authenticate.md

## Authenticate with Earthdata Login

The first step to use NASA Earthdata is to create an account with Earthdata Login, please follow the instructions at [NASA EDL](https://urs.earthdata.nasa.gov/)

Once registered, earthaccess can use environment variables, a `.netrc` file or interactive input from a user to login with NASA EDL.

If a strategy is not especified, env vars will be used first, then netrc and finally user's input.

```py
import earthaccess

auth = earthaccess.login()
```

If you have a .netrc file with your Earthdata Login credentials

```py
auth = earthaccess.login(strategy="netrc")
```

If your Earthdata Login credentials are set as environment variables: EARTHDATA_USERNAME, EARTHDATA_PASSWORD

```py
auth = earthaccess.login(strategy="environment")
```

If you wish to enter your Earthdata Login credentials when prompted with optional persistence to .netrc

```py
auth = earthaccess.login(strategy="interactive", persist=True)
```



### **Authentication**

By default, `earthaccess` with automatically look for your EDL account credentials in two locations:

1. A `~/.netrc` file
2. `EARTHDATA_USERNAME` and `EARTHDATA_PASSWORD` environment variables

If neither of these options are configured, you can authenticate by calling the `earthaccess.login()` method
and manually entering your EDL account credentials.

```python
import earthaccess

earthaccess.login()
```

Note you can pass `persist=True` to `earthaccess.login()` to have the EDL account credentials you enter
automatically saved to a `~/.netrc` file for future use.


Once you are authenticated with NASA EDL you can:

* Get a file from a DAAC using a `fsspec` session.
* Request temporary S3 credentials from a particular DAAC (needed to download or stream data from an S3 bucket in the cloud).
* Use the library to download or stream data directly from S3.
* Regenerate CMR tokens (used for restricted datasets).


### Earthdata User Acceptance Testing (UAT) environment

If your EDL account is authorized to access the User Acceptance Testing (UAT) system,
you can set earthaccess to work with its EDL and CMR endpoints
by setting the `system` argument at login, as follows:

```python
import earthaccess

earthaccess.login(system=earthaccess.UAT)

```