93 lines
3.9 KiB
Markdown
93 lines
3.9 KiB
Markdown
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---
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title: "Hooks"
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layout: docs
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---
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Velero currently supports executing commands in containers in pods during a backup.
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## Backup Hooks
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When performing a backup, you can specify one or more commands to execute in a container in a pod
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when that pod is being backed up. The commands can be configured to run *before* any custom action
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processing ("pre" hooks), or after all custom actions have been completed and any additional items
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specified by custom action have been backed up ("post" hooks). Note that hooks are _not_ executed within a shell
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on the containers.
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There are two ways to specify hooks: annotations on the pod itself, and in the Backup spec.
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### Specifying Hooks As Pod Annotations
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You can use the following annotations on a pod to make Velero execute a hook when backing up the pod:
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#### Pre hooks
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* `pre.hook.backup.velero.io/container`
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* The container where the command should be executed. Defaults to the first container in the pod. Optional.
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* `pre.hook.backup.velero.io/command`
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* The command to execute. If you need multiple arguments, specify the command as a JSON array, such as `["/usr/bin/uname", "-a"]`
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* `pre.hook.backup.velero.io/on-error`
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* What to do if the command returns a non-zero exit code. Defaults to Fail. Valid values are Fail and Continue. Optional.
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* `pre.hook.backup.velero.io/timeout`
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* How long to wait for the command to execute. The hook is considered in error if the command exceeds the timeout. Defaults to 30s. Optional.
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#### Post hooks
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* `post.hook.backup.velero.io/container`
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* The container where the command should be executed. Defaults to the first container in the pod. Optional.
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* `post.hook.backup.velero.io/command`
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* The command to execute. If you need multiple arguments, specify the command as a JSON array, such as `["/usr/bin/uname", "-a"]`
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* `post.hook.backup.velero.io/on-error`
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* What to do if the command returns a non-zero exit code. Defaults to Fail. Valid values are Fail and Continue. Optional.
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* `post.hook.backup.velero.io/timeout`
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* How long to wait for the command to execute. The hook is considered in error if the command exceeds the timeout. Defaults to 30s. Optional.
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### Specifying Hooks in the Backup Spec
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Please see the documentation on the [Backup API Type][1] for how to specify hooks in the Backup
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spec.
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## Hook Example with fsfreeze
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We are going to walk through using both pre and post hooks for freezing a file system. Freezing the
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file system is useful to ensure that all pending disk I/O operations have completed prior to taking a snapshot.
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We will be using [examples/nginx-app/with-pv.yaml][2] for this example. Follow the [steps for your provider][3] to
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setup this example.
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### Annotations
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The Velero [example/nginx-app/with-pv.yaml][2] serves as an example of adding the pre and post hook annotations directly
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to your declarative deployment. Below is an example of what updating an object in place might look like.
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```shell
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kubectl annotate pod -n nginx-example -l app=nginx \
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pre.hook.backup.velero.io/command='["/sbin/fsfreeze", "--freeze", "/var/log/nginx"]' \
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pre.hook.backup.velero.io/container=fsfreeze \
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post.hook.backup.velero.io/command='["/sbin/fsfreeze", "--unfreeze", "/var/log/nginx"]' \
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post.hook.backup.velero.io/container=fsfreeze
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```
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Now test the pre and post hooks by creating a backup. You can use the Velero logs to verify that the pre and post
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hooks are running and exiting without error.
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```shell
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velero backup create nginx-hook-test
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velero backup get nginx-hook-test
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velero backup logs nginx-hook-test | grep hookCommand
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```
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## Using Multiple Commands
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To use multiple commands, wrap your target command in a shell and separate them with `;`, `&&`, or other shell conditional constructs.
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```shell
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pre.hook.backup.velero.io/command='["/bin/bash", "-c", "echo hello > hello.txt && echo goodbye > goodbye.txt"]'
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```
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[1]: api-types/backup.md
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[2]: https://github.com/vmware-tanzu/velero/blob/v1.3.2/examples/nginx-app/with-pv.yaml
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[3]: cloud-common.md
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