Combine topic on commands and args. (#3637)
* Combine topic on commands and args. * Fix redirect.reviewable/pr3638/r1
Steve Perry
GitHub
parent
1cc0b4b93a
commit
fc533bea91
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@ -86,7 +86,6 @@ toc:
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- title: Configuration
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section:
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- docs/concepts/configuration/overview.md
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- docs/concepts/configuration/container-command-args.md
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- docs/concepts/configuration/manage-compute-resources-container.md
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- docs/concepts/configuration/assign-pod-node.md
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- docs/concepts/configuration/secret.md
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@ -1,88 +0,0 @@
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---
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title: Container Command and Arguments
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redirect_from:
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- "/docs/user-guide/containers/"
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- "/docs/user-guide/containers.html"
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---
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{% capture overview %}
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In the configuration file for a Container, you can set the `command` and `args`
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fields to override the default Entrypoint and Cmd of the the Container's image.
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{% endcapture %}
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{% capture body %}
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## Container entry points and arguments
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The configuration file for a Container has an `image` field that specifies
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the Docker image to be run in the Container. A Docker image has metadata that includes
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a default Entrypoint and a default Cmd.
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When Kubernetes starts a Container, it runs the image's default Entrypoint and
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passes the image's default Cmd as arguments.
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If you want override the image's default Entrypoint and Cmd, you can use the
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`command` and `args` fields in the Container's configuration.
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* The `command` field specifies the actual command run by the Container.
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* The `args` field specifies the arguments passed to the command.
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This table summarizes the field names used by Docker and Kubernetes.
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| Description | Docker field name | Kubernetes field name |
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|----------------------------------------|------------------------|-----------------------|
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| The command run by the container | Entrypoint | command |
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| The arguments passed to the command | Cmd | args |
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Here's an example of a configuration file for a Pod that has one Container.
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{% include code.html language="yaml" file="commands.yaml" ghlink="/docs/concepts/configuration/commands.yaml" %}
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When Kubernetes starts the Container, it runs this command:
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```shell
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printenv HOSTNAME KUBERNETES_PORT
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```
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When you override the default Entrypoint and Cmd, these rules apply:
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* If you do not supply `command` or `args` for a Container, the defaults defined
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in the Docker image are used.
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* If you supply a `command` but no `args` for a Container, only the supplied
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`command` is used. The default EntryPoint and the default Cmd defined in the Docker
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image are ignored.
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* If you supply only `args` for a Container, the default Entrypoint defined in
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the Docker image is run with the `args` that you supplied.
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* If you supply a `command` and `args`, the default Entrypoint and the default
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Cmd defined in the Docker image are ignored. Your `command` is run with your
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`args`.
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Here are some examples:
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| Image Entrypoint | Image Cmd | Container command | Container args | Command run |
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|--------------------|------------------|---------------------|--------------------|------------------|
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| `[/ep-1]` | `[foo bar]` | <not set> | <not set> | `[ep-1 foo bar]` |
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| `[/ep-1]` | `[foo bar]` | `[/ep-2]` | <not set> | `[ep-2]` |
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| `[/ep-1]` | `[foo bar]` | <not set> | `[zoo boo]` | `[ep-1 zoo boo]` |
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| `[/ep-1]` | `[foo bar]` | `[/ep-2]` | `[zoo boo]` | `[ep-2 zoo boo]` |
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{% endcapture %}
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{% capture whatsnext %}
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* [Defining a Command and Arguments for a Container](/docs/tasks/configure-pod-container/define-command-argument-container/)
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* [Getting a Shell to a Running Container](/docs/tasks/kubectl/get-shell-running-container/)
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* [Container](/docs/api-reference/v1.6/#container-v1-core)
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* [Docker Entrypoint field](https://docs.docker.com/engine/reference/builder/)
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{% endcapture %}
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{% include templates/concept.md %}
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@ -1,8 +1,8 @@
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---
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title: Defining a Command and Arguments for a Container
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redirect_from:
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- "/docs/tasks/configure-pod-container/define-command-argument-container/"
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- "/docs/tasks/configure-pod-container/define-command-argument-container.html"
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- "/docs/concepts/configuration/container-command-args/"
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- "/docs/concepts/configuration/container-command-arg.html"
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---
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{% capture overview %}
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@ -33,8 +33,7 @@ you define cannot be changed after the Pod is created.
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The command and arguments that you define in the configuration file
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override the default command and arguments provided by the container image.
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If you define args, but do not define a command, the default command is used
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with your new arguments. For more information, see
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[Commands and Capabilities](/docs/user-guide/containers/).
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with your new arguments.
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In this exercise, you create a Pod that runs one container. The configuration
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file for the Pod defines a command and two arguments:
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@ -93,6 +92,41 @@ script. To run your command in a shell, wrap it like this:
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command: ["/bin/sh"]
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args: ["-c", "while true; do echo hello; sleep 10;done"]
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## Notes
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This table summarizes the field names used by Docker and Kubernetes.
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| Description | Docker field name | Kubernetes field name |
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|----------------------------------------|------------------------|-----------------------|
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| The command run by the container | Entrypoint | command |
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| The arguments passed to the command | Cmd | args |
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When you override the default Entrypoint and Cmd, these rules apply:
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* If you do not supply `command` or `args` for a Container, the defaults defined
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in the Docker image are used.
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* If you supply a `command` but no `args` for a Container, only the supplied
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`command` is used. The default EntryPoint and the default Cmd defined in the Docker
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image are ignored.
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* If you supply only `args` for a Container, the default Entrypoint defined in
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the Docker image is run with the `args` that you supplied.
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* If you supply a `command` and `args`, the default Entrypoint and the default
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Cmd defined in the Docker image are ignored. Your `command` is run with your
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`args`.
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Here are some examples:
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| Image Entrypoint | Image Cmd | Container command | Container args | Command run |
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|--------------------|------------------|---------------------|--------------------|------------------|
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| `[/ep-1]` | `[foo bar]` | <not set> | <not set> | `[ep-1 foo bar]` |
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| `[/ep-1]` | `[foo bar]` | `[/ep-2]` | <not set> | `[ep-2]` |
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| `[/ep-1]` | `[foo bar]` | <not set> | `[zoo boo]` | `[ep-1 zoo boo]` |
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| `[/ep-1]` | `[foo bar]` | `[/ep-2]` | `[zoo boo]` | `[ep-2 zoo boo]` |
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{% endcapture %}
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{% capture whatsnext %}
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