Commit Graph

4 Commits

Author SHA1 Message Date
Dalton Hubble 0223b31e1a Ensure /etc/kubernetes exists following Kubelet inlining
* Inlining the Kubelet service removed the need for the
kubelet.env file declared in Ignition. However, on some
platforms, this removed the guarantee that /etc/kubernetes
exists. Bare-Metal and DigitalOcean distribute the kubelet
kubeconfig through Terraform file provisioner (scp) and
place it in (now missing) /etc/kubernetes
* https://github.com/poseidon/typhoon/pull/606
* Fix bare-metal and DigitalOcean Ignition to ensure the
desired directory exists following first boot from disk
* Cloud platforms with worker pools distribute the kubeconfig
through Ignition user data (no impact or need)
2020-01-06 21:38:20 -08:00
Dalton Hubble b2eb3e05d0 Disable Kubelet 127.0.0.1.10248 healthz endpoint
* Kubelet runs a healthz server listening on 127.0.0.1:10248
by default. Its unused by Typhoon and can be disabled
* https://kubernetes.io/docs/reference/command-line-tools-reference/kubelet/
2019-12-29 11:23:25 -08:00
Dalton Hubble f1f4cd6fc0 Inline Container Linux kubelet.service, deprecate kubelet-wrapper
* Change kubelet.service on Container Linux nodes to ExecStart Kubelet
inline to replace the use of the host OS kubelet-wrapper script
* Express rkt run flags and volume mounts in a clear, uniform way to
make the Kubelet service easier to audit, manage, and understand
* Eliminate reliance on a Container Linux kubelet-wrapper script
* Typhoon for Fedora CoreOS developed a kubelet.service that similarly
uses an inline ExecStart (except with podman instead of rkt) and a
more minimal set of volume mounts. Adopt the volume improvements:
  * Change Kubelet /etc/kubernetes volume to read-only
  * Change Kubelet /etc/resolv.conf volume to read-only
  * Remove unneeded /var/lib/cni volume mount

Background:

* kubelet-wrapper was added in CoreOS around the time of Kubernetes v1.0
to simplify running a CoreOS-built hyperkube ACI image via rkt-fly. The
script defaults are no longer ideal (e.g. rkt's notion of trust dates
back to quay.io ACI image serving and signing, which informed the OCI
standard images we use today, though they still lack rkt's signing ideas).
* Shipping kubelet-wrapper was regretted at CoreOS, but remains in the
distro for compatibility. The script is not updated to track hyperkube
changes, but it is stable and kubelet.env overrides bridge most gaps
* Typhoon Container Linux nodes have used kubelet-wrapper to rkt/rkt-fly
run the Kubelet via the official k8s.gcr.io hyperkube image using overrides
(new image registry, new image format, restart handling, new mounts, new
entrypoint in v1.17).
* Observation: Most of what it takes to run a Kubelet container is defined
in Typhoon, not in kubelet-wrapper. The wrapper's value is now undermined
by having to workaround its dated defaults. Typhoon may be better served
defining Kubelet.service explicitly
* Typhoon for Fedora CoreOS developed a kubelet.service without the use
of a host OS kubelet-wrapper which is both clearer and eliminated some
volume mounts
2019-12-29 11:17:26 -08:00
Dalton Hubble 50db3d0231 Rename CLC files and favor Terraform list index syntax
* Rename Container Linux Config (CLC) files to *.yaml to align
with Fedora CoreOS Config (FCC) files and for syntax highlighting
* Replace common uses of Terraform `element` (which wraps around)
with `list[index]` syntax to surface index errors
2019-12-28 12:14:01 -08:00