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engine: remove deprecated orchestrator flag 

Signed-off-by: David Karlsson <35727626+dvdksn@users.noreply.github.com>
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David Karlsson 2023-11-10 09:14:39 +01:00
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content/engine/context/working-with-contexts.md
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@ -1,18 +1,24 @@
---
title: Docker Context
description: Learn about Docker Context
keywords: engine, context, cli, kubernetes
title: Docker contexts
description: Learn about managing multiple daemons from a single client with contexts
keywords: engine, context, cli, daemons, remote
---
## Introduction
This guide shows how _contexts_ make it easy for a **single Docker CLI** to manage multiple Swarm clusters, multiple Kubernetes clusters, and multiple individual Docker nodes.
This guide shows how you can use contexts to manage Docker daemons from a single client.
A single Docker CLI can have multiple contexts. Each context contains all of the endpoint and security information required to manage a different cluster or node. The `docker context` command makes it easy to configure these contexts and switch between them.
Each context contains all information required to manage resources on the daemon.
The `docker context` command makes it easy to configure these contexts and switch between them.
As an example, a single Docker client on your company laptop might be configured with two contexts; **dev-k8s** and **prod-swarm**. **dev-k8s** contains the endpoint data and security credentials to configure and manage a Kubernetes cluster in a development environment. **prod-swarm** contains everything required to manage a Swarm cluster in a production environment. Once these contexts are configured, you can use the top-level `docker context use <context-name>` to easily switch between them.
As an example, a single Docker client might be configured with two contexts:
For information on using Docker Context to deploy your apps to the cloud, see [Deploying Docker containers on Azure](../../cloud/aci-integration.md) and [Deploying Docker containers on ECS](../../cloud/ecs-integration.md).
- A default context running locally
- A remote, shared context
Once these contexts are configured,
you can use the `docker context use <context-name>` command
to switch between them.
## Prerequisites
@ -22,43 +28,39 @@ To follow the examples in this guide, you'll need:
Run `docker context` to verify that your Docker client supports contexts.
You will also need one of the following:
- Docker Swarm cluster
- Single-engine Docker node
- Kubernetes cluster
## The anatomy of a context
A context is a combination of several properties. These include:
- Name
- Name and description
- Endpoint configuration
- TLS info
- Orchestrator
The easiest way to see what a context looks like is to view the **default** context.
To list available contexts, use the `docker context ls` command.
```console
$ docker context ls
NAME DESCRIPTION DOCKER ENDPOINT KUBERNETES ENDPOINT ORCHESTRATOR
default * Current... unix:///var/run/docker.sock swarm
NAME DESCRIPTION DOCKER ENDPOINT ERROR
default * unix:///var/run/docker.sock
```
This shows a single context called "default". It's configured to talk to a Swarm cluster through the local `/var/run/docker.sock` Unix socket. It has no Kubernetes endpoint configured.
This shows a single context called "default".
It's configured to talk to a daemon through the local `/var/run/docker.sock` Unix socket.
The asterisk in the `NAME` column indicates that this is the active context. This means all `docker` commands will be executed against the "default" context unless overridden with environment variables such as `DOCKER_HOST` and `DOCKER_CONTEXT`, or on the command-line with the `--context` and `--host` flags.
The asterisk in the `NAME` column indicates that this is the active context.
This means all `docker` commands run against this context,
unless overridden with environment variables such as `DOCKER_HOST` and `DOCKER_CONTEXT`,
or on the command-line with the `--context` and `--host` flags.
Dig a bit deeper with `docker context inspect`. In this example, we're inspecting the context called `default`.
Dig a bit deeper with `docker context inspect`.
The following example shows how to inspect the context called `default`.
```console
$ docker context inspect default
[
{
"Name": "default",
"Metadata": {
"StackOrchestrator": "swarm"
},
"Metadata": {},
"Endpoints": {
"docker": {
"Host": "unix:///var/run/docker.sock",
@ -74,98 +76,83 @@ $ docker context inspect default
]
```
This context is using "swarm" as the orchestrator (`metadata.stackOrchestrator`). It is configured to talk to an endpoint exposed on a local Unix socket at `/var/run/docker.sock` (`Endpoints.docker.Host`), and requires TLS verification (`Endpoints.docker.SkipTLSVerify`).
### Create a new context
You can create new contexts with the `docker context create` command.
The following example creates a new context called "docker-test" and specifies the following:
- Default orchestrator = Swarm
- Issue commands to the local Unix socket `/var/run/docker.sock`
The following example creates a new context called `docker-test` and specifies
the host endpoint of the context to TCP socket `tcp://docker:2375`.
```console
$ docker context create docker-test \
--default-stack-orchestrator=swarm \
--docker host=unix:///var/run/docker.sock
$ docker context create docker-test --docker tcp://docker:2375
docker-test
Successfully created context "docker-test"
```
The new context is stored in a `meta.json` file below `~/.docker/contexts/`. Each new context you create gets its own `meta.json` stored in a dedicated sub-directory of `~/.docker/contexts/`.
> **Note:** The default context behaves differently than manually created contexts. It does not have a `meta.json` configuration file, and it dynamically updates based on the current configuration. For example, if you switch your current Kubernetes config using `kubectl config use-context`, the default Docker context will dynamically update itself to the new Kubernetes endpoint.
The new context is stored in a `meta.json` file below `~/.docker/contexts/`.
Each new context you create gets its own `meta.json` stored in a dedicated sub-directory of `~/.docker/contexts/`.
You can view the new context with `docker context ls` and `docker context inspect <context-name>`.
The following can be used to create a config with Kubernetes as the default orchestrator using the existing kubeconfig stored in `/home/ubuntu/.kube/config`. For this to work, you will need a valid kubeconfig file in `/home/ubuntu/.kube/config`. If your kubeconfig has more than one context, the current context (`kubectl config current-context`) will be used.
```console
$ docker context create k8s-test \
--default-stack-orchestrator=kubernetes \
--kubernetes config-file=/home/ubuntu/.kube/config \
--docker host=unix:///var/run/docker.sock
Successfully created context "k8s-test"
```
You can view all contexts on the system with `docker context ls`.
```console
$ docker context ls
NAME DESCRIPTION DOCKER ENDPOINT KUBERNETES ENDPOINT ORCHESTRATOR
default * Current unix:///var/run/docker.sock https://35.226.99.100 (default) swarm
k8s-test unix:///var/run/docker.sock https://35.226.99.100 (default) kubernetes
docker-test unix:///var/run/docker.sock swarm
NAME DESCRIPTION DOCKER ENDPOINT ERROR
default * unix:///var/run/docker.sock
docker-test tcp://docker:2375
```
The current context is indicated with an asterisk ("\*").
## Use a different context
You can use `docker context use` to quickly switch between contexts.
You can use `docker context use` to switch between contexts.
The following command will switch the `docker` CLI to use the "k8s-test" context.
The following command will switch the `docker` CLI to use the `docker-test` context.
```console
$ docker context use k8s-test
k8s-test
Current context is now "k8s-test"
$ docker context use docker-test
docker-test
Current context is now "docker-test"
```
Verify the operation by listing all contexts and ensuring the asterisk ("\*") is against the "k8s-test" context.
Verify the operation by listing all contexts and ensuring the asterisk ("\*") is against the `docker-test` context.
```console
$ docker context ls
NAME DESCRIPTION DOCKER ENDPOINT KUBERNETES ENDPOINT ORCHESTRATOR
default Current DOCKER_HOST based configuration unix:///var/run/docker.sock https://35.226.99.100 (default) swarm
docker-test unix:///var/run/docker.sock swarm
k8s-test * unix:///var/run/docker.sock https://35.226.99.100 (default) kubernetes
NAME DESCRIPTION DOCKER ENDPOINT ERROR
default unix:///var/run/docker.sock
docker-test * tcp://docker:2375
```
`docker` commands will now target endpoints defined in the "k8s-test" context.
`docker` commands will now target endpoints defined in the `docker-test` context.
You can also set the current context using the `DOCKER_CONTEXT` environment variable. This overrides the context set with `docker context use`.
You can also set the current context using the `DOCKER_CONTEXT` environment variable.
The environment variable overrides the context set with `docker context use`.
Use the appropriate command below to set the context to `docker-test` using an environment variable.
Windows PowerShell:
{{< tabs >}}
{{< tab name="PowerShell" >}}
```console
```ps
> $env:DOCKER_CONTEXT='docker-test'
```
Linux:
{{< /tab >}}
{{< tab name="Bash" >}}
```console
$ export DOCKER_CONTEXT=docker-test
```
Run a `docker context ls` to verify that the "docker-test" context is now the active context.
{{< /tab >}}
{{< /tabs >}}
You can also use the global `--context` flag to override the context specified by the `DOCKER_CONTEXT` environment variable. For example, the following will send the command to a context called "production".
Run `docker context ls` to verify that the `docker-test` context is now the
active context.
You can also use the global `--context` flag to override the context.
The following command uses a context called `production`.
```console
$ docker --context production container ls
@ -173,19 +160,16 @@ $ docker --context production container ls
## Exporting and importing Docker contexts
The `docker context` command makes it easy to export and import contexts on different machines with the Docker client installed.
You can use the `docker context export` and `docker context import` commands
to export and import contexts on different hosts.
You can use the `docker context export` command to export an existing context to a file. This file can later be imported on another machine that has the `docker` client installed.
The `docker context export` command exports an existing context to a file.
The file can be imported on any host that has the `docker` client installed.
By default, contexts will be exported as a _native Docker contexts_. You can export and import these using the `docker context` command. If the context you are exporting includes a Kubernetes endpoint, the Kubernetes part of the context will be included in the `export` and `import` operations.
### Exporting and importing a context
There is also an option to export just the Kubernetes part of a context. This will produce a native kubeconfig file that can be manually merged with an existing `~/.kube/config` file on another host that has `kubectl` installed. You cannot export just the Kubernetes portion of a context and then import it with `docker context import`. The only way to import the exported Kubernetes config is to manually merge it into an existing kubeconfig file.
Let's look at exporting and importing a native Docker context.
### Exporting and importing a native Docker context
The following example exports an existing context called "docker-test". It will be written to a file called `docker-test.dockercontext`.
The following example exports an existing context called `docker-test`.
It will be written to a file called `docker-test.dockercontext`.
```console
$ docker context export docker-test
@ -196,10 +180,10 @@ Check the contents of the export file.
```console
$ cat docker-test.dockercontext
meta.json0000644000000000000000000000022300000000000011023 0ustar0000000000000000{"Name":"docker-test","Metadata":{"StackOrchestrator":"swarm"},"Endpoints":{"docker":{"Host":"unix:///var/run/docker.sock","SkipTLSVerify":false}}}tls0000700000000000000000000000000000000000000007716 5ustar0000000000000000
```
This file can be imported on another host using `docker context import`. The target host must have the Docker client installed.
Import this file on another host using `docker context import`
to create context with the same configuration.
```console
$ docker context import docker-test docker-test.dockercontext
@ -211,61 +195,14 @@ You can verify that the context was imported with `docker context ls`.
The format of the import command is `docker context import <context-name> <context-file>`.
Now, let's look at exporting just the Kubernetes parts of a context.
### Exporting a Kubernetes context
You can export a Kubernetes context only if the context you are exporting has a Kubernetes endpoint configured. You cannot import a Kubernetes context using `docker context import`.
These steps will use the `--kubeconfig` flag to export **only** the Kubernetes elements of the existing `k8s-test` context to a file called "k8s-test.kubeconfig". The `cat` command will then show that it's exported as a valid kubeconfig file.
```console
$ docker context export k8s-test --kubeconfig
Written file "k8s-test.kubeconfig"
```
Verify that the exported file contains a valid kubectl config.
```console
$ cat k8s-test.kubeconfig
apiVersion: v1
clusters:
- cluster:
certificate-authority-data:
<Snip>
server: https://35.226.99.100
name: cluster
contexts:
- context:
cluster: cluster
namespace: default
user: authInfo
name: context
current-context: context
kind: Config
preferences: {}
users:
- name: authInfo
user:
auth-provider:
config:
cmd-args: config config-helper --format=json
cmd-path: /snap/google-cloud-sdk/77/bin/gcloud
expiry-key: '{.credential.token_expiry}'
token-key: '{.credential.access_token}'
name: gcp
```
You can merge this with an existing `~/.kube/config` file on another machine.
## Updating a context
You can use `docker context update` to update fields in an existing context.
The following example updates the "Description" field in the existing `k8s-test` context.
The following example updates the description field in the existing `docker-test` context.
```console
$ docker context update k8s-test --description "Test Kubernetes cluster"
k8s-test
Successfully updated context "k8s-test"
```
$ docker context update docker-test --description "Test context"
docker-test
Successfully updated context "docker-test"
```