Skip to content

Commit bb0d273

Browse files
lmktfylmktfy
committed
Add overview page for Configuration
1 parent 238ee64 commit bb0d273

File tree

1 file changed

+129
-1
lines changed
  • content/en/docs/concepts/configuration

1 file changed

+129
-1
lines changed

‎content/en/docs/concepts/configuration/_index.md‎

Lines changed: 129 additions & 1 deletion
Original file line numberDiff line numberDiff line change
@@ -2,6 +2,134 @@
22
title: "Configuration"
33
weight: 80
44
description: >
5-
Resources that Kubernetes provides for configuring Pods.
5+
Configuration mechanisms within Kubernetes.
6+
simple_list: true
67
---
78

9+
Kubernetes provides ways to _separate configuration from code_. This is a common
10+
practice that aligns with DevOps as a practice, and with cloud native architecture.
11+
12+
If you have a {{< glossary_tooltip text="container image" term_id="image" >}} that
13+
allows separate configuration, you can deploy the **same** application code in
14+
different contexts. For example, you can run tests against the built image, and
15+
then run that exact same image in a production context. Doing that gives you
16+
better confidence in your testing, compared with if you deployed the application
17+
one way for tests and a different way in production.
18+
19+
If you wanted to learn about configuring the `kubectl` command line tool,
20+
read [configure access to multiple clusters](/docs/tasks/access-application-cluster/configure-access-multiple-clusters/).
21+
22+
<!-- body -->
23+
## Kubernetes configuration-related APIs {#api-kinds}
24+
25+
Kubernetes provides two main API kinds that you can use to store configuration,
26+
ready for a Pod (or other component) to load and use:
27+
[ConfigMap](/docs/concepts/configuration/configmap/), and
28+
[Secret](/docs/concepts/configuration/secret/).
29+
30+
The special-use
31+
[CertificateSigningRequest](/docs/reference/access-authn-authz/certificate-signing-requests/#certificate-signing-requests)
32+
and
33+
[ClusterTrustBundle](/docs/reference/access-authn-authz/certificate-signing-requests/#cluster-trust-bundles)
34+
API kinds also hold configuration data that's relevant to some specific cases,
35+
such as TLS configuration.
36+
37+
All of these mechanisms can be shared across multiple Pods. You typically don't
38+
have to write the configuration out once per Pod, and you should design applications
39+
where possible so that they can work with shared configuration.
40+
41+
To learn about using configuration in your applications, read
42+
[inject data into applications](/docs/tasks/inject-data-application/).
43+
44+
### ConfigMaps
45+
46+
{{< glossary_definition term_id="configmap" prepend="A ConfigMap is" length="all" >}}
47+
48+
### Secrets
49+
50+
A Secret is an object that contains an amount of confidential data,
51+
such as a password, a token, or a key.
52+
53+
Secrets are similar to {{< glossary_tooltip text="ConfigMaps" term_id="configmap" >}}
54+
but are specifically intended to hold confidential data. Read the page about Secrets
55+
to learn about the benefits (and limitations) around information security and Secrets.
56+
57+
## Configuration via helper containers {#config-helper-overview}
58+
59+
You can also use an
60+
{{< glossary_tooltip text="init container" term_id="init-container" >}} or a
61+
{{< glossary_tooltip text="sidecar container" term_id="sidecar-container" >}}
62+
to provide configuration to your workload.
63+
64+
This is useful if you already have some means, outside of Kubernetes, to store
65+
configuration or security keys or other information that your containers must
66+
use, and that shouldn't be stored in container images.
67+
68+
### Sidecar container helper {#config-helper-sidecar}
69+
70+
A _sidecar_ configuration helper runs in the same Pod as the application container, so
71+
each Pod has its own sidecar. A typical configuration sidecar fetches configuration data over the
72+
Pod network, and then writes it into a {{< glossary_tooltip text="volume" term_id="volume" >}}
73+
that is mounted into both containers.
74+
75+
There are many variations on this basic pattern, that still have a helper
76+
container writing configuration for the app container to consume.
77+
78+
### Init container helper {#config-helper-init-container}
79+
80+
Pods can have _init_ containers that start before the main application. Unlike sidecars,
81+
init containers complete before the Pod's main (application) containers start up, so the
82+
configuration only gets set once.
83+
84+
You have two main options for configuration using init containers:
85+
86+
#### Configuration via the filesystem {#init-container-shared-volume}
87+
88+
With this option, the init container fetches configuration and writes the configuration to
89+
a file, or several files, typically to a Pod-local
90+
{{< glossary_tooltip text="volume" term_id="volume" >}}.
91+
92+
#### Configuration via environment variables {#init-container-env-files}
93+
94+
{{< feature-state feature_gate_name="EnvFiles" >}}
95+
96+
This is done using a local volume, but only the init container mounts that volume. The kubelet then reads from that volume before starting the app container.
97+
98+
Read [Define Environment Variable Values Using An Init Container](/docs/tasks/inject-data-application/define-environment-variable-via-file/)
99+
to learn more.
100+
101+
## Cluster configuration
102+
103+
Depending on the role you have, you may also need to configure your cluster.
104+
To learn more about that, read
105+
[cluster administration](/docs/concepts/cluster-administration/) and
106+
look through the list of [cluster administration tasks](/docs/tasks/administer-cluster/).
107+
108+
## {{% heading "whatsnext" %}}
109+
110+
The following links are all relevant to the overall idea of _configuration_ and Kubernetes:
111+
112+
* [Management of Kubernetes Objects Using Configuration Files](/docs/tasks/manage-kubernetes-objects/declarative-config/),
113+
which is about Kubernetes {{< glossary_tooltip text="manifests" term_id="manifest" >}}
114+
* [Kubernetes Object Management](/docs/concepts/overview/working-with-objects/object-management/) is also about object management / configuration
115+
* [Configure Redis Using A ConfigMap](/docs/tutorials/configuration/configure-redis-using-configmap/).
116+
a tutorial
117+
* [Updating Configuration via a ConfigMap](/docs/tutorials/configuration/updating-configuration-via-a-configmap/)
118+
(another tutorial)
119+
* [Inject Data Into Applications](/docs/tasks/inject-data-application/)
120+
* [Configure Pods and Containers](/docs/tasks/configure-pod-container/)
121+
* [Cluster Administration](/docs/concepts/cluster-administration/)
122+
* [API server authentication configuration](/docs/reference/access-authn-authz/authentication/#using-authentication-configuration)
123+
* [API server authorization configuration](/docs/reference/access-authn-authz/authorization/#using-configuration-file-for-authorization)
124+
* [Configure Certificate Rotation for the Kubelet](/docs/tasks/tls/certificate-rotation/)
125+
* [Reconfiguring a `kubeadm` Cluster](/docs/tasks/administer-cluster/kubeadm/kubeadm-reconfigure/)
126+
* [Configuring a CGroup Driver](/docs/tasks/administer-cluster/kubeadm/configure-cgroup-driver/)
127+
* [Create Static Pods](/docs/tasks/configure-pod-container/static-pod/), relevant to
128+
control plane configuration
129+
* [Configure the Aggregation Layer](/docs/tasks/extend-kubernetes/configure-aggregation-layer/)
130+
* [Policies](/docs/concepts/policy/), another form of configuration
131+
132+
and you can review the [list of configuration file formats](/docs/reference/config-api/)
133+
in the reference section.
134+
135+
Within **this** section of the documentation, you can read about:

0 commit comments

Comments
 (0)