# Adding Steps

You can easily customize the install and build commands with [environment
variables](/config/environment-variables). However, sometimes you can also add
additional steps to your build. This is useful if you want to optimize cache
hits or don't want to affect the automatically generated provider commands.

## Adding a Step

To add a step, you can use the `steps` field in your configuration file.

```json
{
  "$schema": "https://schema.railpack.com",
  "steps": {
    "new-step": {
      "commands": ["echo 'Hello, world!'"]
    },
  }
}
```

The default `inputs` for a new step is:

```json
"inputs": [
  { "step": "packages:mise" }
]
```

This means that the commands will run in the build image with access to Mise and
build apt packages.

If you want to run after a specific provider-generated step, you can specify the
inputs. For example, this will run the `new-step` after the `build` step.

```json
{
  "$schema": "https://schema.railpack.com",
  "steps": {
    "new-step": {
      "inputs": [
        { "step": "build" }
      ],
      "commands": ["echo 'Hello, world!'"]
    },
  }
}
```

## Including the step output in the final image

By default, the entire `/app` directory is included in the final image. You can
customize this by specifying a `deployOutputs` field. For example, this will
include the `dist` directory in the final image.

```json
{
  "$schema": "https://schema.railpack.com",
  "steps": {
    "new-step": {
      "commands": ["echo 'Hello, world!'"],
      "deployOutputs": [
        "dist"
      ]
    },
  }
}
```

_Note: `deployOutputs` is syntactic sugar for adding this layer to the
`deploy.inputs` field. The above example is equivalent to._

```json
{
  "$schema": "https://schema.railpack.com",
  "steps": {
    "new-step": {
      "commands": ["echo 'Hello, world!'"],
      "deployOutputs": []
    },
  },
  "deploy": {
    "inputs": [
      { "step": "new-step", "include": ["dist"] }
    ]
  }
}
```

Setting the `deployOutputs` to an empty array will mean that no files from the
step are included in the final image and therefore no commands will be executed.

## Running commands that affect the runtime image

This is possible, but not recommended. It is instead recommended to use
- `deploy.aptPackages` to install packages that are needed at runtime
- Copy specific files from a step into the runtime image with `deployOutputs`

_Having trouble? [Let us know!](/help)_