyanov <rstoyanov@fedoraproject.org>

Author: rst0git

checkpointctl.go

@@ -31,6 +31,8 @@ func main() {
 
 	rootCommand.AddCommand(cmd.List())
 
+	rootCommand.AddCommand(cmd.BuildCmd())
+
 	rootCommand.Version = version
 
 	if err := rootCommand.Execute(); err != nil {

cmd/build.go

@@ -0,0 +1,47 @@
+// SPDX-License-Identifier: Apache-2.0
+
+package cmd
+
+import (
+	"context"
+	"fmt"
+	"log"
+
+	"github.com/checkpoint-restore/checkpointctl/internal"
+	"github.com/spf13/cobra"
+)
+
+func BuildCmd() *cobra.Command {
+	cmd := &cobra.Command{
+		Use:   "build <checkpoint-path> <image-name>",
+		Short: "Create an OCI image from a container checkpoint archive",
+		Long: `The 'build' command converts a container checkpoint archive into an OCI-compatible image.
+Metadata from the checkpoint archive is extracted and applied as OCI image annotations.
+Example:
+  checkpointctl build checkpoint.tar quay.io/foo/bar:latest
+  buildah push quay.io/foo/bar:latest`,
+		Args: cobra.ExactArgs(2),
+		RunE: convertArchive,
+	}
+
+	return cmd
+}
+
+func convertArchive(cmd *cobra.Command, args []string) error {
+	if len(args) != 2 {
+		return fmt.Errorf("please provide both the checkpoint path and the image name")
+	}
+
+	checkpointPath := args[0]
+	imageName := args[1]
+
+	ImageBuilder := internal.NewImageBuilder(imageName, checkpointPath)
+
+	err := ImageBuilder.CreateImageFromCheckpoint(context.Background())
+	if err != nil {
+		return err
+	}
+
+	log.Printf("Image '%s' created successfully from checkpoint '%s'\n", imageName, checkpointPath)
+	return nil
+}

docs/checkpointctl-build.adoc

@@ -0,0 +1,29 @@
+= checkpointctl-build(1)
+include::footer.adoc[]
+
+== Name
+
+*checkpointctl-build* - Create OCI image from a checkpoint tar file.
+
+== Synopsis
+
+*checkpointctl build* CHECKPOINT_PATH IMAGE_NAME
+
+== Options
+
+*-h*, *--help*::
+  Show help for checkpointctl build
+
+== Description
+
+Create an OCI image from a container checkpoint archive (tar file) using `buildah`.
+The checkpoint metadata is extracted from the archive and applied as OCI image annotations,
+allowing the container runtime (Podman, CRI-O, containerd) to identify the image as a checkpoint.
+
+Usage Example:
+  `checkpointctl build checkpoint.tar quay.io/foo/bar:latest`
+  `buildah push quay.io/foo/bar:latest`
+
+== See also
+
+checkpointctl(1)

internal/oci_image_build.go

@@ -0,0 +1,134 @@
+package internal
+
+import (
+	"bytes"
+	"context"
+	"fmt"
+	"log"
+	"os"
+	"os/exec"
+	"strings"
+
+	metadata "github.com/checkpoint-restore/checkpointctl/lib"
+)
+
+type ImageBuilder struct {
+	imageName      string
+	checkpointPath string
+}
+
+func NewImageBuilder(imageName, checkpointPath string) *ImageBuilder {
+	return &ImageBuilder{
+		imageName:      imageName,
+		checkpointPath: checkpointPath,
+	}
+}
+
+func runBuildahCommand(args ...string) (string, error) {
+	cmd := exec.Command("buildah", args...)
+
+	var out bytes.Buffer
+	var stderr bytes.Buffer
+	cmd.Stdout = &out
+	cmd.Stderr = &stderr
+
+	err := cmd.Run()
+	if err != nil {
+		return "", fmt.Errorf("buildah command failed: error: %w, stderr: %s", err, stderr.String())
+	}
+
+	return out.String(), nil
+}
+
+func (ic *ImageBuilder) CreateImageFromCheckpoint(ctx context.Context) error {
+	// Step 1: Create a new container from scratch
+	newContainer, err := runBuildahCommand("from", "scratch")
+	if err != nil {
+		return fmt.Errorf("creating container failed: %w", err)
+	}
+	newContainer = strings.TrimSpace(newContainer)
+
+	// Ensure the container is removed in case of failure
+	defer func() {
+		if newContainer != "" {
+			_, err := runBuildahCommand("rm", newContainer)
+			if err != nil {
+				fmt.Printf("Warning: failed to remove container %s: %v\n", newContainer, err)
+			}
+		}
+	}()
+
+	// Step 2: Add checkpoint files to the container
+	_, err = runBuildahCommand("add", newContainer, ic.checkpointPath)
+	if err != nil {
+		return fmt.Errorf("adding files to container failed: %w", err)
+	}
+
+	// Step 3: Apply checkpoint annotations
+	checkpointImageAnnotations, err := ic.getCheckpointAnnotations()
+	if err != nil {
+		return fmt.Errorf("extracting checkpoint annotations failed: %w", err)
+	}
+
+	for key, value := range checkpointImageAnnotations {
+		_, err := runBuildahCommand("config", "--annotation", fmt.Sprintf("%s=%s", key, value), newContainer)
+		if err != nil {
+			fmt.Printf("Error setting annotation %s=%s: %v\n", key, value, err)
+		} else {
+			fmt.Printf("Added annotation: %s=%s\n", key, value)
+		}
+	}
+
+	// Step 4: Commit the container to an image
+	_, err = runBuildahCommand("commit", newContainer, ic.imageName)
+	if err != nil {
+		return fmt.Errorf("committing container annotations failed: %w", err)
+	}
+
+	return nil
+}
+
+func (ic *ImageBuilder) getCheckpointAnnotations() (map[string]string, error) {
+	checkpointImageAnnotations := map[string]string{}
+
+	// Create a temporary directory
+	tempDir, err := os.MkdirTemp("", "checkpoint-extract-")
+	if err != nil {
+		log.Printf("Error creating temporary directory: %v\n", err)
+		return nil, err
+	}
+	defer os.RemoveAll(tempDir)
+
+	filesToExtract := []string{"spec.dump", "config.dump"}
+	if err = UntarFiles(ic.checkpointPath, tempDir, filesToExtract); err != nil {
+		log.Printf("Error extracting files from archive %s: %v\n", ic.checkpointPath, err)
+		return nil, err
+	}
+
+	info := &checkpointInfo{}
+	info.configDump, _, err = metadata.ReadContainerCheckpointConfigDump(tempDir)
+	if err != nil {
+		return nil, err
+	}
+
+	info.specDump, _, err = metadata.ReadContainerCheckpointSpecDump(tempDir)
+	if err != nil {
+		return nil, err
+	}
+
+	info.containerInfo, err = getContainerInfo(info.specDump, info.configDump)
+	if err != nil {
+		return nil, err
+	}
+
+	checkpointImageAnnotations[metadata.CheckpointAnnotationEngine] = info.containerInfo.Engine
+	checkpointImageAnnotations[metadata.CheckpointAnnotationName] = info.containerInfo.Name
+	checkpointImageAnnotations[metadata.CheckpointAnnotationPod] = info.containerInfo.Pod
+	checkpointImageAnnotations[metadata.CheckpointAnnotationNamespace] = info.containerInfo.Namespace
+	checkpointImageAnnotations[metadata.CheckpointAnnotationRootfsImageUserRequested] = info.configDump.RootfsImage
+	checkpointImageAnnotations[metadata.CheckpointAnnotationRootfsImageName] = info.configDump.RootfsImageName
+	checkpointImageAnnotations[metadata.CheckpointAnnotationRootfsImageID] = info.configDump.RootfsImageRef
+	checkpointImageAnnotations[metadata.CheckpointAnnotationRuntimeName] = info.configDump.OCIRuntime
+
+	return checkpointImageAnnotations, nil
+}