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fix(compose): use CMD-SHELL with || exit 1 in healthcheck examples #24937

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fix(compose): use CMD-SHELL with || exit 1 in healthcheck examples #24937

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e45c54b
docs: add concept diagrams to what-is-a-container page
mohithshuka Mar 19, 2026
8b2ce2a
fix: correct chown argument order in Compose lifecycle hooks example
Apr 27, 2026
008eaf6
fix(compose): use CMD-SHELL with || exit 1 in healthcheck examples
May 1, 2026
8ce7ace
revert: remove unrelated lifecycle and diagram changes from PR scope
May 6, 2026
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4 changes: 4 additions & 0 deletions content/get-started/docker-concepts/the-basics/what-is-a-container.md
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Expand Up @@ -33,6 +33,8 @@ Here's what makes them awesome. Containers are:
- Independent. Each container is independently managed. Deleting one container won't affect any others.
- Portable. Containers can run anywhere! The container that runs on your development machine will work the same way in a data center or anywhere in the cloud!

![Diagram showing three containers (frontend, backend, database) running side by side, each with an isolated filesystem, all sharing the host OS kernel](images/container-architecture.png)

### Containers versus virtual machines (VMs)

Without getting too deep, a VM is an entire operating system with its own kernel, hardware drivers, programs, and applications. Spinning up a VM only to isolate a single application is a lot of overhead.
Expand All @@ -43,6 +45,8 @@ A container is simply an isolated process with all of the files it needs to run.
>
> Quite often, you will see containers and VMs used together. As an example, in a cloud environment, the provisioned machines are typically VMs. However, instead of provisioning one machine to run one application, a VM with a container runtime can run multiple containerized applications, increasing resource utilization and reducing costs.

![Diagram comparing virtual machines (each with a full Guest OS) versus containers (sharing the host kernel with no Guest OS overhead)](images/containers-vs-vms.png)

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Copilot AI May 1, 2026

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This PR is described/titled as a fix to Compose healthcheck examples, but this file adds new diagrams to the container concepts page. Please split these doc+asset additions into a separate PR (or update the PR title/description) so the change set matches the stated intent and is easier to review.

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## Try it out

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4 changes: 2 additions & 2 deletions content/reference/compose-file/services.md
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Expand Up @@ -1069,7 +1069,7 @@ For more information on `HEALTHCHECK`, see the [Dockerfile reference](/reference

```yml
healthcheck:
test: ["CMD", "curl", "-f", "http://localhost"]
test: ["CMD-SHELL", "curl -f http://localhost || exit 1"]
interval: 1m30s
timeout: 10s
retries: 3
Expand All @@ -1085,7 +1085,7 @@ If it's a string, it's equivalent to specifying `CMD-SHELL` followed by that str

```yml
# Hit the local web app
test: ["CMD", "curl", "-f", "http://localhost"]
test: ["CMD-SHELL", "curl -f http://localhost || exit 1"]
```

Using `CMD-SHELL` runs the command configured as a string using the container's default shell
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