---
title: "Deploy a custom container image"
description: "Deploy your own public Docker image as a Functions function from its Dockerfile, with the architecture, user, and port rules the image must follow."
content_type: "how-to"
product: "functions"
platform: "MyAccount"
url: "/myaccount/functions/how-to/deploy-a-custom-container-image/"
topic: ["create"]
relationships: {"requires":["/myaccount/functions/how-to/create-a-function/"]}
---

# Deploy a custom container image

Run your own Docker image as a function, from a `Dockerfile` that points at the image. Use **Custom
Container Image** when your application has its own framework or runtime that the built-in templates
do not cover. A container function runs on CPU hardware and is billed as a CPU function. See
[Billing](/myaccount/functions/concepts/billing/).

## Before you begin

You need a public Docker image that is built for `linux/amd64` and runs as a non-root user. A
private image, such as one in E2E Container Registry, cannot be used. By default the container must
listen on port 8080.

If your container listens on a different port, add an environment variable with this name, and
set its value to the port number:

```text
__PORT__
```

Functions reserves the name `PORT`, so choose another.

## Write the Dockerfile

With **Custom Container Image**, the editor has two tabs. The `Dockerfile` tab holds the file the
platform builds. The `DOCS.md` tab holds the platform's guidelines for writing that `Dockerfile`.

The template's `Dockerfile` sets the architecture and the non-root user. It reads:

```dockerfile
# Set your desired public base image here in BASE_IMAGE
# ARG BASE_IMAGE=<YOUR-PUBLIC-CONTAINER_IMAGE>
ARG BASE_IMAGE=e2efaasplatform/react-sample
FROM --platform=linux/amd64 ${BASE_IMAGE}

# Do not modify the following configurations
# These ensure the container runs securely as a non-root user
USER 1001

# You can add your custom instructions below this line [Optional]
```

Of the template's lines, change only the BASE_IMAGE line. Set it to the address of your public
image. Keep `USER 1001` as it is: the template marks it "Do not modify". Add your own
instructions below the last comment.

## Create the function

To upload the files as a ZIP instead, include both `Dockerfile` and `DOCS.md`. See
[Upload code as a ZIP](/myaccount/functions/how-to/upload-code-as-a-zip/).

1. In **Create Function**, choose **Custom Container Image**.
2. In the `Dockerfile` tab, set the BASE_IMAGE argument to your image.
3. Fill in the function name and, under **System Configuration**, the memory and timeout, as in
   [Create a function](/myaccount/functions/how-to/create-a-function/).
4. (Optional) If your container listens on a port other than 8080, add the port environment
   variable under **Function Configuration**, set to the port number. See
   [Before you begin](#before-you-begin).
5. (Optional) To keep instances always running, turn on **Enable Dedicated Replica**. See
   [Keep a function ready with dedicated replicas](/myaccount/functions/how-to/keep-a-function-ready-with-dedicated-replicas/).
6. Click **Create**.

The function builds and deploys, then reads **Running** once your container is up.

## Check that the function is running

When the function reads **Running**, its public HTTPS **URL** is ready. Call it to confirm your
container answers. See [Call a function](/myaccount/functions/how-to/call-a-function/).

If the function reads **Failed**, open its page and read the **Build Logs** tab. See
[Troubleshooting Functions](/myaccount/functions/troubleshooting/functions/).

You now have a function running your own container image. To compare it with the built-in
runtimes, see [Runtimes and hardware](/myaccount/functions/concepts/runtimes-and-hardware/).