Kata Containers

  • Virtual machines - bigger, slower with more isolation. Boot time of minutes.
  • Containers - quick, simple but less isolation

kata containers is a blending of the two. Security and isolation of virtual machines without the bloat of virtual machines.

It is a vm

How do you use Kata Containers

It looks like runc an OCI compatible runtime

runC is the universal container runtime

History

Before kata there was Intel Clear Containers

Traditional Containers

You have a host and a kernel. Your containers run within namespaces on that host. All good until somebody breaks out of a container - which you have access to all containers.

Traditional containers in a VM

A Vm within a VM with containers in it

Kata has lightweight virtual machines

Kata Containers

  • Every Container / Pod gets it’s own virtual machine
  • Container doesn’t know it is a vm - same deployment process

Architeture and Integrations

Components: * QEMU - KVM * Runtime (Kata Runtime) * Kernel - to sit inside VM * rootfs image - vm has to boot something (rootfs sets up the container) * Agent - work to happen: mount points, networks, memory resources and cgroups * Shim * Proxy

CRI-O and Kata

Kubelet -> CRI (Container Runtime Interface) -> CRI-o/ContainerD -> runc -> kata-runtime -> vm

Can choose which you want - if you don’t trust it run it in a kata container

Fairly seemless

Networking and Storage

Containers run at layer 3 but vm’s run at layer 2

Storage: * 9pfs (overlay) - easy to use network based file system with plan9 (just works) - default. Not a full POSIX unix filesystem. * Block devices (device mapper) - vm can find block device , map and mount to virtual machine (not going over network connection) * Network (ceph, gluster) - Network storage works as you expect

Overhead

  • 50MB per container
  • Boot in less than a second

Road Map

Primarily around security and isolation

Security, in container: seccomp Security, on host: cgroup isolation, more namespace isolation, root-less QEMU and SELinux policy

Source