# Templates

A template is a reusable Remote Dev Environment configuration. Define the machine and its setup once, then create consistent sessions from it without repeating the same choices each time.

## Template overview 

A template can include:

- A stack, a machine type, and a working directory that terminals start in.
- Lifecycle hooks: setup scripts that run when the session is created, when someone gets it, and after every restore.
- Variables and inputs for the values your environment needs.
- Workspace links: shortcut buttons that open a specific folder in your IDE.
- A virtual device: an iOS simulator or Android emulator that every session created from the template boots.

## Lifecycle hooks

A template sets up its sessions with [lifecycle hooks](/bitrise-rde/configuration/lifecycle-hooks). Each hook is a Bash script that runs as the session user, at one moment in the session's life:

- **On create** runs once, when the session is created. Use it for slow, one-time setup, such as cloning and installing dependencies.
- **On claim** runs when the session is assigned to someone. Use it for that person's own setup.
- **On restore** runs every time a stopped session is restored. Use it to restart services.

Every hook is optional. Templates created before lifecycle hooks have a warmup script and a startup script instead. They keep working, and you can [convert them](/bitrise-rde/configuration/lifecycle-hooks#converting-a-template-with-warmup-and-startup-scripts).

## Variables and inputs

Templates carry two kinds of values:

- Variables are stored on the template, with the same value for every session. Mark a variable as secret to encrypt it at rest, or as protected to also make it write-only.
- Inputs are filled in for each session. You can mark an input as required and give it a default value. An input can also pull its value from a [saved input](/bitrise-rde/configuration/saved-inputs), so secrets are resolved on the server and never shown in the UI.

Every variable and input belongs to a scope: Shared values reach every hook, and a hook's own values reach only that hook. Switch on **Also in terminal** to also make a value available in the session's terminal. See [Variables and inputs](/bitrise-rde/configuration/lifecycle-hooks#variables-and-inputs).

## Workspace links

Workspace links are buttons on the session that open a given folder path in your IDE. They're handy for jumping straight into the right directory in a multi-folder project.

## Declared device

A template can declare a virtual device, so every session created from it boots an iOS simulator or Android emulator without any device settings on the session. Turn on **Boot a device with every session** in the template form, or use the CLI:

```bash
bitrise-cli rde template create --file template.json --device-platform ios --device-model "iPhone 16"
```

The template's stack and machine type must fit the platform: a macOS stack for iOS, a Linux Android stack for Android. When you create a session from the template, you can keep the device as declared, change individual fields for that session only, or turn it off with **Start an iOS simulator** or **Start an Android emulator** in the UI and `--no-device` in the CLI. Sessions already created from the template keep the device they were created with. The device options themselves are described in [Device sessions](/bitrise-rde/devices/device-sessions#device-options).

## Managing templates

Create, edit, clone, and delete templates from the [Bitrise RDE UI](/bitrise-rde/rde-options/bitrise-rde-ui), or from the CLI with `bitrise-cli rde template`.

When you create a session, its template configuration is captured as a snapshot. Editing or deleting a template afterwards doesn't change or break sessions that were already created from it. This includes the hooks: a restore, running a failed hook again, and **Rebuild** all use the scripts the session was created with. To use a fixed script, create a new session.

## Warm pools

To have sessions of a template ready before anyone asks for them, create a [warm pool](/bitrise-rde/configuration/warm-pools) from it: **Create warm pool** on the template's page opens the pool form with the template selected. A pool follows its template, so editing the template replaces the pool's warm sessions, and deleting the template deletes its pools. To write a template that works well in a pool, see [Using hooks with a warm pool](/bitrise-rde/configuration/lifecycle-hooks#using-hooks-with-a-warm-pool).