Container basics

Image manager

Downloads an image from the registry, unpacks layers (base OS, libs, etc.), merge via overlayfs, plus a writable top layer so the original image stays untouched.

Config (OCI spec)

A config.json describing the box: command to run, env vars, limits, mounts, which isolation to apply. Every other part reads from this.

Process creator

Starts the process inside new namespaces, so it gets its own view of processes, hostname, mounts, networks, and users.

Filesystem setup

Mounts /proc, /dev, /sys, then pivot_root into the merged image folder. After this, the process can’t see the host’s files at all.

Resource limits (groups v2)

Caps resources.

Security hardening

1. User namespace (root inside maps to a nobody outside)

2. Capabilities: drop root’s special powers

3. seccomp: block dangerous sys calls entirely

Networking

Virtual cable (veto) to a bridge with NAT, so the box can reach the internet. (default for agents is no network)

Init process

PID 1 inside the box has special duties: forward signals (so Ctrl+C works) and clean up zombie processes.

Lifecycle manager

Commands create / start / state / kill / delete, tracks which boxes exist, and cleans up mounts and cgroups even if something crashes.