For supporting things like hooks and updates we need a way to define runtime state of the container. This can be used to pass information to hooks so that they know the runtime state of the container and also used to dynamically make changes to resource allocations by running an update command for the runtime and have it reconcile the changes against the container's current state and the update requested.

For the hooks usecase the state should contain information such as:

• pid of the container's process
• paths to the namespaces (linux)
• paths to the cgroups setup for the container

For supporting updates the state should container information such as:

• pid of the container's process
• cgroup paths
• container root path
• cgroup/resource information
• device nodes
• rlimits
• sysctls
• mounts

Some of this information would be duplicated from the initial container's config so it maybe worth it to look into embedding the original config into the state structure.