Instances
One running container on one node.
An instance is one container on one node. Deployments create and replace them for you, or you start one yourself for a migration, a shell or a quick check that an image boots.
Isolation
On bare metal with KVM, each instance gets its own Firecracker microVM and guest kernel. Strong enough for sandboxes and untrusted code. On a cheap VPS or a VM inside a public cloud there's no KVM to use, so instances run as regular containers. Your config doesn't change.
The same two instances on two kinds of node. On bare metal with KVM, each runs in its own Firecracker microVM with its own guest kernel. On a VPS or cloud VM, they run as containers sharing the host kernel.
Lifecycle
An instance starts provisioning, then runs. It ends either exited, after a clean or requested stop, or failed, after a pull error or a non-zero exit. Only failed counts toward the deployment's backoff.
Things to know
- Instances don't move. Placement happens once. Moving means a new instance replaces it.
- Standalone instances aren't managed. One you start yourself, from the dashboard or with
unisrv instance run, won't come back if it dies, andunisrv upleaves it alone. - The filesystem is scratch. Mount a volume for anything that must outlive the instance.