> ## Documentation Index
> Fetch the complete documentation index at: https://docs.fly.io/llms.txt
> Use this file to discover all available pages before exploring further.

# Customizing Deployments

The `fly launch` command sets you up with a useful starting point, but you can customize just about everything to meet your needs. Here's a few things that might be useful to know.

## Startup Scripts

The `fly launch` command generated a `.fly/scripts` directory. Any file in here ending in `.sh` will run (via `bash`) anytime your application is started.

These scripts are called from the Docker `ENTRYPOINT` script (`.fly/entrypoint.sh`) before anything else is ran.

By default, `fly launch` generates a startup script `.fly/scripts/caches.sh`, which runs various artisan cache commands such as `config:cache`, `route:cache`, and `view:cache`.

You can enable or disable those as you see fit, as well as add your own `.sh` scripts!

## Release Command

You may want to use the [`release_command`](/reference/configuration#the-deploy-section) to perform database migrations or other tasks. The release command is run in a temporary VM that is created just before your application is deployed and released. Keep in mind that this temporary VM doesn't have access to volumes. This potentially helps with zero-downtime deploys.

Note, however, that any Startup Script in `.fly/scripts` will also be run when a `release_command` is used.

If you need a startup script to do something (or NOT do something) during a release command, your scripts can detect the presence of the `RELEASE_COMMAND` environment variable.

```bash theme={null}
if [ -z "$RELEASE_COMMAND" ]; then
    # We are NOT in a temporary VM, run as normal...
else
    # We are in the temporary VM created
    # for release commands...
fi
```

Note that [release commands](/reference/configuration#the-deploy-section) run in a temporary VM. Any file-based changes done in the release command (such as `artisan view:cache`) will be lost when the release command is completed. The subsequently deployed application is a totally different VM. Commands that result in file-based changes (such as `artisan view:cache`) is best run as a Startup Script.