ctr and crictl

Developing with Akri, it’s useful to be able to purge container images because, once cached, if changed, these are pulled by tag rather than hash.

The way to enumerate images used by MicroK8s is using either ctr or crictl. I’m unfamiliar with both of these but, here’s what I know:

  • crictl – client for CRI
  • ctr – containerd CLI

MicroK8s

MicroK8s leverages both technologies.

Both require sudo

ctr is a sub-command of microk8s and uses --address for the socket

sudo microk8s ctr --address=unix:///var/snap/microk8s/common/run/containerd.sock
NAME:
   ctr - 
        __
  _____/ /______
 / ___/ __/ ___/
/ /__/ /_/ /
\___/\__/_/

containerd CLI

And:

crictl is standalone and uses --runtime-endpoint for the socket.

sudo crictl --runtime-endpoint=unix:///var/snap/microk8s/common/run/containerd.sock
NAME:
   crictl - client for CRI

Both support images

The latter has ps and rmi