runtime.md
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# <a name="runtimeAndLifecycle" />Runtime and Lifecycle
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## <a name="runtimeScopeContainer" />Scope of a Container
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The entity using a runtime to create a container MUST be able to use the operations defined in this specification against that same container.
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Whether other entities using the same, or other, instance of the runtime can see that container is out of scope of this specification.
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## <a name="runtimeState" />State
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The state of a container includes the following properties:
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* **`ociVersion`** (string, REQUIRED) is the OCI specification version used when creating the container.
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* **`id`** (string, REQUIRED) is the container's ID.
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This MUST be unique across all containers on this host.
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There is no requirement that it be unique across hosts.
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* **`status`** (string, REQUIRED) is the runtime state of the container.
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The value MAY be one of:
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* `creating`: the container is being created (step 2 in the [lifecycle](#lifecycle))
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* `created`: the runtime has finished the [create operation](#create) (after step 2 in the [lifecycle](#lifecycle)), and the container process has neither exited nor executed the user-specified program
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* `running`: the container process has executed the user-specified program but has not exited (after step 5 in the [lifecycle](#lifecycle))
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* `stopped`: the container process has exited (step 7 in the [lifecycle](#lifecycle))
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Additional values MAY be defined by the runtime, however, they MUST be used to represent new runtime states not defined above.
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* **`pid`** (int, REQUIRED when `status` is `created` or `running` on Linux, OPTIONAL on other platforms) is the ID of the container process, as seen by the host.
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* **`bundle`** (string, REQUIRED) is the absolute path to the container's bundle directory.
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This is provided so that consumers can find the container's configuration and root filesystem on the host.
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* **`annotations`** (map, OPTIONAL) contains the list of annotations associated with the container.
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If no annotations were provided then this property MAY either be absent or an empty map.
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The state MAY include additional properties.
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When serialized in JSON, the format MUST adhere to the following pattern:
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```json
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{
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"ociVersion": "0.2.0",
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"id": "oci-container1",
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"status": "running",
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"pid": 4422,
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"bundle": "/containers/redis",
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"annotations": {
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"myKey": "myValue"
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}
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See [Query State](#query-state) for information on retrieving the state of a container.
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## <a name="runtimeLifecycle" />Lifecycle
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The lifecycle describes the timeline of events that happen from when a container is created to when it ceases to exist.
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1. OCI compliant runtime's [`create`](runtime.md#create) command is invoked with a reference to the location of the bundle and a unique identifier.
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2. The container's runtime environment MUST be created according to the configuration in [`config.json`](config.md).
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If the runtime is unable to create the environment specified in the [`config.json`](config.md), it MUST [generate an error](#errors).
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While the resources requested in the [`config.json`](config.md) MUST be created, the user-specified program (from [`process`](config.md#process)) MUST NOT be run at this time.
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Any updates to [`config.json`](config.md) after this step MUST NOT affect the container.
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3. Runtime's [`start`](runtime.md#start) command is invoked with the unique identifier of the container.
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4. The [prestart hooks](config.md#prestart) MUST be invoked by the runtime.
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If any prestart hook fails, the runtime MUST [generate an error](#errors), stop the container, and continue the lifecycle at step 9.
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5. The runtime MUST run the user-specified program, as specified by [`process`](config.md#process).
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6. The [poststart hooks](config.md#poststart) MUST be invoked by the runtime.
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If any poststart hook fails, the runtime MUST [log a warning](#warnings), but the remaining hooks and lifecycle continue as if the hook had succeeded.
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7. The container process exits.
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This MAY happen due to erroring out, exiting, crashing or the runtime's [`kill`](runtime.md#kill) operation being invoked.
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8. Runtime's [`delete`](runtime.md#delete) command is invoked with the unique identifier of the container.
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9. The container MUST be destroyed by undoing the steps performed during create phase (step 2).
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10. The [poststop hooks](config.md#poststop) MUST be invoked by the runtime.
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If any poststop hook fails, the runtime MUST [log a warning](#warnings), but the remaining hooks and lifecycle continue as if the hook had succeeded.
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## <a name="runtimeErrors" />Errors
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In cases where the specified operation generates an error, this specification does not mandate how, or even if, that error is returned or exposed to the user of an implementation.
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Unless otherwise stated, generating an error MUST leave the state of the environment as if the operation were never attempted - modulo any possible trivial ancillary changes such as logging.
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## <a name="runtimeWarnings" />Warnings
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In cases where the specified operation logs a warning, this specification does not mandate how, or even if, that warning is returned or exposed to the user of an implementation.
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Unless otherwise stated, logging a warning does not change the flow of the operation; it MUST continue as if the warning had not been logged.
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## <a name="runtimeOperations" />Operations
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Unless otherwise stated, runtimes MUST support the following operations.
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Note: these operations are not specifying any command-line APIs, and the parameters are inputs for general operations.
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### <a name="runtimeQueryState" />Query State
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`state <container-id>`
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This operation MUST [generate an error](#errors) if it is not provided the ID of a container.
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Attempting to query a container that does not exist MUST [generate an error](#errors).
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This operation MUST return the state of a container as specified in the [State](#state) section.
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### <a name="runtimeCreate" />Create
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`create <container-id> <path-to-bundle>`
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This operation MUST [generate an error](#errors) if it is not provided a path to the bundle and the container ID to associate with the container.
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If the ID provided is not unique across all containers within the scope of the runtime, or is not valid in any other way, the implementation MUST [generate an error](#errors) and a new container MUST NOT be created.
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This operation MUST create a new container.
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All of the properties configured in [`config.json`](config.md) except for [`process`](config.md#process) MUST be applied.
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[`process.args`](config.md#process) MUST NOT be applied until triggered by the [`start`](#start) operation.
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The remaining `process` properties MAY be applied by this operation.
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If the runtime cannot apply a property as specified in the [configuration](config.md), it MUST [generate an error](#errors) and a new container MUST NOT be created.
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The runtime MAY validate `config.json` against this spec, either generically or with respect to the local system capabilities, before creating the container ([step 2](#lifecycle)).
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Runtime callers who are interested in pre-create validation can run [bundle-validation tools](implementations.md#testing--tools) before invoking the create operation.
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Any changes made to the [`config.json`](config.md) file after this operation will not have an effect on the container.
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### <a name="runtimeStart" />Start
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`start <container-id>`
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This operation MUST [generate an error](#errors) if it is not provided the container ID.
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Attempting to `start` a container that is not [`created`](#state) MUST have no effect on the container and MUST [generate an error](#errors).
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This operation MUST run the user-specified program as specified by [`process`](config.md#process).
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This operation MUST generate an error if `process` was not set.
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### <a name="runtimeKill" />Kill
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`kill <container-id> <signal>`
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This operation MUST [generate an error](#errors) if it is not provided the container ID.
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Attempting to send a signal to a container that is neither [`created` nor `running`](#state) MUST have no effect on the container and MUST [generate an error](#errors).
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This operation MUST send the specified signal to the process in the container.
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### <a name="runtimeDelete" />Delete
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`delete <container-id>`
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This operation MUST [generate an error](#errors) if it is not provided the container ID.
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Attempting to `delete` a container that is not [`stopped`](#state) MUST have no effect on the container and MUST [generate an error](#errors).
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Deleting a container MUST delete the resources that were created during the `create` step.
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Note that resources associated with the container, but not created by this container, MUST NOT be deleted.
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Once a container is deleted its ID MAY be used by a subsequent container.
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## <a name="runtimeHooks" />Hooks
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Many of the operations specified in this specification have "hooks" that allow for additional actions to be taken before or after each operation.
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See [runtime configuration for hooks](./config.md#hooks) for more information.