mirror of https://github.com/docker/docs.git
73 lines
2.4 KiB
Markdown
73 lines
2.4 KiB
Markdown
---
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title: Using lifecycle hooks with Compose
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linkTitle: Use lifecycle hooks
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weight: 20
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desription: How to use lifecycle hooks with Docker Compose
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keywords: cli, compose, lifecycle, hooks reference
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---
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{{< introduced compose 2.30.0 "../releases/release-notes.md#2300" >}}
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## Services lifecycle hooks
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When Docker Compose runs a container, it uses two elements,
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[ENTRYPOINT and COMMAND](https://github.com/manuals//engine/containers/run.md#default-command-and-options),
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to manage what happens when the container starts and stops.
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However, it can sometimes be easier to handle these tasks separately with lifecycle hooks -
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commands that run right after the container starts or just before it stops.
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Lifecycle hooks are particularly useful because they can have special privileges
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(like running as the root user), even when the container itself runs with lower privileges
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for security. This means that certain tasks requiring higher permissions can be done without
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compromising the overall security of the container.
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### Post-start hooks
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Post-start hooks are commands that run after the container has started, but there's no
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set time for when exactly they will execute. The hook execution timing is not assured during
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the execution of the container's `entrypoint`.
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In the example provided:
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- The hook is used to change the ownership of a volume to a non-root user (because volumes
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are created with root ownership by default).
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- After the container starts, the `chown` command changes the ownership of the `/data` directory to user `1001`.
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```yaml
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services:
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app:
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image: backend
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user: 1001
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volumes:
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- data:/data
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post_start:
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- command: chown -R /data 1001:1001
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user: root
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volumes:
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data: {} # a Docker volume is created with root ownership
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```
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### Pre-stop hooks
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Pre-stop hooks are commands that run before the container is stopped by a specific
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command (like `docker compose down` or stopping it manually with `Ctrl+C`).
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These hooks won't run if the container stops by itself or gets killed suddenly.
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In the following example, before the container stops, the `./data_flush.sh` script is
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run to perform any necessary cleanup.
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```yaml
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services:
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app:
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image: backend
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pre_stop:
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- command: ./data_flush.sh
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```
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## Reference information
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- [`post_start`](/reference/compose-file/services.md#post_start)
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- [`pre_stop`](/reference/compose-file/services.md#pre_stop)
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