# OverlayFS with Firecracker

til · 2026-10-04

TIL about OverlayFS while reading [E2B's post on scaling Firecracker](https://e2b.dev/blog/scaling-firecracker-using-overlayfs-to-save-disk-space).

Instead of copying a whole root filesystem for every VM, you can share a read-only base and give each VM its own writable layer. Changes go into that layer; the base stays unchanged.