SSM / Client / start_session



Initiates a connection to a target (for example, a managed node) for a Session Manager session. Returns a URL and token that can be used to open a WebSocket connection for sending input and receiving outputs.


Amazon Web Services CLI usage: start-session is an interactive command that requires the Session Manager plugin to be installed on the client machine making the call. For information, see Install the Session Manager plugin for the Amazon Web Services CLI in the Amazon Web Services Systems Manager User Guide.

Amazon Web Services Tools for PowerShell usage: Start-SSMSession isn’t currently supported by Amazon Web Services Tools for PowerShell on Windows local machines.

See also: AWS API Documentation

Request Syntax

response = client.start_session(
        'string': [
  • Target (string) –


    The managed node to connect to for the session.

  • DocumentName (string) – The name of the SSM document you want to use to define the type of session, input parameters, or preferences for the session. For example, SSM-SessionManagerRunShell. You can call the GetDocument API to verify the document exists before attempting to start a session. If no document name is provided, a shell to the managed node is launched by default. For more information, see Start a session in the Amazon Web Services Systems Manager User Guide.

  • Reason (string) – The reason for connecting to the instance. This value is included in the details for the Amazon CloudWatch Events event created when you start the session.

  • Parameters (dict) –

    The values you want to specify for the parameters defined in the Session document.

    • (string) –

      • (list) –

        • (string) –

Return type:



Response Syntax

    'SessionId': 'string',
    'TokenValue': 'string',
    'StreamUrl': 'string'

Response Structure

  • (dict) –

    • SessionId (string) –

      The ID of the session.

    • TokenValue (string) –

      An encrypted token value containing session and caller information. This token is used to authenticate the connection to the managed node, and is valid only long enough to ensure the connection is successful. Never share your session’s token.

    • StreamUrl (string) –

      A URL back to SSM Agent on the managed node that the Session Manager client uses to send commands and receive output from the node. Format: wss://ssmmessages.**region****session-id**?stream=(input|output)

      region represents the Region identifier for an Amazon Web Services Region supported by Amazon Web Services Systems Manager, such as us-east-2 for the US East (Ohio) Region. For a list of supported region values, see the Region column in Systems Manager service endpoints in the Amazon Web Services General Reference.

      session-id represents the ID of a Session Manager session, such as 1a2b3c4dEXAMPLE.


  • SSM.Client.exceptions.InvalidDocument

  • SSM.Client.exceptions.TargetNotConnected

  • SSM.Client.exceptions.InternalServerError