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[Do Not Merge] Release 1.12 (#10292)

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* Update docs for fields allowed at root of CRD schema (#9973)

* add plugin docs and examples (#10053)

* docs update to promote TaintNodesByCondition to beta (#9626)

* HPA Specificity Improvements (#8757)

Updated the HPA docs to reference the `autoscaling/v2beta2` API version,
and added documentation about the new fields.

* adjust docs for pod ready++ (#10049)

* Remove --cadvisor-port - has been deprecated since v1.10 (#10023)

Change-Id: Id2a685473a243aef492a98ff450759f39e362557

* Add Documentation for Snapshot Feature (#9948)

* Add documentation for snapshot feature

* Update volume-snapshots.md

* Add dry-run to api-concepts (#10033)

* kubeadm-init: Update the offline support section (#10062)

The update includes the following things (in mind with Kubernetes 1.12):

- Remove the 1.8 image versions
- Add the 1.10 image versions that were missing until now
- Include a comment for the missing arch suffixes in 1.12

Signed-off-by: Rostislav M. Georgiev <rostislavg@vmware.com>

* Say bye to `DynamicProvisioningScheduling` (#10157)

The mentioned feature gate is now collapsed into `VolumeScheduling`.

xref: kubernetes/kubernetes#67432

* Update ResourceQuota per PriorityClass state for 1.12 (#10229)

* TokenRequest and TokenRequestProjection now beta (#10161)

xref: kubernetes/kubernetes#67349

* Change feature state for kms provider to beta. (#10230)

KMS Provider will be graduating to beta in v1.12, reflecting this change on the website.

* coredns default (#10200)

* Promote ShareProcessNamespace to beta in docs (#9996)

* Add CoreDNS details to DNS Debug docs (#10201)

* add coredns details

* address nits, add query logging section

* Update docs with topology aware dynamic provisioning (#9939)

* Document topology aware volume binding feature

* update for readability

* Update storage-classes.md

* comma splice

* don't abbreviate

* HPA Algorithm Information Improvements (#9780)

* Update HPA docs with more algorithm details

The HPA docs pointed to an out-of-date document for information on the
algorithm details, which users were finding confusing.  This sticks a
section on the algorithm in the HPA docs instead, documenting both
general behavior and corner cases.

* Add glossary info, HPA docs on quantities

People often ask about the quantity notation when working with the
metrics APIs, so this adds a glossary entry on quantities (since they're
used elsewhere in the system), and a short explantation in the HPA walkthough.

* Information about HPA readiness and stabilization

This adds information about the new changes to HPA readiness and
stabilization from kubernetes/features#591, and other minor changes that
landed in Kubernetes 1.12.

* Update horizontal-pod-autoscale.md

* Audit 1.12 doc (#9953)

* audit 1.12 document

* remove legacy audit feature

https://github.com/kubernetes/kubernetes/pull/65862

* update feature gate doc

* MountPropagation is now GA (#10090)

* RuntimeClass documentation (#10102)

* RuntimeClass documentation

* Update runtime-class.md

* Add documentation for Scheduler performance tuning (#10048)

* Add documentation for Scheduler performance tuning

* Update scheduler-perf-tuning.md

* TTL controller for cleaning up finished resources (#10064)

* TTL controller for cleaning up finished resources

* Address comments

* Update ttlafterfinished.md

* Bump quota configuration api version (#10217)

* Incremental update from master (#10278)

* fix invalid href of cloud controller manager (#10240)

* fix invalid yaml format (#10238)

* update storage-limits doc with Azure disk part (#10224)

update storage-limits doc with Azure disk part

fix comments

* Update kubelet-config-file.md (#10222)

Update link to KubeletConfiguration struct.

* fix a trivial misspelling (#10244)

* Fix cassandra-statefulset.yaml indent level (#10243)

* Mention minimum etcd versions (#10208)

Source: https://groups.google.com/d/msg/kubernetes-dev/jMPA4JzKiY4/HIx2ugvLBAAJ

* fix 404 error (#10250)

* Small verb tweak (#10190)

Present participle, ftw.

* Add AnchorJS logic for header links (#10155)

* Add AnchorJS JavaScript

* Remove existing inpage_heading logic

* Remove underline from anchor tags

* Use single icon and add touch visibility

* Use paragraph link icon for AnchorJS

* Update Sass to use code formatting in docsContent headers

* Update header size coverage to H3-H6

* fix broken link in kubefed.md (#10254)

* Update the version numbers for the X-Remote-Extra- and Impersonate-Extra- key fixes (#9827)

The fix was cherry picked into 1.11.3, 1.10.7, and 1.9.11:

https://github.com/kubernetes/kubernetes/pull/67162
https://github.com/kubernetes/kubernetes/pull/67163
https://github.com/kubernetes/kubernetes/pull/67164

* fix typo (#10168)

* fix typo

* addressing comments.

* Update setup-ha-etcd-with-kubeadm.md

* fix typos (#10252)

* fix description of contribute guide (#10253)

* describe truncate feature about advanced audit (#10236)

* describe truncate feature about advanced audit

* Update audit.md

* docs update to promote ScheduleDaemonSetPods to beta (#9923)

* Dynamic volume limit updates for 1.12 (#10211)

* add a placeholder commit

* Update docs for csi volume limits

* Update storage-limits.md

* Add "MayRunAs" value among other GroupStrategies (#9888)

* Add CoreDNS details to the customize DNS doc (#10228)

* Add CoreDNS details to the customize DNS doc

Rewrite the document to include more details about CoreDNS, since it's now the default from v1.12

* Address comments

* Improve doc wording

* Fix link

* Update dns-custom-nameservers.md

* Update dns-custom-nameservers.md

* Fix secrets docs in 1.12 branch (#10056)

* Fix secrets docs

* Update secret.md

* Revert CoreDNS Docs (#10319)

* Revert "Add CoreDNS details to DNS Debug docs (#10201)"

This reverts commit 462817a674.

* Revert "Add CoreDNS details to the customize DNS doc (#10228)"

This reverts commit e7319eeb8c.

* Revert "coredns default (#10200)"

This reverts commit 698e93b441.

* Add CRI installation instructions page

Added cri-installation page with CRI installation instructions
Referenced it from kubeadm-init and install-kubeadm pages.

* kubeadm: update API types documentation for 1.12 (#10283)

v1alpha2 -> v1alpha3
MasterConfiguration -> [new-api-types]

* TokenRequest feature documentation (#10295)

* AdvancedAuditing is now GA (#10156)

xref: kubernetes/kubernetes#65862

`AdvancedAuditing` feature is GA in 1.12. This PR adjusts the related
docs.

* update runtime-class.md (#10332)

* update runtime-class.md

* Update runtime-class.md

* Document cross-authorizer permissions for creating RBAC roles (#10015)

* Document cross-authorizer permissions for creating RBAC roles

* Update rbac.md

* kubeadm: update authored content for 1.12 (reference docs and cluster creation) (#10348)

* kubeadm: update authored content in reference docs for 1.12

* kubeadm: add time frame in create-cluster-kubeadm for 1.12

* add AllowedProcMountTypes and ProcMountType to docs (#9911)

Signed-off-by: Jess Frazelle <acidburn@microsoft.com>

* kubeadm: add new command line reference (#10306)

Add:
- placeholder files
- include place holder files
- include "renew" sub command
- add missing tabs for "alpha phase kubelet"

* Documenting SCTP support in Kubernetes (#10279)

* Documenting SCTP support in Kubernetes Service, Endpoint, NetworkPolicy and Pod

* Updates based on comments on the PR

* kubectl expose update with SCTP support

* Updated according to comments in the PR

* Revert "kubectl expose update with SCTP support"

This reverts commit 0d5a1e6720a012390cf100c83e16b4a8c0782356.

* TLS Bootstrap and Server Cert Rotation feature documentation (#10232)

* TokenRequest feature documentation

* line wrapping to make review not insane

* update content for GA without major refactor

* Update kubelet-tls-bootstrapping.md

* Add clarifications for volume snapshots (#10296)

* Update kubadm ha installation for 1.12 (#10264)

* Update kubadm ha installation for 1.12

Signed-off-by: Chuck Ha <ha.chuck@gmail.com>

* update stable version

Signed-off-by: Chuck Ha <ha.chuck@gmail.com>

* Update stacked control plane for v1.12 (#2)

* use v1alpha3

Signed-off-by: Chuck Ha <ha.chuck@gmail.com>

* more v1alpha3 (#4)

* updates

Signed-off-by: Chuck Ha <ha.chuck@gmail.com>

* Document how to run in-tree cloud providers with kubeadm (#10357)

Change-Id: Iab6b996a830503d74a6eb0c507c5f8ca7a39235b

* kubeadm reference doc for release 1.12 (#10359)

* Revert "Revert "Add CoreDNS details to DNS Debug docs (#10201)""

This reverts commit bb30f4d1fcd6fba2fe6190778ead99f8010033b7.

* Revert "Revert "Add CoreDNS details to the customize DNS doc (#10228)""

This reverts commit bc23d45c09d7b83cac130fe22a0bd91e72435862.

* Revert "Revert "coredns default (#10200)""

This reverts commit 7f4350d6ab7fc554ee53126d3875e845d2e43d1f.

* add missing instruction for ha guide (#10374)

Signed-off-by: Chuck Ha <ha.chuck@gmail.com>

* kubeadm - Ha upgrade updates (#10340)

* Update HA upgrade docs

* Adds external etcd HA upgrade guide

Signed-off-by: Chuck Ha <ha.chuck@gmail.com>

* copyedit

* more edits

* add runasgroup in psp (#10076)

* update KubeletPluginsWatcher feature gate (#10205)

* generated 1.12 docs

* Building Multi-arch images with Manifests (#10379)

In 1.12, a variety of images used in a typical kubernetes installation
have started to using manifests to better support environments with arm
or ppc64le architectures. For example all images used with kubeadm by
default have manifests, another would be all the tests in the
conformance test suite. Here we capture the best practices for everyone
to start using manifests in their own workflows.

Change-Id: I5ba4c5fe55ffc9486a8251760f3352be4f2e1494

* Upgrade docs for v1.12 (#10344)

* generated assets and docs

* remove 1.7

* update 1.12

* update plugin documentation under docs>tasks>extend-kubectl (#10259)

* update plugin documentation under docs>tasks>extend-kubectl

* Update kubectl-plugins.md
This commit is contained in:
Jim Angel
2018-09-27 18:41:39 -05:00
committed by k8s-ci-robot
parent 593b631522
commit 786d314da5
178 changed files with 9054 additions and 2728 deletions
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content/en/docs/reference/command-line-tools-reference/kubelet-tls-bootstrapping.md
+136 -91
View File
@@ -1,17 +1,20 @@
---
reviewers:
- ericchiang
- mikedanese
- jcbsmpsn
- liggitt
- smarterclayton
- awly
title: TLS bootstrapping
content_template: templates/concept
---
{{% capture overview %}}
This document describes how to set up TLS client certificate bootstrapping for kubelets.
Kubernetes 1.4 introduced an API for requesting certificates from a cluster-level Certificate Authority (CA). The original intent of this API is to enable provisioning of TLS client certificates for kubelets. The proposal can be found [here](https://github.com/kubernetes/kubernetes/pull/20439)
and progress on the feature is being tracked as [feature #43](https://github.com/kubernetes/features/issues/43).
This document describes how to set up TLS client certificate bootstrapping for
kubelets. Kubernetes 1.4 introduced an API for requesting certificates from a
cluster-level Certificate Authority (CA). The original intent of this API is to
enable provisioning of TLS client certificates for kubelets. The proposal can be
found [here](https://github.com/kubernetes/kubernetes/pull/20439).
{{% /capture %}}
@@ -19,53 +22,76 @@ and progress on the feature is being tracked as [feature #43](https://github.com
## kube-apiserver configuration
The API server should be configured with an [authenticator](/docs/reference/access-authn-authz/authentication/) that can authenticate tokens as a user in the `system:bootstrappers` group.
The API server should be configured with an
[authenticator](/docs/reference/access-authn-authz/authentication/) that can
authenticate tokens as a user in the `system:bootstrappers` group.
This group will later be used in the controller-manager configuration to scope approvals in the default approval
controller. As this feature matures, you should ensure tokens are bound to a Role-Based Access Control (RBAC) policy which limits requests
(using the bootstrap token) strictly to client requests related to certificate provisioning. With RBAC in place, scoping the tokens to a group allows for great flexibility (e.g. you could disable a particular bootstrap group's access when you are done provisioning the nodes).
This group will later be used in the controller-manager configuration to scope
approvals in the default approval controller. As this feature matures, you
should ensure tokens are bound to a Role Based Access Control (RBAC) policy
which limits requests (using the [bootstrap
token](/docs/reference/access-authn-authz/bootstrap-tokens/)) strictly to client
requests related to certificate provisioning. With RBAC in place, scoping the
tokens to a group allows for great flexibility (e.g. you could disable a
particular bootstrap group's access when you are done provisioning the nodes).
While any authentication strategy can be used for the kubelet's initial bootstrap credentials, the following two authenticators are recommended for ease of provisioning.
While any authentication strategy can be used for the kubelet's initial
bootstrap credentials, the following two authenticators are recommended for ease
of provisioning.
1. [Bootstrap Tokens](/docs/reference/access-authn-authz/bootstrap-tokens/) - __beta__
2. [Token authentication file](#token-authentication-file)
Using bootstrap tokens is currently __beta__ and will simplify the management of bootstrap token management especially in a HA scenario.
Using bootstrap tokens is currently __beta__ and will simplify the management of
bootstrap token management especially in a HA scenario.
### Token authentication file
Tokens are arbitrary but should represent at least 128 bits of entropy derived from a secure random number
generator (such as /dev/urandom on most modern systems). There are multiple ways you can generate a token. For example:
Tokens are arbitrary but should represent at least 128 bits of entropy derived
from a secure random number generator (such as /dev/urandom on most modern Linux
systems). There are multiple ways you can generate a token. For example:
```
head -c 16 /dev/urandom | od -An -t x | tr -d ' '
```
will generate tokens that look like `02b50b05283e98dd0fd71db496ef01e8`
will generate tokens that look like `02b50b05283e98dd0fd71db496ef01e8`.
The token file should look like the following example, where the first three values can be anything and the quoted group
name should be as depicted:
The token file should look like the following example, where the first three
values can be anything and the quoted group name should be as depicted:
```
02b50b05283e98dd0fd71db496ef01e8,kubelet-bootstrap,10001,"system:bootstrappers"
```
Add the `--token-auth-file=FILENAME` flag to the kube-apiserver command (in your systemd unit file perhaps) to enable the token file.
See docs [here](/docs/reference/access-authn-authz/authentication/#static-token-file) for further details.
Add the `--token-auth-file=FILENAME` flag to the kube-apiserver command (in your
systemd unit file perhaps) to enable the token file. See docs
[here](/docs/reference/access-authn-authz/authentication/#static-token-file) for
further details.
### Client certificate CA bundle
Add the `--client-ca-file=FILENAME` flag to the kube-apiserver command to enable client certificate authentication,
referencing a certificate authority bundle containing the signing certificate (e.g. `--client-ca-file=/var/lib/kubernetes/ca.pem`).
Add the `--client-ca-file=FILENAME` flag to the kube-apiserver command to enable
client certificate authentication, referencing a certificate authority bundle
containing the signing certificate (e.g.
`--client-ca-file=/var/lib/kubernetes/ca.pem`).
## kube-controller-manager configuration
The API for requesting certificates adds a certificate-issuing control loop to the Kubernetes Controller Manager. This takes the form of a
[cfssl](https://blog.cloudflare.com/introducing-cfssl/) local signer using assets on disk. Currently, all certificates issued have one year validity and a default set of key usages.
The API for requesting certificates adds a certificate-issuing control loop to
the Kubernetes Controller Manager. This takes the form of a
[cfssl](https://blog.cloudflare.com/introducing-cfssl/) local signer using
assets on disk. Currently, all certificates issued have one year validity and a
default set of key usages.
### Signing assets
You must provide a Certificate Authority in order to provide the cryptographic materials necessary to issue certificates.
This CA should be trusted by kube-apiserver for authentication with the `--client-ca-file=FILENAME` flag. The management
of the CA is beyond the scope of this document but it is recommended that you generate a dedicated CA for Kubernetes.
Both certificate and key are assumed to be PEM-encoded.
You must provide a Certificate Authority in order to provide the cryptographic
materials necessary to issue certificates. This CA should be trusted by
kube-apiserver for authentication with the `--client-ca-file=FILENAME` flag. The
management of the CA is beyond the scope of this document but it is recommended
that you generate a dedicated CA for Kubernetes. Both certificate and key are
assumed to be PEM-encoded.
The kube-controller-manager flags are:
@@ -73,31 +99,31 @@ The kube-controller-manager flags are:
--cluster-signing-cert-file="/etc/path/to/kubernetes/ca/ca.crt" --cluster-signing-key-file="/etc/path/to/kubernetes/ca/ca.key"
```
### Approval controller
The validity duration of signed certificates can be configured with flag:
In 1.7 the experimental "group auto approver" controller is dropped in favor of the new `csrapproving` controller
that ships as part of [kube-controller-manager](/docs/admin/kube-controller-manager/) and is enabled by default.
The controller uses the [`SubjectAccessReview` API](/docs/reference/access-authn-authz/authorization/#checking-api-access) to determine
if a given user is authorized to request a CSR, then approves based on the authorization outcome. To prevent
conflicts with other approvers, the builtin approver doesn't explicitly deny CSRs, only ignoring unauthorized requests.
```
--experimental-cluster-signing-duration
```
### SubjectAccessReview Approval Controller
The `csrapproving` controller that ships as part of
[kube-controller-manager](/docs/admin/kube-controller-manager/) and is enabled
by default. The controller uses the [`SubjectAccessReview`
API](/docs/reference/access-authn-authz/authorization/#checking-api-access) to
determine if a given user is authorized to request a CSR, then approves based on
the authorization outcome. To prevent conflicts with other approvers, the
builtin approver doesn't explicitly deny CSRs. It only ignores unauthorized
requests. The controller also prunes expired certificates as part of garbage
collection.
The controller categorizes CSRs into three subresources:
1. `nodeclient` - a request by a user for a client certificate with `O=system:nodes` and `CN=system:node:(node name)`.
2. `selfnodeclient` - a node renewing a client certificate with the same `O` and `CN`.
3. `selfnodeserver` - a node renewing a serving certificate. (ALPHA, requires feature gate)
2. `selfnodeclient` - a node renewing a client certificate with the same `O` and `CN`. A node can use its existing client certificate to authenticate this request.
The checks to determine if a CSR is a `selfnodeserver` request is currently tied to the kubelet's credential rotation
implementation, an __alpha__ feature. As such, the definition of `selfnodeserver` will likely change in a future and
requires the `RotateKubeletServerCertificate` feature gate on the controller manager. The feature progress can be
tracked at [kubernetes/features#267](https://github.com/kubernetes/features/issues/267).
```
--feature-gates=RotateKubeletServerCertificate=true
```
The following RBAC `ClusterRoles` represent the `nodeclient`, `selfnodeclient`, and `selfnodeserver` capabilities. Similar roles
may be automatically created in future releases.
The following RBAC `ClusterRoles` represent the `nodeclient` and
`selfnodeclient`, capabilities.
```yml
# A ClusterRole which instructs the CSR approver to approve a user requesting
@@ -121,36 +147,21 @@ rules:
- apiGroups: ["certificates.k8s.io"]
resources: ["certificatesigningrequests/selfnodeclient"]
verbs: ["create"]
---
# A ClusterRole which instructs the CSR approver to approve a node requesting a
# serving cert matching its client cert.
kind: ClusterRole
apiVersion: rbac.authorization.k8s.io/v1
metadata:
name: approve-node-server-renewal-csr
rules:
- apiGroups: ["certificates.k8s.io"]
resources: ["certificatesigningrequests/selfnodeserver"]
verbs: ["create"]
```
As of 1.8, equivalent roles to the ones listed above are automatically created as part of the default RBAC roles.
For 1.8 clusters admins are recommended to bind tokens to the following roles instead of creating their own:
As of 1.8, equivalent roles to the ones listed above are automatically created
as part of the default RBAC roles. For 1.8 clusters admins are recommended to
bind node bootstrap identities to the following roles instead of creating their
own:
* `system:certificates.k8s.io:certificatesigningrequests:nodeclient`
- Automatically approve CSRs for client certs bound to this role.
* `system:certificates.k8s.io:certificatesigningrequests:selfnodeclient`
- Automatically approve CSRs when a client bound to its role renews its own certificate.
These powers can be granted to credentials, such as bootstrapping tokens. For example, to replicate the behavior
provided by the removed auto-approval flag, of approving all CSRs by a single group:
```
# REMOVED: This flag no longer works as of 1.7.
--insecure-experimental-approve-all-kubelet-csrs-for-group="system:bootstrappers"
```
An admin would create a `ClusterRoleBinding` targeting that group.
For example, to grant these permissions to identities attached to bootstrap
tokens, an admin would create a `ClusterRoleBinding` targeting the
`system:bootstrappers` group:
```yml
# Approve all CSRs for the group "system:bootstrappers"
@@ -168,8 +179,8 @@ roleRef:
apiGroup: rbac.authorization.k8s.io
```
To let a node renew its own credentials, an admin can construct a `ClusterRoleBinding` targeting
that node's credentials:
To let all nodes renew their own credentials, an admin can create a
`ClusterRoleBinding` targeting node identities:
```yml
kind: ClusterRoleBinding
@@ -177,8 +188,8 @@ apiVersion: rbac.authorization.k8s.io/v1
metadata:
name: node1-client-cert-renewal
subjects:
- kind: User
name: system:node:node-1 # Let "node-1" renew its client certificate.
- kind: Group
name: system:nodes
apiGroup: rbac.authorization.k8s.io
roleRef:
kind: ClusterRole
@@ -186,18 +197,28 @@ roleRef:
apiGroup: rbac.authorization.k8s.io
```
Deleting the binding will prevent the node from renewing its client credentials, effectively
removing it from the cluster once its certificate expires.
## kubelet configuration
To request a client certificate from kube-apiserver, the kubelet first needs a path to a kubeconfig file that contains the
bootstrap authentication token. You can use `kubectl config set-cluster`, `set-credentials`, and `set-context` to build this kubeconfig. Provide the name `kubelet-bootstrap` to `kubectl config set-credentials` and include `--token=<token-value>` as follows:
To request a client certificate from kube-apiserver, the kubelet first needs a
path to a kubeconfig file that contains the credentials for the identity that it
will use to bootstrap its individual node identity.
If you are using a bootstrap token, you can use `kubectl config set-cluster`,
`set-credentials`, and `set-context` to build this kubeconfig. Provide the name
`kubelet-bootstrap` to `kubectl config set-credentials` and include
`--token=<token-value>` as follows:
```
kubectl config set-credentials kubelet-bootstrap --token=${BOOTSTRAP_TOKEN} --kubeconfig=bootstrap.kubeconfig
```
When starting the kubelet, if the file specified by `--kubeconfig` does not exist, the bootstrap kubeconfig is used to request a client certificate from the API server. On approval of the certificate request and receipt back by the kubelet, a kubeconfig file referencing the generated key and obtained certificate is written to the path specified by `--kubeconfig`. The certificate and key file will be placed in the directory specified by `--cert-dir`.
When starting the kubelet, if the file specified via `--kubeconfig` does not
exist, the bootstrap kubeconfig specified via `--bootstrap-kubeconfig` is used
to request a client certificate from the API server. On approval of the
certificate request and receipt back by the kubelet, a kubeconfig file
referencing the generated key and obtained certificate is written to the path
specified by `--kubeconfig`. The certificate and key file will be placed in the
directory specified by `--cert-dir`.
{{< note >}}
**Note:** The following flags are required to enable this bootstrapping when starting the kubelet:
@@ -207,25 +228,49 @@ When starting the kubelet, if the file specified by `--kubeconfig` does not exis
```
{{< /note >}}
Additionally, in 1.7 the kubelet implements __alpha__ features for enabling rotation of both its client and/or serving certs.
These can be enabled through the respective `RotateKubeletClientCertificate` and `RotateKubeletServerCertificate` feature
flags on the kubelet, but may change in backward incompatible ways in future releases.
Additionally, in 1.7 the kubelet implements __beta__ features for enabling
rotation of both its client and/or serving certs. These can be enabled through
the respective `RotateKubeletClientCertificate` and
`RotateKubeletServerCertificate` feature flags on the kubelet and are enabled by
default.
`RotateKubeletClientCertificate` causes the kubelet to rotate its client
certificates by creating new CSRs as its existing credentials expire. To enable
this feature pass the following flag to the kubelet:
```
--feature-gates=RotateKubeletClientCertificate=true,RotateKubeletServerCertificate=true
--rotate-certificates
```
`RotateKubeletClientCertificate` causes the kubelet to rotate its client certificates by creating new CSRs as its existing
credentials expire. `RotateKubeletServerCertificate` causes the kubelet to both request a serving certificate after
bootstrapping its client credentials and rotate the certificate. The serving cert currently does not request DNS or IP
SANs.
`RotateKubeletServerCertificate` causes the kubelet to both request a serving
certificate after bootstrapping its client credentials and to rotate that
certificate. To enable this feature pass the following flag to the kubelet:
```
--rotate-server-certificates
```
{{< note >}}
**Note:** The CSR approving controllers implemented in core Kubernetes do not
approve node serving certificates for [security
reasons](https://github.com/kubernetes/community/pull/1982). To use
`RotateKubeletServerCertificate` operators need to run a custom approving
controller, or manually approve the serving certificate requests.
{{< /note >}}
## kubectl approval
The signing controller does not immediately sign all certificate requests. Instead, it waits until they have been flagged with an
"Approved" status by an appropriately-privileged user. This is intended to eventually be an automated process handled by an external
approval controller, but for the alpha version of the API it can be done manually by a cluster administrator using kubectl.
An administrator can list CSRs with `kubectl get csr` and describe one in detail with `kubectl describe csr <name>`. Before the 1.6 release there were
[no direct approve/deny commands](https://github.com/kubernetes/kubernetes/issues/30163) so an approver had to update
the Status field directly ([rough how-to](https://github.com/gtank/csrctl)). Later versions of Kubernetes offer `kubectl certificate approve <name>` and `kubectl certificate deny <name>` commands.
CSRs can be approved outside of the approval flows builtin to the controller
manager.
The signing controller does not immediately sign all certificate requests.
Instead, it waits until they have been flagged with an "Approved" status by an
appropriately-privileged user. This flow is intended to allow for automated
approval handled by an external approval controller or the approval controller
implemented in the core controller-manager. However cluster administrators can
also manually approve certificate requests using kubectl. An administrator can
list CSRs with `kubectl get csr` and describe one in detail with `kubectl
describe csr <name>`. An administrator can approve or deny a CSR with `kubectl
certificate approve <name>` and `kubectl certificate deny <name>`.
{{% /capture %}}