containersisolated

Containersisolated is a term used to describe the degree to which a software container's runtime environment isolates its processes, filesystem, network, and resources from the host system and from other containers. It combines kernel features, container runtimes, and orchestration configurations to limit interference and information leakage.

Key mechanisms include Linux namespaces (PID, IPC, NET, MNT, UTS, USER) that isolate process trees, network stacks, and mounted filesystems; control groups (cgroups) that limit CPU, memory, and I/O; and filesystem isolation via image layering and read-only roots. Additional layers are security profiles such as seccomp to constrain system calls, and Linux security modules like AppArmor or SELinux to enforce access controls.

User namespaces can map container root to non-privileged host users to reduce risk of privilege escalation; rootless containers enhance isolation by running without privileged privileges. Container runtimes (Docker, containerd, CRI-O, Podman) implement these features, often combined with container image formats and storage drivers, to create isolated execution environments. Orchestrators (Kubernetes, etc.) add network policies, pod isolation, and resource quotas to scale isolation across many containers.

Compared with traditional VMs, container isolation provides lower overhead but shares the host kernel, which means some kernel-level vulnerabilities can impact multiple containers. Isolation can be compromised by misconfigurations, privilege escalations, or insecure images. Regular updates, minimal base images, and careful privilege management are essential.

Best practices include dropping unnecessary capabilities, running containers as non-root users, using read-only root filesystems, applying seccomp profiles and AppArmor/SELinux policies, and enforcing resource quotas. Network isolation through firewalls or policies, and image provenance controls help maintain strong isolation in production.

See also: container security, namespaces, cgroups, seccomp, AppArmor, SELinux, rootless containers, Kubernetes, Docker, Podman.