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libpod - library for running OCI-based containers in Pods

Latest Version:

Status: Active Development

What is the scope of this project?

libpod provides a library for applications looking to use the Container Pod concept popularized by Kubernetes. libpod also contains a tool called podman for managing Pods, Containers, and Container Images.

At a high level, the scope of libpod and podman is the following:

  • Support multiple image formats including the existing Docker/OCI image formats.
  • Support for multiple means to download images including trust & image verification.
  • Container image management (managing image layers, overlay filesystems, etc).
  • Full management of container lifecycle
  • Support for pods to manage groups of containers together
  • Resource isolation of containers and pods.

What is not in scope for this project?

  • Signing and pushing images to various image storages. See Skopeo.
  • Container Runtimes daemons for working with Kubernetes CRIs. See CRI-O. We are working to integrate libpod into CRI-O to share containers and backend code with Podman.

OCI Projects Plans

The plan is to use OCI projects and best of breed libraries for different aspects:

  • Runtime: runc (or any OCI compliant runtime) and oci runtime tools to generate the spec
  • Images: Image management using containers/image
  • Storage: Container and image storage is managed by containers/storage
  • Networking: Networking support through use of CNI
  • Builds: Builds are supported via Buildah.
  • Conmon: Conmon is a tool for monitoring OCI runtimes. It is part of the CRI-O package

Podman Information for Developers

For blogs, release announcements and more, please checkout the website!

Installation notes Information on how to install Podman in your environment.

OCI Hooks Support Information on how Podman configures OCI Hooks to run when launching a container.

Podman API Documentation on the Podman API using Varlink.

Podman Commands A list of the Podman commands with links to their man pages and in many cases videos showing the commands in use.

Podman Troubleshooting Guide A list of common issues and solutions for Podman.

Podman Usage Transfer Useful information for ops and dev transfer as it relates to infrastructure that utilizes Podman. This page includes tables showing Docker commands and their Podman equivalent commands.

Tutorials Tutorials on using Podman.

Release Notes Release notes for recent Podman versions

Contributing Information about contributing to this project.

Current Roadmap

  1. Python frontend for Varlink API
  2. Integrate libpod into CRI-O to replace its existing container management backend
  3. Further work on the podman pod command
  4. Further improvements on rootless containers
  5. In-memory locking to replace file locks

Buildah and Podman relationship

Buildah and Podman are two complementary Open-source projects that are available on most Linux platforms and both projects reside at with Buildah (GitHub) and Podman (GitHub). Both Buildah and Podman are command line tools that work on OCI images and containers. The two projects differentiate in their specialization.

Buildah specializes in building OCI images. Buildah's commands replicate all of the commands that are found in a Dockerfile. Buildah’s goal is also to provide a lower level coreutils interface to build images, allowing people to build containers without requiring a Dockerfile. The intent with Buildah is to allow other scripting languages to build container images, without requiring a daemon.

Podman specializes in all of the commands and functions that help you to maintain and modify OCI images, such as pulling and tagging. It also allows you to create, run, and maintain those containers created from those images.

A major difference between Podman and Buildah is their concept of a container. Podman allows users to create "traditional containers" where the intent of these containers is to be long lived. While Buildah containers are really just created to allow content to be added back to the container image. An easy way to think of it is the buildah run command emulates the RUN command in a Dockerfile while the podman run command emulates the docker run command in functionality. Because of this and their underlying storage differences, you can not see Podman containers from within Buildah or vice versa.

In short Buildah is an efficient way to create OCI images while Podman allows you to manage and maintain those images and containers in a production environment using familiar container cli commands. For more details, see the Container Tools Guide.