How do I install dgr on Ubuntu?

Download the Linux 64-bit executable from the releases page, place it in your PATH, and ensure rkt is installed. Basic configuration can be set in ~/.config/dgr/config.yml, but it's optional if rkt is available.

dgr vs Dockerfile: which is better for runtime configuration?

dgr excels with its templating and attribute system for runtime configuration without image rebuilds, while Dockerfiles are static and require rebuilds for changes. Choose dgr if you need dynamic, environment-specific setups for rkt-based containers.

Can dgr build Docker images?

No, dgr is designed for App Container Images (ACI) used with rkt. The README mentions future OCI support, but currently it does not output Docker-compatible images, limiting interoperability with Docker ecosystems.

How does dgr handle environment variables in builds?

dgr imports environment variables prefixed with DGR_ENV_ automatically, and you can use --set-env to pass others to the builder. This allows proxy settings or custom configs without hardcoding, as explained in the 'How it's working' section.

What are the system requirements for running dgr?

You need rkt installed, root access for container operations, and a Linux kernel >= 3.18 with overlay filesystem support. Check the requirements section for specifics on dependencies and setup.

Is dgr suitable for use with Kubernetes?

Not directly, as dgr focuses on rkt and ACI, which are not native to Kubernetes. While rkt can run in Kubernetes, dgr's tooling is optimized for the App Container spec, so it's less ideal for Kubernetes-centric workflows.

dgr — App Container Image Builder

What is dgr?

dgr is a command-line utility for building and configuring App Container Images (ACI) and pods. It follows the App Container (appc) specification and uses convention over configuration to create generic images that can be customized at runtime. The tool solves the problem of environment-specific container configurations by separating build-time and runtime concerns.

Target Audience

DevOps engineers and platform teams managing containerized applications with rkt, especially those needing runtime configuration and templating for multi-environment deployments.

Value Proposition

Developers choose dgr for its strong runtime configuration capabilities, support for the App Container spec, and ability to build generic images that adapt to different environments without duplication. Its integrated templating and script runlevels provide flexibility not found in simpler build tools.

Container build and runtime tool

Use Cases

Best For

Building App Container Images (ACI) for rkt runtime
Configuring containerized applications at runtime for different environments
Managing container dependencies and overlays in multi-layer deployments
Creating reusable container images with templated configuration files
Integrating container builds into CI/CD pipelines with testing
Orchestrating pods as a unit for multi-service applications

Not Ideal For

Projects exclusively using Docker and not interested in adopting rkt or the App Container spec
Teams needing immediate Open Container Initiative (OCI) compliance without waiting for future support
Simple container builds where runtime templating and script runlevels add unnecessary overhead
Environments without root access or Linux kernel support for overlay filesystem

Pros & Cons

Pros

Runtime Templating Power

Uses Go templating with built-in functions to dynamically generate configuration files at container start, enabling the same image to adapt to different environments without rebuilds, as highlighted in the templates section.

Flexible Script Runlevels

Executes scripts at multiple stages like build, prestart, and inherit, providing fine-grained control over container setup and customization, detailed in the runlevels documentation.

Integrated Testing Framework

Includes a built-in test system that can be extended to support various testing frameworks, allowing automated ACI testing within the build process, as mentioned in the commands and features.

Pod as a Unit

Builds and manages pods as cohesive groups of ACIs, enabling orchestration of multi-service applications during both build and runtime, which is a key feature outlined in the pod support section.

Cons

Niche Runtime Dependency

Heavily reliant on rkt and the App Container spec, which have smaller adoption compared to Docker, limiting community support, tooling, and future compatibility, as noted in the comparison and requirements.

Root and Kernel Requirements

Requires root privileges to run rkt and a Linux kernel >= 3.18 with overlay filesystem, making it unsuitable for restricted, non-Linux, or legacy environments, as specified in the requirements section.

Incomplete Documentation

Some parts of the README, such as detailed pod building instructions, are marked as TODO, indicating gaps that could hinder learning and implementation for new users.

What is dgr?

Target Audience

DevOps engineers and platform teams managing containerized applications with rkt, especially those needing runtime configuration and templating for multi-environment deployments.

Value Proposition

Use Cases

Best For

Building App Container Images (ACI) for rkt runtime
Configuring containerized applications at runtime for different environments
Managing container dependencies and overlays in multi-layer deployments
Creating reusable container images with templated configuration files
Integrating container builds into CI/CD pipelines with testing
Orchestrating pods as a unit for multi-service applications

Not Ideal For

Projects exclusively using Docker and not interested in adopting rkt or the App Container spec
Teams needing immediate Open Container Initiative (OCI) compliance without waiting for future support
Simple container builds where runtime templating and script runlevels add unnecessary overhead
Environments without root access or Linux kernel support for overlay filesystem

Pros & Cons

Pros

Runtime Templating Power

Flexible Script Runlevels

Executes scripts at multiple stages like build, prestart, and inherit, providing fine-grained control over container setup and customization, detailed in the runlevels documentation.

Integrated Testing Framework

Includes a built-in test system that can be extended to support various testing frameworks, allowing automated ACI testing within the build process, as mentioned in the commands and features.

Pod as a Unit

Builds and manages pods as cohesive groups of ACIs, enabling orchestration of multi-service applications during both build and runtime, which is a key feature outlined in the pod support section.

Cons

Niche Runtime Dependency

Root and Kernel Requirements

Incomplete Documentation

Some parts of the README, such as detailed pod building instructions, are marked as TODO, indicating gaps that could hinder learning and implementation for new users.

dgr

What is dgr?

Overview

Use Cases

Best For

Not Ideal For

Pros & Cons

Pros

Cons

Frequently Asked Questions

Related Projects

Found a gem we're missing?

dgr

What is dgr?

Overview

Use Cases

Best For

Not Ideal For

Pros & Cons

Pros

Cons

Frequently Asked Questions

Related Projects

Found a gem we're missing?