Aspera Sync with Basic Token Authorization

Aspera nodes that require access key authentication, such as IBM Aspera on Cloud transfer service (AoCts), can be used as synchronization endpoints by configuring the async database on the node and authenticating the async session with a basic token. A basic token requires a docroot on the server and allows access to all files in the docroot.

On the client, set a location for the Aspera Sync snapshot database by running the following command:
```
# asconfigurator -x "set_node_data;async_db_dir,filepath"
```
On the server, set a docroot for the transfer user.
Log in or SSH into the server and run the following command:
```
# asconfigurator -x "set_user_data;user_name,username;absolute,filepath"
```
Create an Aspera access key.

For AoCts, see https://ibm.ibmaspera.com/helpcenter/transfer-service/managing-access-keys/transfer-service-access-keys.
Create the basic token from the access key ID and secret.
Run the following command to encode the access key ID and secret in base64.
```
# echo -n access_key_id:secret | base64
```
The basic token looks similar to the following:
```
ZGlEZXVGTGNwRzlJWWRzdnhqMFNDcTRtT29oTkpUS3ZwNVEyblJXakRnSUE6YXNwZXJh
```
If the basic token breaks across lines in the output, rerun the command using the -w0 option to remove the line break. For example:
```
# echo -n diDeuFLcpG9IYdsvxj0SCq4mOohNJTKvp5Q2nRWjDgIA:aspera | base64 -w0
```

Run a synchronization, using the basic token.

Run async with the -W option or set the ASPERA_SCP_TOKEN environment variable. For example,

# async -N sync -d /images -r lion@10.0.0.1:/data/images -K push -W "Basic ZGlEZXVGTGNwRzlJWWRzdnhqMFNDcTRtT29oTkpUS3ZwNVEyblJXakRnSUE6YXNwZXJh"