* Both Flatcar Linux and Fedora CoreOS use systemd-resolved,
but they setup /etc/resolv.conf symlinks differently
* Prefer using /run/systemd/resolve/resolv.conf directly, which
also updates to reflect runtime changes (e.g. resolvectl)
* Change `enable_aggregation` default from false to true
* These days, Kubernetes control plane components emit annoying
messages related to assumptions baked into the Kubernetes API
Aggregation Layer if you don't enable it. Further the conformance
tests force you to remember to enable it if you care about passing
those
* This change is motivated by eliminating annoyances, rather than
any enthusiasm for Kubernetes' aggregation features
Rel: https://kubernetes.io/docs/concepts/extend-kubernetes/api-extension/apiserver-aggregation/
* Mount both /etc/ssl/certs and /etc/pki into control plane static
pods and kube-proxy, rather than choosing one based a variable
(set based on Flatcar Linux or Fedora CoreOS)
* Remove deprecated `--port` from `kube-scheduler` static Pod
* Update `null` provider to allow use of v3.1.x releases,
instead of being stuck on v2.1.2
* Update min versions in terraform-render-boostrap
https://github.com/poseidon/terraform-render-bootstrap/pull/287
* Document the recommended versions of Terraform cloud providers
* Remove `/sys/fs/cgroup/systemd` mount since Flatcar Linux
uses cgroups v2
* Flatcar Linux's `docker` switched from the `cgroupfs` to
`systemd` driver without notice
* Kubernetes v1.22.0 disabled kube-controller-manager insecure
port, which was used internally for Prometheus metrics scraping
* Configure Prometheus to discover and scrape endpoints for
kube-scheduler and kube-controller-manager via the authenticated
https ports, via bearer token
* Change firewall ports to allow Prometheus (on worker nodes)
to scrape kube-scheduler and kube-controller-manager targets
that run on controller(s) with hostNetwork
* Disable the insecure port on kube-scheduler
* On Fedora CoreOS, Cilium cross-node service IP load balancing
stopped working for a time (first observable as CoreDNS pods
located on worker nodes not being able to reach the kubernetes
API service 10.3.0.1). This turned out to have two parts:
* Fedora CoreOS switched to cgroups v2 by default. In our early
testing with cgroups v2, Calico (default) was used. With the
cgroups v2 change, SELinux policy denied some eBPF operations.
Since fixed in all Fedora CoreOS channels
* Cilium requires new mounts to support cgroups v2, which are
added here
* https://github.com/coreos/fedora-coreos-tracker/issues/292
* https://github.com/coreos/fedora-coreos-tracker/issues/881
* https://github.com/cilium/cilium/pull/16259
* Fedora CoreOS is beginning to switch from cgroups v1 to
cgroups v2 by default, which changes the sysfs hierarchy
* This will be needed when using a Fedora Coreos OS image
that enables cgroups v2 (`next` stream as of this writing)
Rel: https://github.com/coreos/fedora-coreos-tracker/issues/292
* Add `node_taints` variable to worker modules to set custom
initial node taints on cloud platforms that support auto-scaling
worker pools of heterogeneous nodes (i.e. AWS, Azure, GCP)
* Worker pools could use custom `node_labels` to allowed workloads
to select among differentiated nodes, while custom `node_taints`
allows a worker pool's nodes to be tainted as special to prevent
scheduling, except by workloads that explicitly tolerate the
taint
* Expose `daemonset_tolerations` in AWS, Azure, and GCP kubernetes
cluster modules, to determine whether `kube-system` components
should tolerate the custom taint (advanced use covered in docs)
Rel: #550, #663Closes#429
* Change control plane static pods to mount `/etc/kubernetes/pki`,
instead of `/etc/kubernetes/bootstrap-secrets` to better reflect
their purpose and match some loose conventions upstream
* Place control plane and bootstrap TLS assets and kubeconfig's
in `/etc/kubernetes/pki`
* Mount to `/etc/kubernetes/pki` (rather than `/etc/kubernetes/secrets`)
to match the host location (less surprise)
Rel: https://github.com/poseidon/terraform-render-bootstrap/pull/233
* Generate TLS client certificates for `kube-scheduler` and
`kube-controller-manager` with `system:kube-scheduler` and
`system:kube-controller-manager` CNs
* Template separate kubeconfigs for kube-scheduler and
kube-controller manager (`scheduler.conf` and
`controller-manager.conf`). Rename admin for clarity
* Before v1.16.0, Typhoon scheduled a self-hosted control
plane, which allowed the steady-state kube-scheduler and
kube-controller-manager to use a scoped ServiceAccount.
With a static pod control plane, separate CN TLS client
certificates are the nearest equiv.
* https://kubernetes.io/docs/setup/best-practices/certificates/
* Remove unused Kubelet certificate, TLS bootstrap is used
instead
* Allow terraform-provider-ct versions v0.6+ (e.g. v0.7.1)
Before, only v0.6.x point updates were allowed
* Update terraform-provider-ct to v0.7.1 in docs
* READ the docs before updating terraform-provider-ct,
as changing worker user-data is handled differently
by different cloud platforms
* Mark `kubeconfig` and `asset_dist` as `sensitive` to
prevent the Terraform CLI displaying these values, esp.
for CI systems
* In particular, external tools or tfvars style uses (not
recommended) reportedly display all outputs and are improved
by setting sensitive
* For Terraform v0.14, outputs referencing sensitive fields
must also be annotated as sensitive
Closes https://github.com/poseidon/typhoon/issues/884
* Allow a snippet with a systemd dropin to set an alternate
image via `ETCD_IMAGE`, for consistency across Fedora CoreOS
and Flatcar Linux
* Drop comments about integrating system containers with
systemd-notify
* CoreOS Container Linux was deprecated in v1.18.3
* Continue transitioning docs and modules from supporting
both CoreOS and Flatcar "variants" of Container Linux to
now supporting Flatcar Linux and equivalents
Action Required: Update the Flatcar Linux modules `source`
to replace `s/container-linux/flatcar-linux`. See docs for
examples
* On cloud platforms, `delete-node.service` tries to delete the
local node (not always possible depending on preemption time)
* Since v1.18.3, kubelet TLS bootstrap generates a kubeconfig
in `/var/lib/kubelet` which should be used with kubectl in
the delete-node oneshot
* Use docker to run the `kubelet.service` container
* Update Kubelet mounts to match Fedora CoreOS
* Remove unused `/etc/ssl/certs` mount (see
https://github.com/poseidon/typhoon/pull/810)
* Remove unused `/usr/share/ca-certificates` mount
* Remove `/etc/resolv.conf` mount, Docker default is ok
* Change `delete-node.service` to use docker instead of rkt
and inline ExecStart, as was done on Fedora CoreOS
* Fix permission denied on shutdown `delete-node`, caused
by the kubeconfig mount changing with the introduction of
node TLS bootstrap
Background
* podmand, rkt, and runc daemonless container process runners
provide advantages over the docker daemon for system containers.
Docker requires workarounds for use in systemd units where the
ExecStart must tail logs so systemd can monitor the daemonized
container. https://github.com/moby/moby/issues/6791
* Why switch then? On Flatcar Linux, podman isn't shipped. rkt
works, but isn't developing while container standards continue
to move forward. Typhoon has used runc for the Kubelet runner
before in Fedora Atomic, but its more low-level. So we're left
with Docker, which is less than ideal, but shipped in Flatcar
* Flatcar Linux appears to be shifting system components to
use docker, which does provide some limited guards against
breakages (e.g. Flatcar cannot enable docker live restore)
* Originally, poseidon/terraform-render-bootstrap generated
TLS certificates, manifests, and cluster "assets" written
to local disk (`asset_dir`) during terraform apply cluster
bootstrap
* Typhoon v1.17.0 introduced bootstrapping using only Terraform
state to store cluster assets, to avoid ever writing sensitive
materials to disk and improve automated use-cases. `asset_dir`
was changed to optional and defaulted to "" (no writes)
* Typhoon v1.18.0 deprecated the `asset_dir` variable, removed
docs, and announced it would be deleted in future.
* Add Terraform output `assets_dir` map
* Remove the `asset_dir` variable
Cluster assets are now stored in Terraform state only. For those
who wish to write those assets to local files, this is possible
doing so explicitly.
```
resource local_file "assets" {
for_each = module.yavin.assets_dist
filename = "some-assets/${each.key}"
content = each.value
}
```
Related:
* https://github.com/poseidon/typhoon/pull/595
* https://github.com/poseidon/typhoon/pull/678
* CoreOS Container Linux was deprecated in v1.18.3 (May 2020)
in favor of Fedora CoreOS and Flatcar Linux. CoreOS Container
Linux references were kept to give folks more time to migrate,
but AMIs have now been deleted. Time is up.
Rel: https://coreos.com/os/eol/
* seccomp graduated to GA in Kubernetes v1.19. Support for
seccomp alpha annotations will be removed in v1.22
* Replace seccomp annotations with the GA seccompProfile
field in the PodTemplate securityContext
* Switch profile from `docker/default` to `runtime/default`
(no effective change, since docker is the runtime)
* Verify with docker inspect SecurityOpt. Without the profile,
you'd see `seccomp=unconfined`
Related: https://github.com/poseidon/terraform-render-bootstrap/pull/215
* Fix race condition for bootstrap-secrets SELinux context on non-bootstrap controllers in multi-controller FCOS clusters
* On first boot from disk on non-bootstrap controllers, adding bootstrap-secrets races with kubelet.service starting, which can cause the secrets assets to have the wrong label until kubelet.service restarts (service, reboot, auto-update)
* This can manifest as `kube-apiserver`, `kube-controller-manager`, and `kube-scheduler` pods crashlooping on spare controllers on first cluster creation
* Fedora CoreOS now ships systemd-udev's `default.link` while
Flannel relies on being able to pick its own MAC address for
the `flannel.1` link for tunneled traffic to reach cni0 on
the destination side, without being dropped
* This change first appeared in FCOS testing-devel 32.20200624.20.1
and is the behavior going forward in FCOS since it was added
to align FCOS network naming / configs with the rest of Fedora
and address issues related to the default being missing
* Flatcar Linux (and Container Linux) has a specific flannel.link
configuration builtin, so it was not affected
* https://github.com/coreos/fedora-coreos-tracker/issues/574#issuecomment-665487296
Note: Typhoon's recommended and default CNI provider is Calico,
unless `networking` is set to flannel directly.
* In v1.18.3, the `os_stream` variable was added to select
a Fedora CoreOS image stream (stable, testing, next) on
AWS and Google Cloud (which publish official streams)
* Remove `os_image` variable deprecated in v1.18.3. Manually
uploaded images are no longer needed
* Accept experimental CNI `networking` mode "cilium"
* Run Cilium v1.8.0-rc4 with overlay vxlan tunnels and a
minimal set of features. We're interested in:
* IPAM: Divide pod_cidr into /24 subnets per node
* CNI networking pod-to-pod, pod-to-external
* BPF masquerade
* NetworkPolicy as defined by Kubernetes (no L7 Policy)
* Continue using kube-proxy with Cilium probe mode
* Firewall changes:
* Require UDP 8472 for vxlan (Linux kernel default) between nodes
* Optional ICMP echo(8) between nodes for host reachability
(health)
* Optional TCP 4240 between nodes for endpoint reachability (health)
Known Issues:
* Containers with `hostPort` don't listen on all host addresses,
these workloads must use `hostNetwork` for now
https://github.com/cilium/cilium/issues/12116
* Erroneous warning on Fedora CoreOS
https://github.com/cilium/cilium/issues/10256
Note: This is experimental. It is not listed in docs and may be
changed or removed without a deprecation notice
Related:
* https://github.com/poseidon/terraform-render-bootstrap/pull/192
* https://github.com/cilium/cilium/issues/12217
* Remove node label `node.kubernetes.io/master` from controller nodes
* Use `node.kubernetes.io/controller` (present since v1.9.5,
[#160](https://github.com/poseidon/typhoon/pull/160)) to node select controllers
* Rename controller NoSchedule taint from `node-role.kubernetes.io/master` to
`node-role.kubernetes.io/controller`
* Tolerate the new taint name for workloads that may run on controller nodes
and stop tolerating `node-role.kubernetes.io/master` taint
* Kubelet `--lock-file` and `--exit-on-lock-contention` date
back to usage of bootkube and at one point running Kubelet
in a "self-hosted" style whereby an on-host Kubelet (rkt)
started pods, but then a Kubelet DaemonSet was scheduled
and able to take over (hence self-hosted). `lock-file` and
`exit-on-lock-contention` flags supported this pivot. The
pattern has been out of favor (in bootkube too) for years
because of dueling Kubelet complexity
* Typhoon runs Kubelet as a container via an on-host systemd
unit using podman (Fedora CoreOS) or rkt (Flatcar Linux). In
fact, Typhoon no longer uses bootkube or control plane pivot
(let alone Kubelet pivot) and uses static pods since v1.16.0
* https://github.com/poseidon/typhoon/pull/536
* Generated Kubelet TLS certificate and key are not longer
used or distributed to machines since Kubelet TLS bootstrap
is used instead. Remove the certificate and key from state
* Enable terraform-provider-ct `strict` mode for parsing
Container Linux Configs and snippets
* Fix Container Linux Config systemd unit syntax `enable`
(old) to `enabled`
* Align with Fedora CoreOS which uses strict mode already
* Build Kubelet container images internally and publish
to Quay and Dockerhub (new) as an alternative in case of
registry outage or breach
* Use our infra to provide single and multi-arch (default)
Kublet images for possible future use
* Docs: Show how to use alternative Kubelet images via
snippets and a systemd dropin (builds on #737)
Changes:
* Update docs with changes to Kubelet image building
* If you prefer to trust images built by Quay/Dockerhub,
automated image builds are still available with unique
tags (albeit with some limitations):
* Quay automated builds are tagged `build-{short_sha}`
(limit: only amd64)
* Dockerhub automated builts are tagged `build-{tag}`
and `build-master` (limit: only amd64, no shas)
Links:
* Kubelet: https://github.com/poseidon/kubelet
* Docs: https://typhoon.psdn.io/topics/security/#container-images
* Registries:
* quay.io/poseidon/kubelet
* docker.io/psdn/kubelet
* Write the systemd kubelet.service to use `KUBELET_IMAGE`
as the Kubelet. This provides a nice way to use systemd
dropins to temporarily override the image (e.g. during a
registry outage)
Note: Only Typhoon Kubelet images and registries are supported.
* With Fedora CoreOS image stream support (#727), the latest
resolved image will change over the lifecycle of a cluster.
* Fix issue where an image diff proposed replacing a Fedora
CoreOS controller on GCP, introduced in #727 (unreleased)
* Also ignore image diffs to the GCP managed instance group
of workers. This aligns with worker AMI diffs being ignored
on AWS and similar on Azure, since workers update themselves.
Background:
* Controller nodes should strictly not be recreated by Terraform,
they are stateful (etcd) and should not be replaced
* Across cloud platforms, OS image diffs are ignored since both
Flatcar Linux and Fedora CoreOS nodes update themselves. For
workers, user-data or disk size diffs (where relevant) are allowed
to recreate workers templates/configs since these are considered
to be user-initiated declarations that a reprovision should be done
* Set a consistent MCS level/range for Calico install-cni
* Note: Rebooting a node was a workaround, because Kubelet
relabels /etc/kubernetes(/cni/net.d)
Background:
* On SELinux enforcing systems, the Calico CNI install-cni
container ran with default SELinux context and a random MCS
pair. install-cni places CNI configs by first creating a
temporary file and then moving them into place, which means
the file MCS categories depend on the containers SELinux
context.
* calico-node Pod restarts creates a new install-cni container
with a different MCS pair that cannot access the earlier
written file (it places configs every time), causing the
init container to error and calico-node to crash loop
* https://github.com/projectcalico/cni-plugin/issues/874
```
mv: inter-device move failed: '/calico.conf.tmp' to
'/host/etc/cni/net.d/10-calico.conflist'; unable to remove target:
Permission denied
Failed to mv files. This may be caused by selinux configuration on
the
host, or something else.
```
Note, this isn't a host SELinux configuration issue.
Related:
* https://github.com/poseidon/terraform-render-bootstrap/pull/186
* Enable bootstrap token authentication on kube-apiserver
* Generate the bootstrap.kubernetes.io/token Secret that
may be used as a bootstrap token
* Generate a bootstrap kubeconfig (with a bootstrap token)
to be securely distributed to nodes. Each Kubelet will use
the bootstrap kubeconfig to authenticate to kube-apiserver
as `system:bootstrappers` and send a node-unique CSR for
kube-controller-manager to automatically approve to issue
a Kubelet certificate and kubeconfig (expires in 72 hours)
* Add ClusterRoleBinding for bootstrap token subjects
(`system:bootstrappers`) to have the `system:node-bootstrapper`
ClusterRole
* Add ClusterRoleBinding for bootstrap token subjects
(`system:bootstrappers`) to have the csr nodeclient ClusterRole
* Add ClusterRoleBinding for bootstrap token subjects
(`system:bootstrappers`) to have the csr selfnodeclient ClusterRole
* Enable NodeRestriction admission controller to limit the
scope of Node or Pod objects a Kubelet can modify to those of
the node itself
* Ability for a Kubelet to delete its Node object is retained
as preemptible nodes or those in auto-scaling instance groups
need to be able to remove themselves on shutdown. This need
continues to have precedence over any risk of a node deleting
itself maliciously
Security notes:
1. Issued Kubelet certificates authenticate as user `system:node:NAME`
and group `system:nodes` and are limited in their authorization
to perform API operations by Node authorization and NodeRestriction
admission. Previously, a Kubelet's authorization was broader. This
is the primary security motivation.
2. The bootstrap kubeconfig credential has the same sensitivity
as the previous generated TLS client-certificate kubeconfig.
It must be distributed securely to nodes. Its compromise still
allows an attacker to obtain a Kubelet kubeconfig
3. Bootstrapping Kubelet kubeconfig's with a limited lifetime offers
a slight security improvement.
* An attacker who obtains the kubeconfig can likely obtain the
bootstrap kubeconfig as well, to obtain the ability to renew
their access
* A compromised bootstrap kubeconfig could plausibly be handled
by replacing the bootstrap token Secret, distributing the token
to new nodes, and expiration. Whereas a compromised TLS-client
certificate kubeconfig can't be revoked (no CRL). However,
replacing a bootstrap token can be impractical in real cluster
environments, so the limited lifetime is mostly a theoretical
benefit.
* Cluster CSR objects are visible via kubectl which is nice
4. Bootstrapping node-unique Kubelet kubeconfigs means Kubelet
clients have more identity information, which can improve the
utility of audits and future features
Rel: https://kubernetes.io/docs/reference/command-line-tools-reference/kubelet-tls-bootstrapping/
Rel: https://github.com/poseidon/terraform-render-bootstrap/pull/185
* Race: During initial bootstrap, static control plane pods
could hang with Permission denied to bootstrap secrets. A
manual fix involved restarting Kubelet, which relabeled mounts
The race had no effect on subsequent reboots.
* bootstrap.service runs podman with a private unshared mount
of /etc/kubernetes/bootstrap-secrets which uses an SELinux MCS
label with a category pair. However, bootstrap-secrets should
be shared as its mounted by Docker pods kube-apiserver,
kube-scheduler, and kube-controller-manager. Restarting Kubelet
was a manual fix because Kubelet relabels all /etc/kubernetes
* Fix bootstrap Pod to use the shared volume label, which leaves
bootstrap-secrets files with SELinux level s0 without MCS
* Also allow failed bootstrap.service to be re-applied. This was
missing on bare-metal and AWS
* In v1.18.0, kubectl apply would fail to apply manifests if any
single manifest was unable to validate. For example, if a CRD and
CR were defined in the same directory, apply would fail since the
CR would be invalid as the CRD wouldn't exist
* Typhoon temporary workaround was to separate CNI CRD manifests
and explicitly apply them first. No longer needed in v1.18.1+
* Kubernetes v1.18.1 restored the prior behavior where kubectl apply
applies as many valid manifests as it can. In the example above, the
CRD would be applied and the CR could be applied if the kubectl apply
was re-run (allowing for apply loops).
* Upstream fix: https://github.com/kubernetes/kubernetes/pull/89864
* No change to Fedora CoreOS modules
* For Container Linx AWS and Azure, change the `os_image` default
from coreos-stable to flatcar-stable
* For Container Linux GCP and DigitalOcean, change `os_image` to
be required since users should upload a Flatcar Linux image and
set the variable
* For Container Linux bare-metal, recommend users change the
`os_channel` to Flatcar Linux. No actual module change.
