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Release 1.8 (#5659)

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* GC now supports non-core resources

* Add two examples about how to analysis audits of kube-apiserver (#4264)

* Deprecate system:nodes binding

* [1.8] StatefulSet `initialized` annotation is now ignored.

* inits the kubeadm upgrade docs

addresses kubernetes/kubernetes.github.io/issues/4689

* adds kubeadm upgrade cmd to ToC

addresses kubernetes/kubernetes.github.io/issues/4689

* add workload placement docs

* ScaleIO - document udpate for 1.8

* Add documentation on storageClass.mountOptions and PV.mountOptions (#5254)

* Add documentation on storageClass.mountOptions and PV.mountOptions

* convert notes into callouts

* Add docs for CustomResource validation

add info about supported fields

* advanced audit beta features (#5300)

* Update job workload doc with backoff failure policy (#5319)

Add to the Jobs documentation how to use the new backoffLimit field that
limit the number of Pod failure before considering the Job as failed.

* Documented additional AWS Service annotations (#4864)

* Add device plugin doc under concepts/cluster-administration. (#5261)

* Add device plugin doc under concepts/cluster-administration.

* Update device-plugins.md

* Update device-plugins.md

Add meta description. Fix typo. Change bare metal deployment to manual deployment.

* Update device-plugins.md

Fix typo again.

* Update page.version. (#5341)

* Add documentation on storageClass.reclaimPolicy (#5171)

* [Advanced audit] use new herf for audit-api (#5349)

This tag contains all the changes in v1beta1 version. Update it now.

* Added documentation around creating the InitializerConfiguration for the persistent volume label controller in the cloud-controller-manager (#5255)

* Documentation for kubectl plugins (#5294)

* Documentation for kubectl plugins

* Update kubectl-plugins.md

* Update kubectl-plugins.md

* Updated CPU manager docs to match implementation. (#5332)

* Noted limitation of alpha static cpumanager.

* Updated CPU manager docs to match implementation.

- Removed references to CPU pressure node condition and evictions.
- Added note about new --cpu-manager-reconcile-period flag.
- Added note about node allocatable requirements for static policy.
- Noted limitation of alpha static cpumanager.

* Move cpu-manager task link to rsc mgmt section.

* init containers annotation removed in  1.8 (#5390)

* Add documentation for TaintNodesByCondition (#5352)

* Add documentation for TaintNodesByCondition

* Update nodes.md

* Update taint-and-toleration.md

* Update daemonset.md

* Update nodes.md

* Update taint-and-toleration.md

* Update daemonset.md

* Fix deployments (#5421)

* Document extended resources and OIR deprecation. (#5399)

* Document extended resources and OIR deprecation.

* Updated extended resources doc per reviews.

* reverts extra spacing in _data/tasks.yml

* addresses `kubeadm upgrade` review comments

Feedback from @chenopis, @luxas, and @steveperry-53 addressed with this commit

* HugePages documentation (#5419)

* Update cpu-management-policies.md (#5407)

Fixed the bad link.
Modified "cpu" to "CPU".
Added more 'yaml' as supplement.

* Update RBAC docs for v1 (#5445)

* Add user docs for pod priority and preemption (#5328)

* Add user docs for pod priority and preemption

* Update pod-priority-preemption.md

* More updates

* Update docs/admin/kubeadm.md for 1.8 (#5440)

- Made a couple of minor wording changes (not strictly 1.8 related).
 - Did some reformatting (not strictly 1.8 related).
 - Updated references to the default token TTL (was infinite, now 24 hours).
 - Documented the new `--discovery-token-ca-cert-hash` and `--discovery-token-unsafe-skip-ca-verification` flags for `kubeadm join`.
 - Added references to the new `--discovery-token-ca-cert-hash` flag in all the default examples.
 - Added a new _Security model_ section that describes the security tradeoffs of the various discovery modes.
 - Documented the new `--groups` flag for `kubeadm token create`.
 - Added a note of caution under _Automating kubeadm_ that references the _Security model_ section.
 - Updated the component version table to drop 1.6 and add 1.8.
 - Update `_data/reference.yml` to try to get the sidebar fixed up and more consistent with `kubefed`.

* Update StatefulSet Basics for 1.8 release (#5398)

* addresses `kubeadm upgrade` review comments

2nd iteration review comments by @luxas

* adds kubelet upgrade section to kubeadm upgrade

* Fix a bulleted list on docs/admin/kubeadm.md. (#5458)

I updated this doc yesterday and I was absolutely sure I fixed this, but I just saw that this commit got lost somehow.

This was introduced recently in https://github.com/kubernetes/kubernetes.github.io/pull/5440.

* Clarify the API to check for device plugins

* Moving Flexvolume to separate out-of-tree section

* addresses `kubeadm upgrade` review comments

CC: @luxas

* fixes kubeadm upgrade index

* Update Stackdriver Logging documentation (#5495)

* Re-update WordPress and MySQL PV doc to use apps/v1beta2 APIs (#5526)

* Update statefulset concepts doc to use apps/v1beta2 APIs (#5420)

* add document on kubectl's behavior regarding initializers (#5505)

* Update docs/admin/kubeadm.md to cover self-hosting in 1.8. (#5497)

This is a new beta feature in 1.8.

* Update kubectl patch doc to use apps/v1beta2 APIs (#5422)

* [1.8] Update "Run Applications" tasks to apps/v1beta2. (#5525)

* Update replicated stateful application task for 1.8.

* Update single instance stateful app task for 1.8.

* Update stateless app task for 1.8.

* Update kubectl patch task for 1.8.

* fix the link of persistent storage (#5515)

* update the admission-controllers.md index.md what-is-kubernetes.md link

* fix the link of persistent storage

* Add quota support for local ephemeral storage (#5493)

* Add quota support for local ephemeral storage

update the doc to this alpha feature

* Update resource-quotas.md

* Updated Deployments concepts doc (#5491)

* Updated Deployments concepts doc

* Addressed comments

* Addressed more comments

* Modify allocatable storage to ephemeral-storage (#5490)

Update the doc to use ephemeral-storage instead of storage

* Revamped concepts doc for ReplicaSet (#5463)

* Revamped concepts doc for ReplicaSet

* Minor changes to call out specific versions for selector defaulting and
immutability

* Addressed doc review comments

* Remove petset documentations (#5395)

* Update docs to use batch/v1beta1 cronjobs (#5475)

* add federation job doc (#5485)

* add federation job doc

* Update job.md

Edits for clarity and consistency

* Update job.md

Fixed a typo

* update DaemonSet concept for 1.8 release (#5397)

* update DaemonSet concept for 1.8 release

* Update daemonset.md

Fix typo. than -> then

* Update bootstrap tokens doc for 1.8. (#5479)

* Update bootstrap tokens doc for 1.8.

This has some changes I missed when I was updating the main kubeadm documention:
 - Bootstrap tokens are now beta, not alpha (https://github.com/kubernetes/features/issues/130)
 - The apiserver flag to enable the authenticator changedin 1.8 (https://github.com/kubernetes/kubernetes/pull/51198)
 - Added `auth-extra-groups` documentaion (https://github.com/kubernetes/kubernetes/pull/50933)
 - Updated the _Token Management with `kubeadm`_ section to link to the main kubeadm docs, since it was just duplicated information.

* Update bootstrap-tokens.md

* Updated the Cassandra tutorial to use apps/v1beta2 (#5548)

* add docs for AllowPrivilegeEscalation (#5448)

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

* Add local ephemeral storage alpha feature in managing compute resource (#5522)

* Add local ephemeral storage alpha feature in managing compute resource

Since 1.8, we add the local ephemeral storage alpha feature as one
resource type to manage. Add this feature into the doc.

* Update manage-compute-resources-container.md

* Update manage-compute-resources-container.md

* Update manage-compute-resources-container.md

* Update manage-compute-resources-container.md

* Update manage-compute-resources-container.md

* Update manage-compute-resources-container.md

* Added documentation for Metrics Server (#5560)

* authorization: improve authorization debugging docs (#5549)

* Document mount propagation (#5544)

* Update /docs/setup/independent/create-cluster-kubeadm.md for 1.8. (#5524)

This introduction needed a couple of small tweaks to cover the `--discovery-token-ca-cert-hash` flag added in https://github.com/kubernetes/kubernetes/pull/49520 and some version bumps.

* Add task doc for alpha dynamic kubelet configuration (#5523)

* Fix input/output of selfsubjectaccess review (#5593)

* Add docs for implementing resize (#5528)

* Add docs for implementing resize

* Update admission-controllers.md

* Added link to PVC section

* minor typo fixes

* Update NetworkPolicy concept guide with egress and CIDR changes (#5529)

* update zookeeper tutorial for 1.8 release

* add doc for hostpath type (#5503)

* Federated Hpa feature doc (#5487)

* Federated Hpa feature doc

* Federated Hpa feature doc review fixes

* Update hpa.md

* Update hpa.md

* update cloud controller manager docs for v1.8

* Update cronjob with defaults information (#5556)

* Kubernetes 1.8 reference docs (#5632)

* Kubernetes 1.8 reference docs

* Kubectl reference docs for 1.8

* Update side bar with 1.8 kubectl and api ref docs links

* remove petset.md

* update on state of HostAlias in 1.8 with hostNetwork Pod support (#5644)

* Fix cron job deletion section (#5655)

* update imported docs (#5656)

* Add documentation for certificate rotation. (#5639)

* Link to using kubeadm page

* fix the command output

fix the command output

* fix typo in api/resources reference: "Worloads"

* Add documentation for certificate rotation.

* Create TOC entry for cloud controller manager. (#5662)

* Updates for new versions of API types

* Followup 5655: fix link to garbage collection (#5666)

* Temporarily redirect resources-reference to api-reference. (#5668)

* Update config for 1.8 release. (#5661)

* Update config for 1.8 release.

* Address reviewer comments.

* Switch references in HPA docs from alpha to beta (#5671)

The HPA docs still referenced the alpha version.  This switches them to
talk about v2beta1, which is the appropriate version for Kubernetes 1.8

* Deprecate openstack heat (#5670)

* Fix typo in pod preset conflict example

Move container port definition to the correct line.

* Highlight openstack-heat provider deprecation

The openstack-heat provider for kube-up is being deprecated and will be
removed in a future release.

* Temporarily fix broken links by redirecting. (#5672)

* Fix broken links. (#5675)

* Fix render of code block (#5674)

* Fix broken links. (#5677)

* Add a small note about auto-bootstrapped CSR ClusterRoles (#5660)

* Update kubeadm install doc for v1.8 (#5676)

* add draft workloads api content for 1.8 (#5650)

* add draft workloads api content for 1.8

* edits per review, add tables, for 1.8 workloads api doc

* fix typo

* Minor fixes to kubeadm 1.8 upgrade guide. (#5678)

- The kubelet upgrade instructions should be done on every host, not
  just worker nodes.
- We should just upgrade all packages, instead of calling out kubelet
  specifically. This will also upgrade kubectl, kubeadm, and
  kubernetes-cni, if installed.
- Draining nodes should also ignore daemonsets, and master errors can be
  ignored.
- Make sure that the new kubeadm download is chmoded correctly.
- Add a step to run `kubeadm version` to verify after downloading.
- Manually approve new kubelet CSRs if rotation is enabled (known issue).

* Release 1.8 (#5680)

* Fix versions for 1.8 API ref docs

* Updates for 1.8 kubectl reference docs

* Kubeadm /docs/admin/kubeadm.md cleanup, editing. (#5681)

* Update docs/admin/kubeadm.md (mostly 1.8 related).

This is Fabrizio's work, which I'm committing along with my edits (in a commit on top of this).

* A few of my own edits to clarify and clean up some Markdown.
This commit is contained in:
Steve Perry
2017-09-28 21:46:51 -07:00
committed by GitHub
parent 88d3ed821d
commit 799eaf4229
1553 changed files with 318572 additions and 3286 deletions
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@@ -4,12 +4,17 @@ approvers:
- luxas
- errordeveloper
- jbeda
title: kubeadm Setup Tool Reference Guide
title: Kubeadm
notitle: true
---
# kubeadm Setup Tool Reference Guide
This document provides information on how to use kubeadm's advanced options.
Running `kubeadm init` bootstraps a Kubernetes cluster. This consists of the
* TOC
{:toc}
Running `kubeadm init` bootstraps a Kubernetes master node. This consists of the
following steps:
1. kubeadm runs a series of pre-flight checks to validate the system state
@@ -19,42 +24,72 @@ following steps:
1. kubeadm generates a token that additional nodes can use to register
themselves with the master in future. Optionally, the user can provide a
token.
token via `--token`, as described in the
[section on managing tokens](#manage-tokens) below.
1. kubeadm generates a self-signed CA to provision identities for each component
(including nodes) in the cluster. It also generates client certificates to
be used by various components. If the user has provided their own CA by
dropping it in the cert directory (configured via `--cert-dir`, by default
`/etc/kubernetes/pki`), this step is skipped.
dropping it in the cert directory configured via `--cert-dir`
(`/etc/kubernetes/pki` by default) this step is skipped as described in the
[section on using custom certificates](#custom-certificates).
1. Outputting a kubeconfig file for the kubelet to use to connect to the API
server, as well as an additional kubeconfig file for administration.
1. kubeadm writes kubeconfig files in `/etc/kubernetes/` for
the kubelet, the controller-manager and the scheduler to use to connect to the
API server, each one with their respective identities, as well as an additional
kubeconfig file for administration.
1. kubeadm generates Kubernetes static Pod manifests for the API server,
controller manager and scheduler. It places them in
`/etc/kubernetes/manifests`. The kubelet watches this directory for Pods to
create on startup. These are the core components of Kubernetes. Once they are
up and running kubeadm can set up and manage any additional components.
1. kubeadm generates static Pod manifests for the API server,
controller manager and scheduler; in case an external etcd is not provided,
an additional static Pod manifest will be generated for etcd.
1. kubeadm "taints" the master node so that only control plane components will
run there. It also sets up the RBAC authorization system and writes a
special ConfigMap that is used to bootstrap trust with the kubelets.
Static Pod manifests are written in `/etc/kubernetes/manifests`; the kubelet
watches this directory for Pods to create on startup, as described in
the [section about kubelet drop-in](#kubelet-drop-in).
Once control plane Pods are up and running kubeadm init sequence can continue.
1. kubeadm "labels" and "taints" the master node so that only control plane
components will run there.
1. Kubeadm makes all the necessary configurations for allowing node joining with the
[Bootstrap Tokens](https://kubernetes.io/docs/admin/bootstrap-tokens/) and
[TLS Bootstrap](https://kubernetes.io/docs/admin/kubelet-tls-bootstrapping/)
mechanism:
- Write a ConfigMap for making available all the information required
for joining and set up related RBAC access rules.
- Ensure access to the CSR signing API for bootstrap tokens.
- Configure auto approval for new CSR requests.
See [Securing your installation](#securing-more) for hardening.
1. kubeadm installs add-on components via the API server. Right now this is
the internal DNS server and the kube-proxy DaemonSet.
1. If `kubeadm init` is invoked with the alpha self-hosting feature enabled,
(`--feature-gates=SelfHosting=true`), the static Pod based control plane will
be transformed in a [self-hosed control plane](#self-hosting).
Running `kubeadm join` on each node in the cluster consists of the following
steps:
1. kubeadm downloads root CA information from the API server. It uses the token
to verify the authenticity of that data.
1. kubeadm downloads necessary cluster information from the API server.
By default, it uses the bootstrap token and the CA key hash to verify the
authenticity of that data. The root CA can also be discovered directly via a
file or URL.
1. kubeadm creates a local key pair. It prepares a certificate signing request
(CSR) and sends that off to the API server for signing. The bootstrap token
is used to authenticate. The control plane will sign this CSR requested
automatically.
1. Once the cluster information are known, kubelet can start the TLS bootstrapping
process (in v.1.7 this step was managed by kubeadm).
1. kubeadm configures the local kubelet to connect to the API server.
The TLS bootstrap uses the shared token to temporarily authenticate
with the Kubernetes Master to submit a certificate signing request (CSR); by
default the control plane will sign this CSR request automatically.
1. Finally, kubeadm will configures the local kubelet to connect to the API
server with the definitive identity assigned to the node.
## Usage
@@ -62,9 +97,8 @@ Fields that support multiple values do so either with comma separation, or by
specifying the flag multiple times.
The kubeadm command line interface is currently in **beta**. We are aiming to
not break any scripted use of the main `kubeadm init` and `kubeadm join`. The
single exception here is the format of the kubeadm config file as detailed
below. That format is still considered alpha and may change.
not break any scripted use of the main `kubeadm init` and `kubeadm join`.
Exceptions to this are documented below.
### `kubeadm init`
@@ -72,121 +106,140 @@ It is usually sufficient to run `kubeadm init` without any flags, but in some
cases you might like to override the default behaviour. Here we specify all the
flags that can be used to customise the Kubernetes installation.
**Options for `kubeadm init`:**
- `--apiserver-advertise-address`
This is the address the API Server will advertise to other members of the
cluster. This is also the address used to construct the suggested `kubeadm
join` line at the end of the init process. If not set (or set to 0.0.0.0) then
IP for the default interface will be used.
This is the address the API Server will advertise to other members of the
cluster. This is also the address used to construct the suggested `kubeadm
join` line at the end of the init process. If not set (or set to 0.0.0.0) then
IP for the default interface will be used.
This address is also added to the certificate that the API Server uses.
This address is also added to the certificate that the API Server uses.
- `--apiserver-bind-port`
The port that the API server will bind on. This defaults to 6443.
The port that the API server will bind on. This defaults to 6443.
- `--apiserver-cert-extra-sans`
Additional hostnames or IP addresses that should be added to the Subject
Alternate Name section for the certificate that the API Server will use. If you
expose the API Server through a load balancer and public DNS you could specify
this with
Additional hostnames or IP addresses that should be added to the Subject
Alternate Name section for the certificate that the API Server will use. If you
expose the API Server through a load balancer and public DNS you could specify
this with
```
--apiserver-cert-extra-sans=kubernetes.example.com,kube.example.com,10.100.245.1
```
```
--apiserver-cert-extra-sans=kubernetes.example.com,kube.example.com,10.100.245.1
```
- `--cert-dir`
The path where to save and store the certificates. The default is
"/etc/kubernetes/pki".
The path where to save and store the certificates. The default is
"/etc/kubernetes/pki".
- `--config`
A kubeadm specific [config file](#config-file). This can be used to specify an
extended set of options including passing arbitrary command line flags to the
control plane components.
A kubeadm specific [config file](#config-file). This can be used to specify an
extended set of options including passing arbitrary command line flags to the
control plane components.
**Note**: When providing configuration values using _both_ a configuration file
and flags, the file will take precedence. For example, if a file exists with:
**Note**: Since 1.8, other flags are not allowed alongside `--config` except
for flags used to define kubeadm behaviour (not configuration) such as
`--skip-preflight-checks`.
```yaml
apiVersion: kubeadm.k8s.io/v1alpha1
kind: MasterConfiguration
token: 1234
```
- `--dry-run`
and the user ran `kubeadm init --config file.yaml --token 5678`,
the chosen token value will be `1234`.
This flag tells kubeadm to don't apply any changes; just output what would be done.
- `--feature-gates`
A set of key=value pairs that describe feature gates for alpha/experimental
features. Options are:
- SelfHosting=true|false (ALPHA - default=false)
- StoreCertsInSecrets=true|false (ALPHA - default=false)
See [self-hosted control plane](#self-hosting) for more detail.
- `--kubernetes-version` (default 'latest') the kubernetes version to initialise
The **v1.6** version of kubeadm only supports building clusters that are at
least **v1.6.0**. There are many reasons for this including kubeadm's use of
RBAC, the Bootstrap Token system, and enhancements to the Certificates API. With
this flag you can try any future version of Kubernetes. Check [releases
page](https://github.com/kubernetes/kubernetes/releases) for a full list of
available versions.
The **v1.6** version of kubeadm only supports building clusters that are at
least **v1.6.0**. There are many reasons for this including kubeadm's use of
RBAC, the Bootstrap Token system, and enhancements to the Certificates API. With
this flag you can try any future version of Kubernetes. Check [releases
page](https://github.com/kubernetes/kubernetes/releases) for a full list of
available versions.
- `--node-name`
Allow to specify the node name, if something different than O.S. hostname should be used e.g. in case of Amazon EC2 instances.
The node-name is also added to the certificate that the API Server uses.
- `--pod-network-cidr`
For certain networking solutions the Kubernetes master can also play a role in
allocating network ranges (CIDRs) to each node. This includes many cloud
providers and flannel. You can specify a subnet range that will be broken down
and handed out to each node with the `--pod-network-cidr` flag. This should be a
minimum of a /16 so controller-manager is able to assign /24 subnets to each
node in the cluster. If you are using flannel with [this
manifest](https://github.com/coreos/flannel/blob/master/Documentation/kube-flannel.yml)
you should use `--pod-network-cidr=10.244.0.0/16`. Most CNI based networking
solutions do not require this flag.
For certain networking solutions the Kubernetes master can also play a role in
allocating network ranges (CIDRs) to each node. This includes many cloud
providers and flannel. You can specify a subnet range that will be broken down
and handed out to each node with the `--pod-network-cidr` flag. This should be a
minimum of a /16 so controller-manager is able to assign /24 subnets to each
node in the cluster. If you are using flannel with [this
manifest](https://github.com/coreos/flannel/blob/master/Documentation/kube-flannel.yml)
you should use `--pod-network-cidr=10.244.0.0/16`. Most CNI based networking
solutions do not require this flag.
- `--service-cidr` (default '10.96.0.0/12')
You can use the `--service-cidr` flag to override the subnet Kubernetes uses to
assign pods IP addresses. If you do, you will also need to update the
`/etc/systemd/system/kubelet.service.d/10-kubeadm.conf` file to reflect this
change else DNS will not function correctly.
You can use the `--service-cidr` flag to override the subnet Kubernetes uses to
assign pods IP addresses. If you do, you will also need to update the
`/etc/systemd/system/kubelet.service.d/10-kubeadm.conf` file to reflect this
change else DNS will not function correctly.
- `--service-dns-domain` (default 'cluster.local')
By default, `kubeadm init` deploys a cluster that assigns services with DNS
names `<service_name>.<namespace>.svc.cluster.local`. You can use the
`--service-dns-domain` to change the DNS name suffix. Again, you will need to
update the `/etc/systemd/system/kubelet.service.d/10-kubeadm.conf` file
accordingly else DNS will not function correctly.
By default, `kubeadm init` deploys a cluster that assigns services with DNS
names `<service_name>.<namespace>.svc.cluster.local`. You can use the
`--service-dns-domain` to change the DNS name suffix. Again, you will need to
update the `/etc/systemd/system/kubelet.service.d/10-kubeadm.conf` file
accordingly else DNS will not function correctly.
**Note**: This flag has an effect (it's needed for the kube-dns Deployment
manifest and the API Server's serving certificate) but not as you might expect,
since you will have to modify the arguments to the kubelets in the cluster for
it to work fully. Specifying DNS parameters using this flag only is not enough.
Rewriting the kubelet's CLI arguments is out of scope for kubeadm as it should
be agnostic to how you run the kubelet. However, making all kubelets in the
cluster pick up information dynamically via the API _is_ in scope and is a
[planned feature](https://github.com/kubernetes/kubeadm/issues/28) for upcoming
releases.
**Note**: This flag has an effect (it's needed for the kube-dns Deployment
manifest and the API Server's serving certificate) but not as you might expect,
since you will have to modify the arguments to the kubelets in the cluster for
it to work fully. Specifying DNS parameters using this flag only is not enough.
Rewriting the kubelet's CLI arguments is out of scope for kubeadm as it should
be agnostic to how you run the kubelet. However, making all kubelets in the
cluster pick up information dynamically via the API _is_ in scope and is a
[planned feature](https://github.com/kubernetes/kubeadm/issues/28) for upcoming
releases.
- `--skip-preflight-checks`
By default, kubeadm runs a series of preflight checks to validate the system
before making any changes. Advanced users can use this flag to bypass these if
necessary.
By default, kubeadm runs a series of preflight checks to validate the system
before making any changes. Advanced users can use this flag to bypass these if
necessary.
- `--skip-token-print`
By default, kubeadm prints the token at the end of the init procedure. Advanced
users can use this flag to bypass these if necessary.
- `--token`
By default, `kubeadm init` automatically generates the token used to initialise
each new node. If you would like to manually specify this token, you can use the
`--token` flag. The token must be of the format `[a-z0-9]{6}\.[a-z0-9]{16}`. A
compatible random token can be generated `kubeadm token generate`. Tokens can
be managed through the API after the cluster is created. See the [section on
managing tokens](#manage-tokens) below.
By default, `kubeadm init` automatically generates the token used to initialise
each new node. If you would like to manually specify this token, you can use the
`--token` flag. The token must be of the format `[a-z0-9]{6}\.[a-z0-9]{16}`. A
compatible random token can be generated `kubeadm token generate`. Tokens can
be managed through the API after the cluster is created. See the [section on
managing tokens](#manage-tokens) below.
- `--token-ttl`
This sets an expiration time for the token. This is specified as a duration
from the current time. After this time the token will no longer be valid and
will be removed. A value of 0 specifies that the token never expires. 0 is the
default. See the [section on managing tokens](#manage-tokens) below.
This sets an expiration time for the token. This is specified as a duration
from the current time. After this time the token will no longer be valid and
will be removed. A value of 0 specifies that the token never expires. The
default is 24 hours. See the [section on managing tokens](#manage-tokens) below.
### `kubeadm join`
@@ -194,15 +247,24 @@ When joining a kubeadm initialized cluster, we need to establish bidirectional
trust. This is split into discovery (having the Node trust the Kubernetes
master) and TLS bootstrap (having the Kubernetes master trust the Node).
There are 2 main schemes for discovery. The first is to use a shared token along
with the IP address of the API server. The second is to provide a file (a subset
of the standard kubeconfig file). This file can be a local file or downloaded
via an HTTPS URL. The forms are `kubeadm join --discovery-token
abcdef.1234567890abcdef 1.2.3.4:6443`, `kubeadm join --discovery-file
path/to/file.conf` or `kubeadm join --discovery-file https://url/file.conf`.
There are two main schemes for discovery:
- **Using a shared token** along with the IP address of the API server and a
hash of the root CA key:
`kubeadm join --discovery-token abcdef.1234567890abcdef --discovery-token-ca-cert-hash sha256:1234..cdef 1.2.3.4:6443`
- **Using a file** (a subset of the standard kubeconfig file). This file can
be a local file or downloaded via an HTTPS URL:
`kubeadm join --discovery-file path/to/file.conf`
`kubeadm join --discovery-file https://url/file.conf`
Only one form can be used. If the discovery information is loaded from a URL,
HTTPS must be used and the host installed CA bundle is used to verify the
connection.
connection. For details on the security tradeoffs of these mechanisms, see the
[security model](#security-model) section below.
The TLS bootstrap mechanism is also driven via a shared token. This is used to
temporarily authenticate with the Kubernetes master to submit a certificate
@@ -216,60 +278,124 @@ can be used instead of specifying the each token individually.
Here's an example on how to use it:
`kubeadm join --token=abcdef.1234567890abcdef 192.168.1.1:6443`
`kubeadm join --token=abcdef.1234567890abcdef --discovery-token-ca-cert-hash sha256:1234..cdef 192.168.1.1:6443`
Specific options:
**Options for `kubeadm join`:**
- `--config`
Extended options a specified in the [kubeadm specific config file](#config-file).
- `--skip-preflight-checks`
By default, kubeadm runs a series of preflight checks to validate the system
before making any changes. Advanced users can use this flag to bypass these if
necessary.
Extended options are specified in the [kubeadm specific config file](#config-file).
- `--discovery-file`
A local file path or HTTPS URL. The file specified must be a kubeconfig file
with nothing but an unnamed cluster entry. This is used to find both the
location of the API server to join along with a root CA bundle to use when
talking to that server.
A local file path or HTTPS URL. The file specified must be a kubeconfig file
with nothing but an unnamed cluster entry. This is used to find both the
location of the API server to join along with a root CA bundle to use when
talking to that server.
This might look something like this:
This might look something like this:
``` yaml
apiVersion: v1
clusters:
- cluster:
certificate-authority-data: <really long certificate data>
server: https://10.138.0.2:6443
name: ""
contexts: []
current-context: ""
kind: Config
preferences: {}
users: []
```
``` yaml
apiVersion: v1
clusters:
- cluster:
certificate-authority-data: <really long certificate data>
server: https://10.138.0.2:6443
name: ""
contexts: []
current-context: ""
kind: Config
preferences: {}
users: []
```
- `--discovery-token`
The discovery token is used along with the address of the API server (as an
unnamed argument) to download and verify information about the cluster. The
most critical part of the cluster information is the root CA bundle used to
verify the identity of the server during subsequent TLS connections.
The discovery token is used along with the address of the API server (as an
unnamed argument) to download and verify information about the cluster. The
most critical part of the cluster information is the root CA bundle used to
verify the identity of the server during subsequent TLS connections.
- `--discovery-token-ca-cert-hash`
The CA key hash is used to verify the full root CA certificate discovered during
token-based bootstrapping. It has the format `sha256:<hex_encoded_hash>`. By
default, the hash value is returned in the `kubeadm join` command printed at the
end of `kubeadm init`. It is in a standard format (see
[RFC7469](https://tools.ietf.org/html/rfc7469#section-2.4)) and can also be
calculated by 3rd party tools or provisioning systems. For example, using the
OpenSSL CLI:
`openssl x509 -pubkey -in /etc/kubernetes/pki/ca.crt | openssl rsa -pubin -outform der 2>&/dev/null | openssl dgst -sha256 -hex`
_Skipping this flag is allowed in Kubernetes 1.8, but makes certain spoofing
attacks possible._ See the [security model](#security-model) for details.
Pass `--discovery-token-unsafe-skip-ca-verification` to silence warnings (which
will become errors in Kubernetes 1.9).
- `--discovery-token-unsafe-skip-ca-verification`
Disable the warning/error that occurs when `--discovery-token-ca-cert-hash` is
not provided. Passing this flag is an acknowledgement of the
[security tradeoffs](#security-model) involved in skipping this verification
(which may or may not be appropriate in your environment).
- `--node-name`
Specify the Node name. The default is to use the OS hostname. This is useful
on some cloud providers such as AWS. This name is also added to the node's
TLS certificate.
- `--tls-bootstrap-token`
The token used to authenticate to the API server for the purposes of TLS
bootstrapping.
The token used to authenticate to the API server for the purposes of TLS
bootstrapping.
- `--token=<token>`
Often times the same token is used for both `--discovery-token` and
`--tls-bootstrap-token`. This option specifies the same token for both. Other
flags override this flag if present.
Often times the same token is used for both `--discovery-token` and
`--tls-bootstrap-token`. This option specifies the same token for both. Other
flags override this flag if present.
- `--skip-preflight-checks`
By default, kubeadm runs a series of preflight checks to validate the system
before making any changes. Advanced users can use this flag to bypass these if
necessary.
### `kubeadm completion`
Output shell completion code for the specified shell (bash or zsh).
### `kubeadm config`
Kubeadm v1.8.0+ automatically creates a ConfigMap with all the parameters
used during `kubeadm init`.
If you initialized your cluster using kubeadm v1.7.x or lower, you must use
the `kubeadm config upload` command to create this ConfigMap in order
for `kubeadm upgrade` to be able to configure your upgraded cluster correctly.
### `kubeadm reset`
Reverts any changes made to this host by `kubeadm init` or `kubeadm join`.
### `kubeadm token`
Manage tokens on a running cluster. See [managing tokens](#manage-tokens) below
for further details.
### `kubeadm alpha phases`
**WARNING:** While kubeadm command line interface is in beta, commands under
this entry is still considered alpha and may change in future versions.
`kubeadm phase` introduces a set of kubeadm CLI commands allowing to invoke
individually each phase of the kubeadm init sequence; phases provide a reusable
and composable API/toolbox for building your own automated cluster installer.
**Options for `kubeadm phases`:**
Each kubeadm phase exposes a subset of relevant options from `kubeadm init`.
## Using kubeadm with a configuration file {#config-file}
@@ -296,12 +422,18 @@ etcd:
caFile: <path|string>
certFile: <path|string>
keyFile: <path|string>
dataDir: <path|string>
extraArgs:
<argument>: <value|string>
<argument>: <value|string>
image: <string>
networking:
dnsDomain: <string>
serviceSubnet: <cidr>
podSubnet: <cidr>
kubernetesVersion: <string>
cloudProvider: <string>
nodeName: <string>
authorizationModes:
- <authorizationMode1|string>
- <authorizationMode2|string>
@@ -321,6 +453,11 @@ apiServerCertSANs:
- <name1|string>
- <name2|string>
certificatesDir: <string>
imageRepository: <string>
unifiedControlPlaneImage: <string>
featureGates:
<feature>: <bool>
<feature>: <bool>
```
In addition, if authorizationMode is set to `ABAC`, you should write the config to `/etc/kubernetes/abac_policy.json`.
However, if authorizationMode is set to `Webhook`, you should write the config to `/etc/kubernetes/webhook_authz.conf`.
@@ -336,10 +473,16 @@ discoveryToken: <string>
discoveryTokenAPIServers:
- <address|string>
- <address|string>
nodeName: <string>
tlsBootstrapToken: <string>
token: <string>
discoveryTokenCACertHashes:
- <SHA-256 hash|string>
- <SHA-256 hash|string>
discoveryTokenUnsafeSkipCAVerification: <bool>
```
## Securing your installation even more
## Securing your installation even more {#securing-more}
The defaults for kubeadm may not work for everyone. This section documents how to tighten up a kubeadm install
at the cost of some usability.
@@ -414,34 +557,53 @@ created cluster (`/etc/kubernetes/admin.conf`). You can specify an alternate
kubeconfig file for credentials with the `--kubeconfig` to the following
commands.
* `kubeadm token list` Lists the tokens along with when they expire and what the
approved usages are.
* `kubeadm token create` Creates a new token.
* `--description` Set the description on the new token.
* `--ttl duration` Set expiration time of the token as a delta from "now".
Default is 0 for no expiration. The unit of the duration is seconds.
* `--usages` Set the ways that the token can be used. The default is
`signing,authentication`. These are the usages as described above.
* `kubeadm token delete <token id>|<token id>.<token secret>` Delete a token.
The token can either be identified with just an ID or with the entire token
value. Only the ID is used; the token is still deleted if the secret does not
match.
* `kubeadm token list` - List tokens (along with their expirations, usages, and groups).
In addition, you can use the `kubeadm token generate` command to locally creates
a new token. This token is of the correct form for specifying with the
`--token` argument to `kubeadm init`.
* `kubeadm token create` - Create a new token.
* `--description <description>`
Set the human-readable description for the new token.
* `--ttl <duration>`
Set the expiration time-to-live of the token relative to the current time.
Default is 24 hours. A value of 0 means "never expire". The default unit
of the duration is seconds but other units can be specified (e.g., `15m`, `1h`).
* `--usages <usage>[,<usage>...]`
Set the ways that the token can be used. The default is
`signing,authentication`. These are the usages as described above.
* `--groups <group>[,<group>...]`
Add extra bootstrap groups that the new token will authenticate as. Can be
specified multiple times. Each extra group must start with
`system:bootstrappers:`. This is an advanced feature meant for custom
bootstrap scenarios where you want to change how CSR approval works for
different groups of nodes.
* `kubeadm token delete <token id>|<token id>.<token secret>` - Delete a token.
The token can either be identified with just an ID or with the
entire token value. Only the ID is used; the token is still deleted if the
secret does not match.
* `kubeadm token generate` - Generate a token locally.
Locally generate a token but do not create it on the server. This token is of
the correct form for specifying with the `--token` argument to `kubeadm init`.
For the gory details on how the tokens are implemented (including managing them
outside of kubeadm) see the [Bootstrap Token
docs](/docs/admin/bootstrap-tokens/).
outside of kubeadm) see the [Bootstrap Token docs](/docs/admin/bootstrap-tokens/).
## Automating kubeadm
Rather than copying the token you obtained from `kubeadm init` to each node, as
in the [basic kubeadm tutorial](/docs/admin/kubeadm/), you can
parallelize the token distribution for easier automation. To implement this
automation, you must know the IP address that the master will have after it is
started.
in the [basic kubeadm tutorial](/docs/admin/kubeadm/), you can parallelize the
token distribution for easier automation. To implement this automation, you must
know the IP address that the master will have after it is started.
1. Generate a token. This token must have the form `<6 character string>.<16
character string>`. More formally, it must match the regex:
@@ -460,21 +622,115 @@ started.
Once the cluster is up, you can grab the admin credentials from the master node
at `/etc/kubernetes/admin.conf` and use that to talk to the cluster.
## Use Kubeadm with other CRI runtimes
Note that this style of bootstrap has some relaxed security guarantees because
it does not allow the root CA hash to be validated with
`--discovery-token-ca-cert-hash` (since it's not generated when the nodes are
provisioned). For details, see the [security model](#security-model).
Since [Kubernetes 1.6 release](https://github.com/kubernetes/kubernetes/blob/master/CHANGELOG.md#node-components-1), Kubernetes container runtimes have been transferred to using CRI by default. Currently, the build-in container runtime is Docker which is enabled by build-in `dockershim` in `kubelet`.
## Security model
The kubeadm discovery system has several options, each with security tradeoffs.
The right method for your environment depends on how you provision nodes and the
security expectations you have about your network and node lifecycles.
Using other CRI based runtimes with kubeadm is very simple, and currently supported runtimes are:
### Token-based discovery with CA pinning
_This is the default mode in Kubernetes 1.8._ In this mode, kubeadm downloads
the cluster configuration (including root CA) and validates it using the token
as well as validating that the root CA public key matches the provided hash and
that the API server certificate is valid under the root CA.
**Example `kubeadm join` command:**
- `kubeadm join --discovery-token abcdef.1234567890abcdef --discovery-token-ca-cert-hash sha256:1234..cdef 1.2.3.4:6443`
**Advantages:**
- Allows bootstrapping nodes to securely discover a root of trust for the
master even if other worker nodes or the network are compromised.
- Convenient to execute manually since all of the information required fits
into a single `kubeadm join` command that is easy to copy and paste.
**Disadvantages:**
- The CA hash is not normally known until the master has been provisioned,
which can make it more difficult to build automated provisioning tools that
use kubeadm.
### Token-based discovery without CA pinning
_This was the default in Kubernetes 1.7 and earlier_, but comes with some
important caveats. This mode relies only on the symmetric token to sign
(HMAC-SHA256) the discovery information that establishes the root of trust for
the master. It's still possible in Kubernetes 1.8 and above using the
`--discovery-token-unsafe-skip-ca-verification` flag, but you should consider
using one of the other modes if possible.
**Example `kubeadm join` command:**
- `kubeadm join --discovery-token abcdef.1234567890abcdef --discovery-token-unsafe-skip-ca-verification 1.2.3.4:6443`
**Advantages:**
- Still protects against many network-level attacks.
- The token can be generated ahead of time and shared with the master and
worker nodes, which can then bootstrap in parallel without coordination. This
allows it to be used in many provisioning scenarios.
**Disadvantages:**
- If an attacker is able to steal a bootstrap token via some vulnerability,
they can use that token (along with network-level access) to impersonate the
master to other bootstrapping nodes. This may or may not be an appropriate
tradeoff in your environment.
### File or HTTPS-based discovery
This provides an out-of-band way to establish a root of trust between the master
and bootstrapping nodes. Consider using this mode if you are building automated provisioning
using kubeadm.
**Example `kubeadm join` commands:**
- `kubeadm join --discovery-file path/to/file.conf` (local file)
- `kubeadm join --discovery-file https://url/file.conf` (remote HTTPS URL)
**Advantages:**
- Allows bootstrapping nodes to securely discover a root of trust for the
master even if other worker nodes or the network are compromised.
**Disadvantages:**
- Requires that you have some way to carry the discovery information from
the master to the bootstrapping nodes. This might be possible, for example,
via your cloud provider or provisioning tool. The information in this file is
not secret, but HTTPS or equivalent is required to ensure its integrity.
- Less convenient to use manually since the file is difficult to copy and paste
between nodes.
## Use kubeadm with other CRI runtimes
Since [Kubernetes 1.6 release](https://github.com/kubernetes/kubernetes/blob/master/CHANGELOG.md#node-components-1),
Kubernetes container runtimes have been transferred to using CRI by default.
Currently, the build-in container runtime is Docker which is enabled by built-in
`dockershim` in `kubelet`.
Using other CRI based runtimes with kubeadm is very simple, and currently
supported runtimes are:
- [cri-o](https://github.com/kubernetes-incubator/cri-o)
- [frakti](https://github.com/kubernetes/frakti)
- [rkt](https://github.com/kubernetes-incubator/rktlet)
After you have successfully installed `kubeadm` and `kubelet`, please follow these two steps:
After you have successfully installed `kubeadm` and `kubelet`, please follow
these two steps:
1. Install runtime shim on every node. You will need to follow the installation document in the runtime shim project listing above.
1. Install runtime shim on every node. You will need to follow the installation
document in the runtime shim project listing above.
2. Configure kubelet to use remote CRI runtime. Please remember to change `RUNTIME_ENDPOINT` to your own value like `/var/run/{your_runtime}.sock`:
1. Configure kubelet to use remote CRI runtime. Please remember to change
`RUNTIME_ENDPOINT` to your own value like `/var/run/{your_runtime}.sock`:
```shell
$ cat > /etc/systemd/system/kubelet.service.d/20-cri.conf <<EOF
@@ -483,7 +739,22 @@ EOF
$ systemctl daemon-reload
```
Now `kubelet` is ready to use the specified CRI runtime, and you can continue with `kubeadm init` and `kubeadm join` workflow to deploy Kubernetes cluster.
Now `kubelet` is ready to use the specified CRI runtime, and you can continue
with `kubeadm init` and `kubeadm join` workflow to deploy Kubernetes cluster.
## Using custom images {#custom-images}
By default, kubeadm will pull images from `gcr.io/google_containers`, unless
requested kubernetes version is a ci version; in this case
`gcr.io/kubernetes-ci-image` will be used.
This behaviour can be overridden by [using kubeadm with a configuration file](#config-file).
Allowed customization are:
- provide an alternative `imageRepository` to be used instead of
`gcr.io/google_containers` (NB. does not works for ci version)
- provide an `unifiedControlPlaneImage` to be used instead of single images
for control plane components
- provide an `etcd.image` name to be used
## Running kubeadm without an internet connection
@@ -492,23 +763,23 @@ the following images are required for the cluster works will be automatically
pulled by the kubelet if they don't exist locally while `kubeadm init` is initializing
your master:
| Image Name | v1.6 release branch version | v1.7 release branch version
| Image Name | v1.7 release branch version | v1.8 release branch version
|---|---|---|
| gcr.io/google_containers/kube-apiserver-${ARCH} | v1.6.x | v1.7.x
| gcr.io/google_containers/kube-controller-manager-${ARCH} | v1.6.x | v1.7.x
| gcr.io/google_containers/kube-scheduler-${ARCH} | v1.6.x | v1.7.x
| gcr.io/google_containers/kube-proxy-${ARCH} | v1.6.x | v1.7.x
| gcr.io/google_containers/kube-apiserver-${ARCH} | v1.7.x | v1.8.x
| gcr.io/google_containers/kube-controller-manager-${ARCH} | v1.7.x | v1.8.x
| gcr.io/google_containers/kube-scheduler-${ARCH} | v1.7.x | v1.8.x
| gcr.io/google_containers/kube-proxy-${ARCH} | v1.7.x | v1.8.x
| gcr.io/google_containers/etcd-${ARCH} | 3.0.17 | 3.0.17
| gcr.io/google_containers/pause-${ARCH} | 3.0 | 3.0
| gcr.io/google_containers/k8s-dns-sidecar-${ARCH} | 1.14.1 | 1.14.4
| gcr.io/google_containers/k8s-dns-kube-dns-${ARCH} | 1.14.1 | 1.14.4
| gcr.io/google_containers/k8s-dns-dnsmasq-nanny-${ARCH} | 1.14.1 | 1.14.4
| gcr.io/google_containers/k8s-dns-sidecar-${ARCH} | 1.14.4 | 1.14.4
| gcr.io/google_containers/k8s-dns-kube-dns-${ARCH} | 1.14.4 | 1.14.4
| gcr.io/google_containers/k8s-dns-dnsmasq-nanny-${ARCH} | 1.14.4 | 1.14.4
Here `v1.7.x` means the "latest patch release of the v1.7 branch".
`${ARCH}` can be one of: `amd64`, `arm`, `arm64`, `ppc64le` or `s390x`.
## Managing the kubeadm drop-in file for the kubelet
## Managing the kubeadm drop-in file for the kubelet {#kubelet-drop-in}
The kubeadm deb package ships with configuration for how the kubelet should
be run. Note that the `kubeadm` CLI command will never touch this drop-in file.
@@ -534,7 +805,7 @@ A breakdown of what/why:
tells the kubelet where the API server is. This file also has the kubelet's
credentials.
* `--require-kubeconfig=true` the kubelet should fail fast if the kubeconfig file
is not present. This makes the kubelet crashloop during the time the service is
is not present. This makes the kubelet crash loop during the time the service is
started until `kubeadm init` is run.
* `--pod-manifest-path=/etc/kubernetes/manifests` specifies from where to read
Static Pod manifests used for spinning up the control plane
@@ -562,7 +833,7 @@ A breakdown of what/why:
systemctl restart kubelet
```
## Cloudprovider integrations (experimental)
## Cloud provider integrations (experimental)
Enabling specific cloud providers is a common request. This currently requires
manual configuration and is therefore not yet fully supported. If you wish to do
@@ -573,7 +844,7 @@ installed on the host, for example for volume mounting/unmounting, install those
packages.
Specify the `--cloud-provider` flag for the kubelet and set it to the cloud of your
choice. If your cloudprovider requires a configuration file, create the file
choice. If your cloud provider requires a configuration file, create the file
`/etc/kubernetes/cloud-config` on every node. The exact format and content of
that file depends on the requirements imposed by your cloud provider. If you use
the `/etc/kubernetes/cloud-config` file, you must append it to the kubelet
@@ -604,19 +875,19 @@ help to fully automate this process in the future.
## Environment variables
**Note:** These environment variables are deprecated and will stop functioning in v1.8!
There are some environment variables that modify the way that kubeadm works.
Most users will have no need to set these. These environment variables are a
short-term solution, eventually they will be integrated in the kubeadm
configuration file.
**Note:** These environment variables are deprecated and will stop functioning in v1.8!
| Variable | Default | Description |
| --- | --- | --- |
| `KUBE_KUBERNETES_DIR` | `/etc/kubernetes` | Where most configuration files are written to and read from |
| `KUBE_HYPERKUBE_IMAGE` | | If set, use a single hyperkube image with this name. If not set, individual images per server component will be used. |
| `KUBE_ETCD_IMAGE` | `gcr.io/google_containers/etcd-<arch>:3.0.17` | The etcd container image to use. |
| `KUBE_REPO_PREFIX` | `gcr.io/google_containers` | The image prefix for all images that are used. |
| Variable | Default | Description |
| ---------------------- | --------------------------------------------- | ---------------------------------------- |
| `KUBE_KUBERNETES_DIR` | `/etc/kubernetes` | Where most configuration files are written to and read from |
| `KUBE_HYPERKUBE_IMAGE` | | If set, use a single hyperkube image with this name. If not set, individual images per server component will be used. |
| `KUBE_ETCD_IMAGE` | `gcr.io/google_containers/etcd-<arch>:3.0.17` | The etcd container image to use. |
| `KUBE_REPO_PREFIX` | `gcr.io/google_containers` | The image prefix for all images that are used. |
If `KUBE_KUBERNETES_DIR` is specified, you may need to rewrite the arguments of the kubelet.
(e.g. --kubeconfig, --pod-manifest-path)
@@ -656,7 +927,7 @@ export no_proxy="localhost,127.0.0.1,localaddress,.localdomain.com,example.com,1
Remember to change `proxy_ip` and add a kube master node IP address to
`no_proxy`.
## Using custom certificates
## Using custom certificates {#custom-certificates}
By default kubeadm will generate all the certificates needed for a cluster to run.
You can override this behaviour by providing your own certificates.
@@ -673,6 +944,65 @@ This means you can, for example, prepopulate `/etc/kubernetes/pki/ca.crt`
and `/etc/kubernetes/pki/ca.key` with an existing CA, which then will be used
for signing the rest of the certs.
Only for the CA, it is possible to provide the `ca.crt` file but not the `ca.key`
file; if all other certificates and kubeconfig files already are in place kubeadm
recognise this condition and activates the so called "ExternalCA" mode, which also
implies the csrsignercontroller in controller-manager won't be started.
## Self-hosting the Kubernetes control plane {#self-hosting}
As of 1.8, kubeadm can experimentally create a _self-hosted_ Kubernetes control
plane. This means that key components such as the API server, controller
manager, and scheduler run as [DaemonSet pods](/docs/concepts/workloads/controllers/daemonset/)
configured via the Kubernetes API instead of [static pods](/docs/tasks/administer-cluster/static-pod/)
configured in the kubelet via static files.
Self-hosting is alpha in kubeadm 1.8 but is expected to become the default in
a future version. To create a self-hosted cluster, pass the `--feature-gates=SelfHosting=true`
flag to `kubeadm init`.
#### Caveats
Kubeadm self-hosting in 1.8 has some important limitations. In particular, a
self-hosted cluster cannot currently recover from a reboot of the master node
without manual intervention. This and other limitations are expected to be
resolved before self-hosting graduates from alpha.
By default, self-hosted control plane pods rely on credentials loaded from
[`hostPath`](https://kubernetes.io/docs/concepts/storage/volumes/#hostpath)
volumes. Except for initial creation, these credentials are not managed by
kubeadm. You can use `--feature-gates=StoreCertsInSecrets=true` to enable an
experimental mode where control plane credentials are loaded from Secrets
instead. This requires very careful control over the authentication and
authorization configuration for your cluster, and may not be appropriate for
your environment.
In 1.8, the self-hosted portion of the control plane does not include etcd,
which still runs as a static pod.
#### Process
The self-hosting bootstrap process is documented in [the kubeadm 1.8 design
document](https://github.com/kubernetes/kubeadm/blob/master/docs/design/design_v1.8.md#optional-self-hosting).
In summary, `kubeadm init --feature-gates=SelfHosting=true` works as follows:
1. As usual, kubeadm creates static pod YAML files in `/etc/kubernetes/manifests/`.
1. Kubelet loads these files and launches the initial static control plane.
Kubeadm waits for this initial static control plane to be running and
healthy. This is identical to the `kubeadm init` process without self-hosting.
1. Kubeadm uses the static control plane pod manifests to construct a set of
DaemonSet manifests that will run the self-hosted control plane.
1. Kubeadm creates DaemonSets in the `kube-system` namespace and waits for the
resulting pods to be running.
1. Once the new control plane is running (but not yet active), kubeadm deletes
the static pod YAML files. This triggers kubelet to stop those static pods.
1. When the original static control plane stops, the new self-hosted control
plane is able to bind to listening ports and become active.
This process (steps 3-6) can also be triggered with `kubeadm phase selfhosting convert-from-staticpods`.
## Releases and release notes
If you already have kubeadm installed and want to upgrade, run `apt-get update