### Start configurable-http-proxy command line

Source: https://jupyterhub.readthedocs.io/en/stable/howto/separate-proxy.html

Example command to start the configurable-http-proxy as a separate service. Ensure the API IP/port match the hub's configuration and that the default/error targets point to the hub.

```bash
$ configurable-http-proxy --ip=127.0.0.1 --port=8000 --api-ip=127.0.0.1 --api-port=8001 --default-target=http://localhost:8081 --error-target=http://localhost:8081/hub/error

```

--------------------------------

### Install Kernelspecs System-Wide

Source: https://jupyterhub.readthedocs.io/en/stable/_sources/howto/configuration/config-user-env.md.txt

Example commands to install Python 2 and Python 3 kernelspecs system-wide to /usr/local.

```bash
/path/to/python3 -m ipykernel install --prefix=/usr/local
/path/to/python2 -m ipykernel install --prefix=/usr/local
```

--------------------------------

### Spawner.start method example

Source: https://jupyterhub.readthedocs.io/en/stable/reference/spawners.html

Illustrates the typical structure of a Spawner's start method, including environment variable retrieval, command construction, and process initiation.

```python
async def start(self):
    self.ip = '127.0.0.1'
    self.port = random_port()
    # get environment variables,
    # several of which are required for configuring the single-user server
    env = self.get_env()
    cmd = []
    # get jupyterhub command to run,
    # typically ['jupyterhub-singleuser']
    cmd.extend(self.cmd)
    cmd.extend(self.get_args())

    await self._actually_start_server_somehow(cmd, env)
    # url may not match self.ip:self.port, but it could!
    url = self._get_connectable_url()
    return url

```

--------------------------------

### Install Configurable HTTP Proxy Locally

Source: https://jupyterhub.readthedocs.io/en/stable/_sources/contributing/setup.md.txt

Install configurable-http-proxy locally if a global install fails due to permissions. Ensure the local bin directory is added to your PATH.

```bash
npm install configurable-http-proxy
export PATH=$PATH:$(pwd)/node_modules/.bin
```

--------------------------------

### start

Source: https://jupyterhub.readthedocs.io/en/stable/reference/api/proxy.html

Starts the proxy. This method must be defined by subclasses if the proxy is to be started by the Hub.

```APIDOC
## `start`

### Description
Starts the proxy. Will be called during startup if `should_start` is True. This method must be defined by subclasses if the proxy is to be started by the Hub.

### Method
`start()`
```

--------------------------------

### Start Server

Source: https://jupyterhub.readthedocs.io/en/stable/_sources/tutorial/server-api.md.txt

Initiate the launch of a user's server. This endpoint can be used to start the default server or a named server for a given user. The response indicates whether the server is immediately ready or has started the spawning process.

```APIDOC
## POST /hub/api/users/:username/servers/[:servername]

### Description
Starts a server for a given user. If `servername` is omitted, it starts the default server.

### Method
POST

### Endpoint
/hub/api/users/:username/servers/[:servername]

### Parameters
#### Path Parameters
- **username** (string) - Required - The username of the user for whom to start the server.
- **servername** (string) - Optional - The name of the server to start. If omitted, the default server is started.

### Response
#### Success Response (201 Created)
Indicates the launch completed and the server is ready and available immediately.

#### Success Response (202 Accepted)
Indicates the server has begun launching but is not immediately ready. The server will show `pending: 'spawn'` and requires polling or using the progress API to determine readiness.
```

--------------------------------

### Service Configuration Examples

Source: https://jupyterhub.readthedocs.io/en/stable/reference/api/service.html

Examples of how to configure services in JupyterHub, demonstrating both externally managed and hub-managed services.

```APIDOC
An externally managed service running on a URL:
```python
{
    'name': 'my-service',
    'url': 'https://host:8888',
    'admin': True,
    'api_token': 'super-secret',
}
```

A hub-managed service with no URL:
```python
{
    'name': 'cull-idle',
    'command': ['python', '/path/to/cull- বাহ']
    'admin': True,
}
```
```

--------------------------------

### Example Resource Requests and Limits

Source: https://jupyterhub.readthedocs.io/en/stable/_sources/explanation/capacity-planning.md.txt

A sensible starting point for CPU and memory requests and limits in a JupyterHub deployment. Adjust memory based on expected computations like machine learning or data analysis.

```yaml
request:
  cpu: 0.5
  mem: 2G
limit:
  cpu: 1
  mem: 2G
```

--------------------------------

### Spawner Pre-Spawn Hook Example

Source: https://jupyterhub.readthedocs.io/en/stable/reference/api/spawner.html

Implement a pre-spawn hook to perform bootstrapping tasks before a user's server starts. This hook can modify the spawner's environment.

```python
def my_hook(spawner):
    username = spawner.user.name
    spawner.environment["GREETING"] = f"Hello {username}"

c.Spawner.pre_spawn_hook = my_hook
```

--------------------------------

### Start a user's single-user notebook server

Source: https://jupyterhub.readthedocs.io/en/stable/reference/rest-api.html

Starts a user's single-user notebook server. Spawn options can be provided in the request body.

```APIDOC
## Start a user's single-user notebook server

### Description
Starts a user's single-user notebook server. Spawn options can be passed as a JSON body when spawning via the API instead of spawn form. The structure of the options will depend on the Spawner's configuration. The body itself will be available as `user_options` for the Spawner.

### Method
POST

### Endpoint
/hub/api/users/{name}/server

### Parameters
#### Path Parameters
- **name** (string) - Required - username

### Request Body
- **Spawn options** (object) - Optional - Spawn options can be passed as a JSON body when spawning via the API instead of spawn form. The structure of the options will depend on the Spawner's configuration.

### Request Example
```json
{
}
```

### Response
#### Success Response (201)
The user's notebook server has started

#### Success Response (202)
The user's notebook server has not yet started, but has been requested
```

--------------------------------

### Example of a Complete Server Progress Event

Source: https://jupyterhub.readthedocs.io/en/stable/tutorial/server-api.html

Shows a typical final event from the server progress API when a server has successfully started. Includes the server URL and a confirmation message.

```json
{
  "progress": 100,
  "ready": true,
  "message": "Server ready at /user/test-1/",
  "html_message": "Server ready at <a href=\"/user/test-1/\">/user/test-1/</a>",
  "url": "/user/test-1/"
}
```

--------------------------------

### Example of adding a user route

Source: https://jupyterhub.readthedocs.io/en/stable/_sources/howto/proxy.md.txt

This example demonstrates how to add a route for a specific user, including associated user data.

```python
await proxy.add_route('/user/pgeorgiou/', 'http://127.0.0.1:1227',
                {'user': 'pgeorgiou'})
```

--------------------------------

### Install Kernelsystem-wide

Source: https://jupyterhub.readthedocs.io/en/stable/howto/configuration/config-user-env.html

Install Python 2 and Python 3 kernels system-wide using 'ipykernel install' with the --prefix=/usr/local option. This ensures kernels are available to all users.

```bash
/path/to/python3 -m ipykernel install --prefix=/usr/local
/path/to/python2 -m ipykernel install --prefix=/usr/local

```

--------------------------------

### Example Hub-Managed Service Environment Variables

Source: https://jupyterhub.readthedocs.io/en/stable/_sources/reference/services.md.txt

Shows the specific environment variables passed to the 'idle-culler' service example when it is launched by the Hub.

```bash
JUPYTERHUB_SERVICE_NAME: 'idle-culler'
JUPYTERHUB_API_TOKEN: API token assigned to the service
JUPYTERHUB_API_URL: http://127.0.0.1:8080/hub/api
JUPYTERHUB_BASE_URL: https://mydomain[:port]
JUPYTERHUB_SERVICE_PREFIX: /services/idle-culler/
```

--------------------------------

### Install Configurable HTTP Proxy Globally

Source: https://jupyterhub.readthedocs.io/en/stable/_sources/contributing/setup.md.txt

Install the configurable-http-proxy globally using npm. This is required for running and testing the default JupyterHub configuration. If permission errors occur, consider using `sudo` or a local install.

```bash
npm install -g configurable-http-proxy
```

--------------------------------

### Set Server Start Timeout

Source: https://jupyterhub.readthedocs.io/en/stable/reference/config-reference.html

Configure the maximum time in seconds allowed for a single-user server to start. If exceeded, startup is considered failed.

```python
c.SimpleLocalProcessSpawner.start_timeout = 120
```

--------------------------------

### Build and install SELinux module

Source: https://jupyterhub.readthedocs.io/en/stable/_sources/howto/configuration/config-sudo.md.txt

Compile the SELinux policy definition into a module and install it on the system. This is part of the SELinux troubleshooting steps.

```bash
$ checkmodule -M -m -o sudo_exec_selinux.mod sudo_exec_selinux.te
$ semodule_package -o sudo_exec_selinux.pp -m sudo_exec_selinux.mod
$ semodule -i sudo_exec_selinux.pp
```

--------------------------------

### Start JupyterHub for Development

Source: https://jupyterhub.readthedocs.io/en/stable/_sources/contributing/setup.md.txt

Start the JupyterHub service using a development configuration file. This allows you to test your changes locally.

```bash
jupyterhub -f testing/jupyterhub_config.py
```

--------------------------------

### Start a user's named server

Source: https://jupyterhub.readthedocs.io/en/stable/reference/rest-api.html

Starts a user's named server. Spawn options can be provided in the request body.

```APIDOC
## Start a user's named server

### Description
Starts a user's named server. Spawn options can be passed as a JSON body when spawning via the API instead of spawn form. The structure of the options will depend on the Spawner's configuration.

### Method
POST

### Endpoint
/hub/api/users/{name}/servers/{server_name}

### Parameters
#### Path Parameters
- **name** (string) - Required - username
- **server_name** (string) - Required - name given to a named-server (empty string for default server). Note that depending on your JupyterHub infrastructure there are limitations to `server_name`. Default spawner with K8s pod will not allow Jupyter Notebooks to be spawned with a name that contains more than 253 characters (keep in mind that the pod will be spawned with extra characters to identify the user and hub).

### Request Body
- **Spawn options** (object) - Optional - Spawn options can be passed as a JSON body when spawning via the API instead of spawn form. The structure of the options will depend on the Spawner's configuration.

### Request Example
```json
{
}
```

### Response
#### Success Response (201)
The user's notebook named-server has started

#### Success Response (202)
The user's notebook named-server has not yet started, but has been requested
```

--------------------------------

### Tutorial Setup on AWS

Source: https://jupyterhub.readthedocs.io/en/stable/reference/gallery-jhub-deployments.html

This describes a manual setup for spinning up multiple Jupyter Notebooks on AWS for a tutorial. It involves using Docker to create isolated student environments.

```text
* I started a big Amazon machine;
* I installed Docker and built a custom image containing my software of
  interest;
* I ran multiple containers, one connected to port 8000, one on 8001,
  etc. and gave each student a different port;
* students could connect in and use the Terminal program in Jupyter to
  execute commands, and could upload/download files via the Jupyter
  console interface;
* in theory I could have used notebooks too, but for this I didn’t have
  need.

I am aware that JupyterHub can probably do all of this including manage
the containers, but I’m still a bit shy of diving into that; this was
fairly straightforward, gave me disposable containers that were isolated
for each individual student, and worked almost flawlessly.  Should be
easy to do with RStudio too.


```

--------------------------------

### Basic Spawner start method

Source: https://jupyterhub.readthedocs.io/en/stable/_sources/reference/spawners.md.txt

Illustrates a typical implementation of the `Spawner.start` method, including setting IP and port, retrieving environment variables, constructing the command, and initiating the server process.

```python
async def start(self):
    self.ip = '127.0.0.1'
    self.port = random_port()
    # get environment variables,
    # several of which are required for configuring the single-user server
    env = self.get_env()
    cmd = []
    # get jupyterhub command to run,
    # typically ['jupyterhub-singleuser']
    cmd.extend(self.cmd)
    cmd.extend(self.get_args())

    await self._actually_start_server_somehow(cmd, env)
    # url may not match self.ip:self.port, but it could!
    url = self._get_connectable_url()
    return url
```

--------------------------------

### Install Node.js Dependencies

Source: https://jupyterhub.readthedocs.io/en/stable/_sources/contributing/setup.md.txt

Install necessary Node.js dependencies to compile CSS. This is often required if the 'lessc' command is not found during setup.

```bash
npm install
```

--------------------------------

### Install JavaScript Dependencies for LESS Compilation

Source: https://jupyterhub.readthedocs.io/en/stable/contributing/setup.html

If 'lessc' is not found during setup, run this command to install necessary Node.js dependencies for CSS compilation.

```bash
npm install

```

--------------------------------

### Spawner State Management Example

Source: https://jupyterhub.readthedocs.io/en/stable/_sources/reference/spawners.md.txt

Implement methods to get, load, and clear the state for a Spawner, typically used for persisting information like process IDs between server restarts. This example shows how to manage the PID for single-process spawners.

```python
def get_state(self):
    """get the current state"""
    state = super().get_state()
    if self.pid:
        state['pid'] = self.pid
    return state
```

```python
def load_state(self, state):
    """load state from the database"""
    super().load_state(state)
    if 'pid' in state:
        self.pid = state['pid']
```

```python
def clear_state(self):
    """clear any state (called after shutdown)"""
    super().clear_state()
    self.pid = 0
```

--------------------------------

### Start a server with POST /hub/api/users/:username/servers/[:servername]

Source: https://jupyterhub.readthedocs.io/en/stable/_sources/tutorial/server-api.md.txt

Initiate the launch of a user's server using a POST request. A '201 Created' response means the server is ready immediately, while '202 Accepted' indicates it has started spawning and requires further waiting.

```bash
POST /hub/api/users/:username/servers/[:servername]
```

--------------------------------

### Start a Server with POST Request

Source: https://jupyterhub.readthedocs.io/en/stable/tutorial/server-api.html

Initiate the launch of a user's server by making a POST request to the specified API endpoint. This action requires the 'servers' scope.

```bash
POST /hub/api/users/:username/servers/[:servername]

```

--------------------------------

### Get Service by Name Response

Source: https://jupyterhub.readthedocs.io/en/stable/reference/rest-api.html

Example response when retrieving a specific service by its name. Provides detailed information about the service.

```json
{
  "name": "string",
  "kind": "service",
  "admin": true,
  "roles": [
    "string"
],
  "url": "string",
  "prefix": "string",
  "pid": 0,
  "command": [
    "string"
],
  "info": { }

}
```

--------------------------------

### Example Spawned Command

Source: https://jupyterhub.readthedocs.io/en/stable/_sources/reference/spawners.md.txt

Illustrates the resulting command-line execution after applying Spawner.cmd and Spawner.args configurations.

```bash
my-singleuser-wrapper --debug --flag
```

--------------------------------

### Troubleshoot JupyterHub Deployment

Source: https://jupyterhub.readthedocs.io/en/stable/faq/troubleshooting.html

Run this command to get detailed information about installed packages, versions, and system configuration for troubleshooting.

```bash
jupyter troubleshoot

```

--------------------------------

### Spawner.start Method

Source: https://jupyterhub.readthedocs.io/en/stable/_sources/reference/spawners.md.txt

The `Spawner.start` method is responsible for initiating a single-user server for a given user. It should return the `(ip, port)` of the running server or a full URL. The example demonstrates how to construct the command and environment variables for the server process.

```APIDOC
## Spawner.start

### Description
Starts a single-user server for a single user. Information about the user is available via `self.user`. The return value should be the `(ip, port)` of the running server, or a full URL as a string.

### Method
`async def start(self)`

### Parameters
None explicitly defined, but relies on instance attributes like `self.user`, `self.ip`, `self.port`, `self.cmd`, and methods like `self.get_env()`, `self.get_args()`, `self._get_connectable_url()`.

### Request Example
```python
async def start(self):
    self.ip = '127.0.0.1'
    self.port = random_port()
    # get environment variables, 
    # several of which are required for configuring the single-user server
    env = self.get_env()
    cmd = []
    # get jupyterhub command to run, 
    # typically ['jupyterhub-singleuser']
    cmd.extend(self.cmd)
    cmd.extend(self.get_args())

    await self._actually_start_server_somehow(cmd, env)
    # url may not match self.ip:self.port, but it could!
    url = self._get_connectable_url()
    return url
```

### Response
- **(ip, port)** or **URL** (string) - The connection details for the running server.

### Response Example
`'http://127.0.0.1:8888'`

### Exception Handling
If `Spawner.start` raises an Exception, a message can be passed to the user via `.jupyterhub_html_message` (rendered as HTML) or `.jupyterhub_message` (rendered as plain text).
```

--------------------------------

### Build and Serve Documentation Locally

Source: https://jupyterhub.readthedocs.io/en/stable/contributing/docs.html

Builds the HTML version of the documentation and serves it locally for preview. This command automatically re-renders HTML upon detecting changes.

```bash
sphinx-autobuild docs/source/ docs/_build/html

```

--------------------------------

### Retrieve User Model via API with Requests

Source: https://jupyterhub.readthedocs.io/en/stable/_sources/reference/services.md.txt

Make a GET request to the /hub/api/user endpoint with an access token in the Authorization header to retrieve the user model. This example uses the requests library.

```python
r = requests.get(
    "http://127.0.0.1:8081/hub/api/user",
    headers = {
        'Authorization' : f'token {api_token}',
    },
)
r.raise_for_status()
user = r.json()
```

--------------------------------

### cmd

Source: https://jupyterhub.readthedocs.io/en/stable/reference/api/spawner.html

The command used for starting the single-user server. This can be a string or a list containing the path to the startup script. Extra arguments should be provided via `args`. Useful for starting servers in different Python environments.

```APIDOC
## c.Spawner.cmd = Command()

The command used for starting the single-user server.
Provide either a string or a list containing the path to the startup script command. Extra arguments, other than this path, should be provided via `args`.
This is usually set if you want to start the single-user server in a different python environment (with virtualenv/conda) than JupyterHub itself.
Some spawners allow shell-style expansion here, allowing you to use environment variables. Most, including the default, do not. Consult the documentation for your spawner to verify!
```

--------------------------------

### Install JupyterHub with conda

Source: https://jupyterhub.readthedocs.io/en/stable/_sources/tutorial/quickstart.md.txt

Install JupyterHub and its proxy using conda. Also installs JupyterLab and notebook if needed for the same environment.

```bash
conda install -c conda-forge jupyterhub  # installs jupyterhub and proxy
conda install jupyterlab notebook  # needed if running the notebook servers in the same environment
```

--------------------------------

### Example of Spawned Command

Source: https://jupyterhub.readthedocs.io/en/stable/reference/spawners.html

Illustrates the resulting command-line string after applying `Spawner.cmd` and `Spawner.args` configuration.

```bash
my-singleuser-wrapper --debug --flag

```

--------------------------------

### Install and Install Hooks for Pre-commit

Source: https://jupyterhub.readthedocs.io/en/stable/contributing/tests.html

Install the pre-commit package and register git hooks to automatically check code formatting before commits.

```bash
pip install pre-commit
pre-commit install --install-hooks

```

--------------------------------

### Example route structure

Source: https://jupyterhub.readthedocs.io/en/stable/howto/proxy.html

Illustrates the expected dictionary format for routes when retrieved via `get_all_routes`.

```json
{
  '/proxy/path/': {
    'routespec': '/proxy/path/',
    'target': 'http://...',
    'data': {},
  },
}


```

--------------------------------

### Install Node.js and npm on Debian/Ubuntu

Source: https://jupyterhub.readthedocs.io/en/stable/_sources/tutorial/quickstart.md.txt

Use this command to install Node.js and npm on Debian/Ubuntu systems if you are using pip for JupyterHub installation.

```bash
sudo apt-get install nodejs npm
```

--------------------------------

### Start Configurable HTTP Proxy

Source: https://jupyterhub.readthedocs.io/en/stable/_sources/howto/separate-proxy.md.txt

This command starts the configurable-http-proxy. Ensure `--api-ip` and `--api-port` match the hub's `ConfigurableHTTPProxy.api_url`. `--default-target` and `--error-target` should point to the hub.

```bash
$ configurable-http-proxy --ip=127.0.0.1 --port=8000 --api-ip=127.0.0.1 --api-port=8001 --default-target=http://localhost:8081 --error-target=http://localhost:8081/hub/error
```

--------------------------------

### Install JupyterHub with pip and npm

Source: https://jupyterhub.readthedocs.io/en/stable/_sources/tutorial/quickstart.md.txt

Install JupyterHub and the configurable-http-proxy using pip and npm. Also installs JupyterLab and notebook if needed for the same environment.

```bash
python3 -m pip install jupyterhub
npm install -g configurable-http-proxy
python3 -m pip install jupyterlab notebook  # needed if running the notebook servers in the same environment
```

--------------------------------

### Install Node.js/npm on Linux (Debian/Ubuntu)

Source: https://jupyterhub.readthedocs.io/en/stable/tutorial/quickstart.html

Install Node.js and npm using the system's package manager. This is a prerequisite for JupyterHub installation if not using conda.

```bash
sudo apt-get install nodejs npm

```

--------------------------------

### Install Documentation Build Dependencies

Source: https://jupyterhub.readthedocs.io/en/stable/contributing/docs.html

Installs the necessary Python packages for building JupyterHub's documentation locally. Ensure you have Python and Git installed.

```bash
python3 -m pip install -r docs/requirements.txt
python3 -m pip install sphinx-autobuild

```

--------------------------------

### Spawner Options Form Example

Source: https://jupyterhub.readthedocs.io/en/stable/reference/api/spawner.html

An example of an HTML form that can be used to allow users to specify options when launching their server. The data from this form is passed to the spawner.

```html
Set your key:
<input name="key" val="default_key"></input>
<br>
Choose a letter:
<select name="letter" multiple="true">
  <option value="A">The letter A</option>
  <option value="B">The letter B</option>
</select>


```

--------------------------------

### Install Python Package System-Wide

Source: https://jupyterhub.readthedocs.io/en/stable/_sources/howto/configuration/config-user-env.md.txt

Use pip to install Python packages system-wide for all users. Ensure the installation location is readable and executable by users.

```bash
sudo python3 -m pip install numpy
```

--------------------------------

### Configure User Creation Command

Source: https://jupyterhub.readthedocs.io/en/stable/reference/api/auth.html

Specify the command and arguments for creating new system users. The USERNAME placeholder will be replaced with the actual username. This example shows how to set a custom home directory.

```python
c.LocalAuthenticator.add_user_cmd = [
    'adduser',
    '-q',
    '--gecos',
    '""',
    '--home',
    '/customhome/USERNAME',
    '--disabled-password'
]
```

--------------------------------

### Spawner.start()

Source: https://jupyterhub.readthedocs.io/en/stable/reference/api/spawner.html

Asynchronously starts the single-user server. Returns the IP address and port where the Hub can connect to the server.

```APIDOC
## Spawner.start()

### Description
Start the single-user server.

### Returns
- (str, int): The (ip, port) where the Hub can connect to the server.

### Changed in version 0.7
Return ip, port instead of setting on self.user.server directly.
```

--------------------------------

### List Installed Kernelspecs

Source: https://jupyterhub.readthedocs.io/en/stable/_sources/howto/configuration/config-user-env.md.txt

Command to list the locations of all installed Jupyter kernelspecs.

```bash
jupyter kernelspec list
```

--------------------------------

### Test JupyterHub Installation

Source: https://jupyterhub.readthedocs.io/en/stable/tutorial/quickstart.html

Verify the installation of JupyterHub and configurable-http-proxy by checking their help outputs.

```bash
jupyterhub -h
configurable-http-proxy -h

```

--------------------------------

### Full Authenticator Skeleton Example

Source: https://jupyterhub.readthedocs.io/en/stable/reference/authenticators.html

A comprehensive example demonstrating how to structure an Authenticator class, including backporting `allow_all`, defining restrictive configuration checks in `check_blocked_users`, and permissive configuration checks in `check_allowed`.

```python
class MyAuthenticator(Authenticator):
    # backport allow_all for compatibility with JupyterHub < 5
    allow_all = Bool(False, config=True)
    require_something = List(config=True)
    allowed_something = Set()

    def authenticate(self, data, handler):
        ...
        if success:
            return {"username": username, "auth_state": {...}}
        else:
            return None

    def check_blocked_users(self, username, authentication=None):
        """Apply _restrictive_ configuration"""

        if self.require_something and not has_something(username, self.request_):
            return False
        # repeat for each restriction
        if restriction_defined and restriction_not_met:
            return False
        return super().check_blocked_users(self, username, authentication)

    def check_allowed(self, username, authentication=None):
        """Apply _permissive_ configuration

        Only called if check_blocked_users returns True
        AND allow_all is False
        """
        if self.allow_all:
            # check here to backport allow_all behavior
            # from JupyterHub 5
            # this branch will never be taken with jupyterhub >=5
            return True
        if self.allowed_something and user_has_something(username):
            return True
        # repeat for each allow
        if allow_config and allow_met:
            return True
        # should always have this at the end
        if self.allowed_users and username in self.allowed_users:
            return True
        # do not call super!
        # super().check_allowed is not safe with JupyterHub < 5.0,
        # as it will return True if allowed_users is empty
        return False

```

--------------------------------

### Configure LocalProcessSpawner command

Source: https://jupyterhub.readthedocs.io/en/stable/reference/config-reference.html

Set the command used for starting the single-user server. Provide a string or a list containing the path to the startup script. Extra arguments should be passed via `args`. This is typically used for starting servers in different Python environments.

```python
c.LocalProcessSpawner.cmd = "/path/to/jupyterhub-singleuser"
```

```python
c.LocalProcessSpawner.cmd = ["/usr/bin/env", "python", "-m", "jupyterhub_singleuser"]
```

--------------------------------

### Configure PAM Authenticator User Creation Command

Source: https://jupyterhub.readthedocs.io/en/stable/reference/config-reference.html

Specify the command and arguments for creating new users with PAM. This example shows how to set a custom home directory for new users.

```python
c.PAMAuthenticator.add_user_cmd = [
    'adduser',
    '-q',
    '--gecos',
    '""',
    '--home',
    '/customhome/USERNAME',
    '--disabled-password'
]
```

--------------------------------

### Install jupyterhub-idle-culler

Source: https://jupyterhub.readthedocs.io/en/stable/tutorial/getting-started/services-basics.html

Install the jupyterhub-idle-culler package using pip. This is the first step to configuring it as a Hub-managed service.

```bash
pip install jupyterhub-idle-culler

```

--------------------------------

### Test JupyterHub and proxy installation

Source: https://jupyterhub.readthedocs.io/en/stable/_sources/tutorial/quickstart.md.txt

Verify that JupyterHub and configurable-http-proxy are installed correctly by checking their help messages.

```bash
jupyterhub -h
configurable-http-proxy -h
```

--------------------------------

### Build Frontend Components (Admin Page)

Source: https://jupyterhub.readthedocs.io/en/stable/contributing/setup.html

Navigate to the 'jsx' directory and run these commands to install dependencies and continuously rebuild the admin page as you make changes. Requires a refresh of the browser.

```bash
cd jsx
npm install
npm run build:watch

```

--------------------------------

### Spawner Configuration Options

Source: https://jupyterhub.readthedocs.io/en/stable/reference/api/spawner.html

Example of Spawner configuration settings, including checkbox and multi-select options.

```yaml
"checked": ["on"], # checkbox
    "multi-select": ["a", "b"],
}
```