Container

container-d

• K8s initially supports docker runtime only (cli,api,build, volumne, auth, security, runtime/container-d)
• Afterward supports different Runtime/s via CRI - OCI-standard imageSpec and ContainerSpec
• OCI - Open Container Interface.
• Any image follows OCI/imageSpec is supported by k8s
• Any Container follows OCI/ContainerSpec is support
• runtime:
  • rkt
  • docker ( supported via dockershim)
• v1.24
  • dockershim removed
  • docker is removed k8s
• so, container-d is runtime for docker as per OCI/ContainerSpec for kubernetes.
  • now standalone project under CNCF
  • needed only runtime, no other feature, then install it.

Command line

a. for container-d

• ctl - debug purpose , not user-friendly
• ctl image pull image1

• ctl run image1 c1-name

• nerdctl (advance/later)

• docker like CLI for container-d. can run all docker cmd.
• supports docker compose
• supports new feature/s:
  • encrypted image + image signing
  • lazy pulling
  • k8 namespace

b. For any CRI/OCI compatible container

• crictl
• CLI for any CRI/OCI compatible container
• install separately
• from k8 community
• special debugging purpose
• aware of pods.
• syntax quite similar