# Deno build process


## Build process overview

Zerops starts a temporary build container and performs the following actions:

1. **Installs the build environment** - Sets up base system and Deno runtime
2. **Downloads your application source code** - From [GitHub ↗](https://www.github.com), [GitLab ↗](https://www.gitlab.com) or via [Zerops CLI](/references/cli)
3. **Optionally customizes the build environment** - Runs prepare commands if configured
4. **Runs the build commands** - Executes your build process
5. **Uploads the application artifact** - Stores build output to internal Zerops storage
6. **Caches selected files** - Preserves specified files for faster future builds

The build container is automatically deleted after the build has finished or failed.

## Build configuration

Configure your Deno build process in your `zerops.yaml` file according to the [full build & deploy Deno pipeline guide](/deno/how-to/build-pipeline).

## Build environment

### Default Deno build environment

The default Deno build environment contains:

- <span>Ubuntu 24.04</span>
- Selected version of Deno defined in `zerops.yaml` [build.base](/deno/how-to/build-pipeline#base) parameter
- [zCLI](/references/cli), Zerops command line tool
- Deno and Git

### Customize build environment

To install additional packages or tools, add one or more [build.prepareCommands](/deno/how-to/build-pipeline#preparecommands) to your `zerops.yaml`.

:::info
The application code is available in the `/var/www` folder in your build container before the prepare commands are triggered. This allows you to use any file from your application code in your prepare commands (e.g. a configuration file).
:::

### Build hardware resources

All runtime services use the same hardware resources for build containers:

<table className="w-fit my-1.5">
  <thead>
    <tr className="text-center rounded-lg">
      <th className="w-fit"><strong>HW resource</strong></th>
      <th className="w-fit"><strong>Minimum</strong></th>
      <th className="w-fit"><strong>Maximum</strong></th>
    </tr>
  </thead>
  <tbody>
    <tr>
      <td className="w-fit font-semibold">CPU cores</td>
      <td className="w-fit">1</td>
      <td className="w-fit">5</td>
    </tr>
    <tr>
      <td className="w-fit font-semibold">RAM</td>
      <td className="w-fit">8 GB</td>
      <td className="w-fit">8 GB</td>
    </tr>
    <tr>
      <td className="w-fit font-semibold">Disk</td>
      <td className="w-fit">1 GB</td>
      <td className="w-fit">100 GB</td>
    </tr>
  </tbody>
</table>

Build containers start with minimum resources and scale vertically up to maximum capacity as needed.

:::info
Build container resources are not charged separately. Limited build time is included in your [project core plan](/company/pricing#project-core-plans), with additional build time available if needed.
:::

### Build time limit

The time limit for the whole build pipeline is **1 hour**. After 1 hour, Zerops will terminate the build pipeline and delete the build container.

## Troubleshooting Deno builds

### Build command failures

If any [build command](/deno/how-to/build-pipeline#buildcommands) fails (returns non-zero exit code), the build is canceled. Check the [build log](/deno/how-to/logs#build-log) to troubleshoot the error.

For Deno, if the error log doesn't contain specific error messages, try running your build with verbose output:

```yaml
buildCommands:
  - deno cache main.ts
  - deno compile --allow-net --allow-read main.ts
```

### Prepare command failures

If any [prepare command](/deno/how-to/build-pipeline#preparecommands) fails, check the [build log](/deno/how-to/logs#build-log) for specific error messages. Common issues include:

- Missing permissions in Deno commands (add --allow-net, --allow-read, etc.)
- Ubuntu package installation failures (use sudo apt-get update first)
- Deno cache directory permissions

### Build cache issues

If you encounter unexpected build behavior or dependency issues, the problem might be related to [cached build data](/features/build-cache). While Zerops maintains the build cache to speed up deployments, sometimes you may need to start fresh.

To invalidate the build cache:

1. Go to your service detail in Zerops GUI
2. Choose **Pipelines & CI/CD Settings** from the left menu
3. Click on the **Invalidate build cache** button

This will force Zerops to run the next build clean, including all prepare commands. Learn more about [build cache behavior](/features/build-cache).

:::tip Advanced troubleshooting
For complex build issues that require investigation, you can enable [debug mode](/features/debug-mode) to pause the build process at specific points and inspect the build container state interactively.
:::

## More resources

For more details about the build and deploy pipeline, including how to cancel builds and manage application versions, see the [general pipeline documentation](/features/pipeline).

## Next steps

- Understand the [deployment process](/deno/how-to/deploy-process)
- Learn how to [customize the runtime environment](/deno/how-to/customize-runtime)
- Explore [build and runtime logs](/deno/how-to/logs)