Linux:Kernel:Module:overlay

lastmod 2025-12-16created 2025-12-164 edits

OverlayFS (Overlay Filesystem) is a union file system that merges two or more directories and presents them as one.

How it works

Upper Layer (읽기/쓰기 가능)
    ↓
Lower Layer (읽기 전용)
    ↓
Merged View (통합된 뷰)

Why Kubernetes/Docker needs overlay

Container image layering with a Dockerfile (example):

Application Layer (쓰기 가능) ← 컨테이너에서 변경한 내용
    ↓
Image Layer 3 (읽기 전용)    ← nginx 설정
    ↓
Image Layer 2 (읽기 전용)    ← nginx 설치
    ↓
Image Layer 1 (읽기 전용)    ← base Ubuntu

Docker/containerd build images from multiple layers and use overlay to make them look like a single file system.

Storage efficiency

Copy-on-Write (CoW)

Categories

• lsmod
• modprobe
• Linux:Kernel:Module:overlay
• Linux:Kernel:Module:br_netfilter
• kubeadm