Runtimes#
The runtime is what actually executes the operator’s code, the layer between source and CPU. Bare metal under a sysadmin’s hands, virtual machines, containers, orchestrators, service meshes, and serverless platforms each ship a different bargain between control, isolation, and overhead.
The historical progression runs top-to-bottom in the toctree below. The operator will rarely meet one in isolation; modern estates stack them (containers in VMs in a cloud-managed orchestrator, talking through a service mesh) and the operator must be able to read each layer to attack, defend, or build on top of it.
Bare metal under a sysadmin’s hands. Where every layer above this one started.
Hypervisors, VMs, paravirtualisation. The first big jump in density and isolation.
How the runtime stack composes: kernel, namespace, cgroup, VM, hypervisor.
Process-level packaging with shared kernel. The unit modern pipelines ship.
Kubernetes, Nomad, Swarm. Scheduling, networking, and lifecycle across many hosts.
Sidecars and control planes. mTLS, retries, traffic shaping between services.
Function- and container-as-a-service. The runtime the operator never logs into.