111 lines
3.1 KiB
Markdown
111 lines
3.1 KiB
Markdown
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---
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---
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{% capture overview %}
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This page shows how to write and read a Container
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termination message.
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Termination messages provide a way for containers to write
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information about fatal events to a location where it can
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be easily retrieved and surfaced by tools like dashboards
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and monitoring software. In most cases, information that you
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put in a termination message should also be written to
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the general
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[Kubernetes logs](/docs/user-guide/logging/).
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{% endcapture %}
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{% capture prerequisites %}
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{% include task-tutorial-prereqs.md %}
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{% endcapture %}
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{% capture steps %}
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### Writing and reading a termination message
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In this exercise, you create a Pod that runs one container.
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The configuration file specifies a command that runs when
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the container starts.
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{% include code.html language="yaml" file="termination.yaml" ghlink="/docs/tasks/debug-pod-container/termination.yaml" %}
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1. Create a Pod based on the YAML configuration file:
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export REPO=https://raw.githubusercontent.com/kubernetes/kubernetes.github.io/master
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kubectl create -f $REPO/docs/tasks/debug-pod-container/termination.yaml
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In the YAML file, in the `cmd` and `args` fields, you can see that the
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container sleeps for 10 seconds and then writes "Sleep expired" to
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the `/dev/termination-log` file. After the container writes
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the "Sleep expired" message, it terminates.
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1. Display information about the Pod:
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kubectl get pod termination-demo
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Repeat the preceding command until the Pod is no longer running.
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1. Display detailed information about the Pod:
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kubectl get pod --output=yaml
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The output includes the "Sleep expired" message:
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apiVersion: v1
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kind: Pod
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...
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lastState:
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terminated:
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containerID: ...
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exitCode: 0
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finishedAt: ...
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message: |
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Sleep expired
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...
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1. Use a Go template to filter the output so that it includes
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only the termination message:
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```
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{% raw %} kubectl get pod termination-demo -o go-template="{{range .status.containerStatuses}}{{.lastState.terminated.message}}{{end}}"{% endraw %}
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```
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### Setting the termination log file
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By default Kubernetes retrieves termination messages from
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`/dev/termination-log`. To change this to a different file,
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specify a `terminationMessagePath` field for your Container.
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For example, suppose your Container writes termination messages to
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`/tmp/my-log`, and you want Kubernetes to retrieve those messages.
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Set `terminationMessagePath` as shown here:
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apiVersion: v1
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kind: Pod
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metadata:
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name: msg-path-demo
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spec:
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containers:
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- name: msg-path-demo-container
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image: debian
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terminationMessagePath: "/tmp/my-log"
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{% endcapture %}
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{% capture whatsnext %}
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* See the `terminationMessagePath` field in
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[Container](/docs/api-reference/v1/definitions#_v1_container).
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* Learn about [retrieving logs](/docs/user-guide/logging/).
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* Learn about [Go templates](https://golang.org/pkg/text/template/).
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{% endcapture %}
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{% include templates/task.md %}
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