Pros of moby

• More comprehensive project covering entire container ecosystem
• Larger community and more active development
• Includes runtime implementation and additional tools

Cons of moby

• More complex and harder to understand for newcomers
• Less focused on standardization compared to image-spec
• Potentially slower to adopt new features due to larger codebase

Code comparison

image-spec:

type Image struct {
    Config Descriptor   `json:"config"`
    Layers []Descriptor `json:"layers"`
}

moby:

type Image struct {
    V1Image
    Parent     string    `json:"parent,omitempty"`
    Container  string    `json:"container,omitempty"`
    Config     *Config   `json:"config,omitempty"`
    Architecture string  `json:"architecture,omitempty"`
    OS          string   `json:"os,omitempty"`
}

Summary

image-spec focuses on standardizing container image format, while moby is a broader project encompassing various container-related components. image-spec provides a clear, concise specification, making it easier for implementers to understand and adopt. moby, on the other hand, offers a complete container solution with runtime implementation and additional tools, but at the cost of increased complexity. Both projects contribute significantly to the container ecosystem, with image-spec emphasizing standardization and moby providing a comprehensive platform for container operations.

Pros of containerd

• Provides a complete container runtime implementation
• Offers broader functionality beyond image specifications
• Actively maintained with frequent updates and community support

Cons of containerd

• More complex and resource-intensive
• Steeper learning curve for newcomers
• May include features unnecessary for simple container management

Code Comparison

image-spec:

type Image struct {
    Config Descriptor   `json:"config"`
    Layers []Descriptor `json:"layers"`
}

containerd:

type Container struct {
    ID        string
    Image     string
    Runtime   string
    Spec      *specs.Spec
    Task      Task
}

Summary

image-spec focuses on defining standards for container images, while containerd provides a full container runtime implementation. image-spec is more lightweight and specific to image formats, making it easier to understand and implement for image-related tasks. containerd offers a comprehensive solution for container management but may be overkill for projects only needing image handling.

image-spec is ideal for developers working on tools that interact with container images, while containerd is better suited for building complete container management systems or integrating container functionality into larger projects.

Both projects are valuable in the container ecosystem, with image-spec providing the foundation for standardized image formats and containerd offering a robust runtime implementation that adheres to these standards.

Pros of docker-ce

• Comprehensive container platform with a full suite of tools
• Widely adopted and supported by a large community
• Includes Docker Engine, CLI, and additional features like Swarm mode

Cons of docker-ce

• Larger codebase and more complex architecture
• Less focused on standardization compared to image-spec
• May include proprietary components not compatible with other container runtimes

Code Comparison

image-spec:

{
  "schemaVersion": 2,
  "mediaType": "application/vnd.oci.image.manifest.v1+json",
  "config": {
    "mediaType": "application/vnd.oci.image.config.v1+json",
    "size": 7023,
    "digest": "sha256:b5b2b2c507a0944348e0303114d8d93aaaa081732b86451d9bce1f432a537bc7"
  }
}

docker-ce:

func (daemon *Daemon) containerStart(container *container.Container, checkpoint string, checkpointDir string, resetRestartManager bool) (err error) {
	container.Lock()
	defer container.Unlock()

	if resetRestartManager && container.RestartManager != nil {
		container.RestartManager.Cancel()
	}
}

Summary

image-spec focuses on defining a standard format for container images, promoting interoperability between different container runtimes. docker-ce, on the other hand, provides a full-featured container platform with additional tools and capabilities. While docker-ce offers a more comprehensive solution, image-spec aims for simplicity and standardization across the container ecosystem.

Pros of pack

• Simplifies the container build process with a higher-level abstraction
• Supports multiple programming languages and frameworks out-of-the-box
• Provides automatic dependency management and runtime detection

Cons of pack

• Less flexibility in fine-tuning container images compared to direct OCI spec usage
• May introduce additional complexity for advanced use cases
• Limited control over the underlying image structure

Code Comparison

pack:

pack build myapp --builder cnbs/sample-builder:bionic

image-spec:

{
  "schemaVersion": 2,
  "config": {
    "mediaType": "application/vnd.oci.image.config.v1+json",
    "size": 7023,
    "digest": "sha256:b5b2b2c507a0944348e0303114d8d93aaaa081732b86451d9bce1f432a537bc7"
  }
}

pack focuses on simplifying the build process with a single command, while image-spec provides a low-level specification for container images. pack abstracts away many details, making it easier for developers to create container images without deep knowledge of the underlying structure. However, this abstraction can limit flexibility for advanced users who need fine-grained control over image composition.

image-spec, on the other hand, offers a standardized format for container images, allowing for greater interoperability and customization. It provides a foundation for tools like pack to build upon, ensuring compatibility across different container runtimes and platforms.

Pros of skopeo

• Practical tool for container image operations (copying, inspecting, deleting)
• Supports multiple image formats and registries
• Actively maintained with regular updates and bug fixes

Cons of skopeo

• Focused on image operations rather than standardization
• May have compatibility issues with non-standard image formats
• Requires installation and setup, unlike a specification document

Code comparison

image-spec (JSON schema example):

{
  "mediaType": "application/vnd.oci.image.manifest.v1+json",
  "schemaVersion": 2,
  "config": {
    "mediaType": "application/vnd.oci.image.config.v1+json",
    "size": 7023,
    "digest": "sha256:b5b2b2c507a0944348e0303114d8d93aaaa081732b86451d9bce1f432a537bc7"
  }
}

skopeo (command-line usage example):

skopeo copy docker://registry.example.com/image:tag \
             docker://registry.example.com/image:newtag

Summary

image-spec is a standardization effort for container image formats, while skopeo is a practical tool for working with container images. image-spec provides a specification for image formats, ensuring consistency across different container technologies. skopeo, on the other hand, offers hands-on functionality for managing and manipulating container images across various registries and formats. While image-spec focuses on standardization, skopeo provides practical utility for container image operations.