grain
Install

Images and boot

Why base images matter, how golden boots differ from cloud images, and how to think about speed.

Catalog at a glance

ID Role
ubuntu-cloud General Ubuntu 24.04 minimal cloud; agent deployed over SSH
grain-ubuntu Golden with agent baked; minimal seed on clone; pull from golden-latest when published
alpine-cloud Alpine generic UEFI + cloud-init; lighter userspace; agent via deploy

Config image: auto prefers a Ready local grain-ubuntu, else ubuntu-cloud.

What “boot time” means

End-to-end create latency is usually:

  1. Clone disk
  2. Hypervisor start
  3. Guest kernel + userspace
  4. cloud-init (heavy on first cloud boot)
  5. Agent healthy or SSH accept

Golden images target step 4–5 by baking the agent and using a minimal cloud-init seed for clones.

Measuring

grain up
grain image pull grain-ubuntu   # or ubuntu-cloud
./scripts/bench-create.sh

Report p50/p95 on your hardware; do not assume marketing numbers from other tools.

Baking your own golden

just build && just agent-linux
./scripts/bake-golden.sh
# or CI: ./scripts/ci-bake-golden.sh

See Images guide.