Durability
Storage and upgrades
What is disposable, what persists, and how Kern replaces a host safely.
Three storage lifetimes
ReplacedRoot volumeOS + host runtime
upgrade→recover→reconfigure
PreservedAdmin volumeDatabase + host state
PreservedAgent volumeagent-home + work
| Volume | Contains | Upgrade behavior |
|---|---|---|
| Root | OS, root-owned Kern runtime, installed system packages | Replaced during upgrade and reconfigure |
| Admin | Admin database and operator-controlled durable state | Detached and reattached |
| Agent | agent-home, repositories, artifacts, and agent-owned credentials | Detached and reattached |
Lifecycle semantics
- upgrade replaces the instance/root and preserves admin and agent data.
- recover creates a replacement host from preserved data when no instance exists.
- reconfigure replaces the root and operator endpoint configuration while preserving durable data.
- start and stop change runtime state without changing credentials, data, version, or endpoints.