What is libcontainer?

Libcontainer is a tool that lets you create and manage Linux containers, self-contained execution environments that share the host system's core (the kernel) but are isolated from other containers and the host itself. Think of it as a way to run programs in their own sandboxed space, with control over what they can see and do, without needing a full separate operating system. At a high level, the project provides a Go library that handles the mechanics of setting up containers using Linux features like namespaces (which control what resources a container can see), cgroups (which limit how much CPU, memory, and other resources it can use), capabilities (which determine what system-level actions are allowed), and filesystem access controls. You configure a container with settings like its root filesystem, network setup, hostname, and resource limits, then start a process inside it. The library also lets you pause, resume, inspect running processes, gather stats, and destroy containers when you're done. The project includes a command-line tool called nsinit that demonstrates the library in action. You set up a directory with a Linux root filesystem and a configuration file, then run commands inside the container. If the main process dies, everything else in the container gets cleaned up automatically. The primary audience is developers building container tooling who need direct, programmatic control over how containers are created and managed, rather than relying on a higher-level tool that abstracts those details away. For example, someone building a custom deployment platform or orchestration system might use this library to handle the low-level container lifecycle themselves. It was originally created by Docker, Inc. back in 2014 and is released under the Apache 2.0 license. One notable aspect is that it's written in Go as a native implementation, meaning it doesn't depend on external container runtimes written in other languages. The README doesn't go into detail about specific performance tradeoffs or design decisions beyond pointing to separate principles and guidelines documents for contributors and maintainers.