Technology · Ebook

composefs: Verified, Deduplicated Filesystems

by Shriira Press

A practical, in-depth guide to composefs, the open-source Linux technology for content-addressed, integrity-verified, deduplicated read-only filesystem images. Learn how composefs makes images lean and tamper-proof: the filesystem image problem (duplication, slow extraction, missing integrity), content-addressed storage and deduplication, the composefs architecture (an EROFS metadata image plus a shared objects store, composed via overlayfs), fs-verity and end-to-end integrity (sealed images, a root of trust), mounting images directly (no extraction, lazy content, density), building images (mkcomposefs, digests, sealing), use cases (container storage, OSTree/bootc, immutable OSes, trusted boot), operations/security/best practices, and composefs in practice.

Contents

1. 1Preface
2. 2Chapter 1 — What composefs Is
3. 3Chapter 2 — The Filesystem Image Problem
4. 4Chapter 3 — Content-Addressed Storage and Deduplication
5. 5Chapter 4 — The composefs Architecture
6. 6Chapter 5 — fs-verity and Integrity
7. 7Chapter 6 — Mounting composefs Images
8. 8Chapter 7 — Building composefs Images
9. 9Chapter 8 — Use Cases: Containers, OSTree, and Bootable Systems
10. 10Chapter 9 — Operations, Security, and Best Practices
11. 11Chapter 10 — composefs in Practice