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Signed-off-by: Eric Ernst <eric.ernst@intel.com>
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Eric Ernst 2018-05-09 15:00:22 -07:00
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architecture.md
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@ -30,7 +30,7 @@
## Overview ## Overview
This is an architectural overview of Kata Containers, based on the 1.0 release. This is an architectural overview of Kata Containers, based on the 1.0.0 release.
The two primary deliverables of the Kata Containers project are a container runtime The two primary deliverables of the Kata Containers project are a container runtime
and a CRI friendly library API. and a CRI friendly library API.
@ -50,13 +50,14 @@ and `kata-runtime`.
`kata-runtime` creates a QEMU\*/KVM virtual machine for each container or pod `kata-runtime` creates a QEMU\*/KVM virtual machine for each container or pod
the Docker engine or Kubernetes' `kubelet` creates. the Docker engine or Kubernetes' `kubelet` creates.
The container process is then spawned by an The container process is then spawned by
[agent](https://github.com/kata-containers/agent) running as a daemon inside [agent](https://github.com/kata-containers/agent), an agent process running
the virtual machine. The agent runs a gRPC server in the guest. This runs on a as a daemon inside the virtual machine. kata-agent runs a gRPC server in
virtio serial interface in the guest, and QEMU exposes them as a serial device on the guest using a virtio serial interface which QEMU exposes as a serial
the host. `kata-runtime` uses gRPC protocol the control device for sending container management device on the host. kata-runtime uses a gRPC protocol to communicate with
commands to the agent while the I/O serial device is used to pass I/O streams (`stdout`, `stderr`, the agent. This protocol allows the runtime to send container management
`stdin`) between the guest and the Docker Engine. commands to the agent. The protocol is also used to pass I/O streams (stdout,
stderr, stdin) between the guest and the Docker Engine.
For any given container, both the init process and all potentially executed For any given container, both the init process and all potentially executed
commands within that container, together with their related I/O streams, need commands within that container, together with their related I/O streams, need
@ -111,12 +112,12 @@ Each feature is documented below.
#### Machine accelerators #### Machine accelerators
Machine accelerators are architecture specific and can used to improve the performance Machine accelerators are architecture specific and can be used to improve the performance
and enable specific features of the machine types. The following machine accelerators and enable specific features of the machine types. The following machine accelerators
are used in Kata Containers: are used in Kata Containers:
- nvdimm: This machine accelerator is x86 specific and only supported by `pc` and - nvdimm: This machine accelerator is x86 specific and only supported by `pc` and
`q35` machine types. `nvdimm` is used to provide the root filesystem as persistent `q35` machine types. `nvdimm` is used to provide the root filesystem as a persistent
memory device to the Virtual Machine. memory device to the Virtual Machine.
Although Kata Containers can run with any recent QEMU release, Kata Containers Although Kata Containers can run with any recent QEMU release, Kata Containers
@ -166,7 +167,7 @@ has a highly optimized boot path.
The only services running in the context of the mini O/S are the init daemon The only services running in the context of the mini O/S are the init daemon
(`systemd`) and the [Agent](#agent). The real workload the user wishes to run (`systemd`) and the [Agent](#agent). The real workload the user wishes to run
is created using libcontainer, creating a container in the same manner that is done is created using libcontainer, creating a container in the same manner that is done
via runc. by runc.
For example, when `docker run -ti ubuntu date` is run: For example, when `docker run -ti ubuntu date` is run: