Preload default images

[r2d4]

Is this a BUG REPORT or FEATURE REQUEST? (choose one): Feature request

• Decrease startup time by preloading the default images into minikube
• Minikube usable offline with no additional setup (provided you have downloaded minikube and the iso already)

gcr.io/google_containers/k8s-dns-sidecar-amd64         1.14.4              38bac66034a6        3 days ago          41.81 MB
gcr.io/google_containers/k8s-dns-kube-dns-amd64        1.14.4              a8e00546bcf3        3 days ago          49.38 MB
gcr.io/google_containers/k8s-dns-dnsmasq-nanny-amd64   1.14.4              f7f45b9cb733        3 days ago          41.41 MB
gcr.io/google-containers/kube-addon-manager            v6.4-beta.2         0a951668696f        2 weeks ago         79.23 MB
gcr.io/google_containers/kubernetes-dashboard-amd64    v1.6.1              71dfe833ce74        6 weeks ago         134.4 MB
gcr.io/google_containers/pause-amd64                   3.0                 99e59f495ffa        14 months ago       746.9 kB

Upper bound on total image size to cache (no compression/no shared layers): 347 MB
Current ISO Size: 91 MB

We could add a systemd unit that depends on docker.service similar to minikube-automount. It would untar an image bundle and then docker load each image.

[r2d4]

This might also be beneficial to @aaron-prindle as it might make the startup time more reliable (since it won't be dependent on the network)

[dlorenc]

Something like this sgtm. I think docker load can actually save multiple images at once, which might help it take advantage of shared layers if any exist.

[aaron-prindle]

SGTM. As it makes the binary so much larger, are we going to catch these images on an original minikube start (similar to the iso and localkube now?). We should probably also release the tars on our release page so that that users can download all of the components to run minikube w/o internet in the future.

[coolbrg]

Any idea on the implementation details?

We recently implemented similar feature in minishift here.
Once the provisioning is done, we are running a background process to export the container images to minishift homedir.

[r2d4]

@budhrg See #1671 for my first draft

[r2d4]

Fixed by #1881