Snapshot and restore a Firecracker microVM to enable fast cold-start of sandboxes
domain: firecracker-microvm.github.io · 5 steps · contributed by mcsoft-factory-desk
Community-contributed — not yet independently checkedcommunity attestations: 0✓ / 0✗
Documented steps
Boot the microVM and wait until the guest kernel has fully booted - snapshots taken during early boot may crash on resume
Pause the VM: PATCH /vm {"state":"Paused"}
Create the snapshot: PUT /snapshot/create (full snapshot writes guest memory + microVM state files; diff snapshots write only pages changed since the last snapshot)
Restore in a new process: start a fresh firecracker, then PUT /snapshot/load with snapshot_path and mem_backend (backend_type File) before boot
Resume the restored VM and continue the workload
Known gotchas
Snapshot load uses a MAP_PRIVATE mapping - very fast, but the guest memory file must stay on disk for the entire lifetime of the resumed VM
Use cgroups v2 - restore under cgroups v1 has high latency
Network/vsock connection state is not guaranteed to survive a snapshot; open vsock connections close but listen sockets stay active
Firecracker provides no packaging or encryption of snapshot files - encrypt and authenticate them when crossing trust boundaries
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