user1811107 user1811107 - 4 months ago 38
Python Question

AWS Boto3 BASE64 encoding error thrown when invoking client.request_spot_instances method

I am trying to submit a request for an EC2 SPOT instance using boto3 (Environment Python 3.5,Windows 7).
I need to pass the UserData parameter for running initial scripts.

The error I get is
File "C:\Users...\Python\Python35\lib\site-packages\botocore\", line 222, in _make_api_call
raise ClientError(parsed_response, operation_name)
botocore.exceptions.ClientError: An error occurred (InvalidParameterValue) when
calling the
RequestSpotInstances operation: Invalid BASE64 encoding of user data Code

I am following this documentation

If I take the UserData parameter out – everything works well.

I have tried different ways to pass the parameter but I end up with the same.similar errors.

Boto 3 Script

client = session.client('ec2')

myparam = str(base64.b64encode(bytes('yum install -y php', 'utf-8')))

response = client.request_spot_instances(
'ImageId': 'ami-xxxxxx',
'KeyName': 'xxxxx',
'InstanceType': 't1.micro',
'UserData': myparam,
'Monitoring': {
'Enabled': True


I think you shouldn't convert your base64 string to str. Are you using Python 3?


myparam = str(base64.b64encode(bytes('yum install -y php', 'utf-8')))


myparam = base64.b64encode(b'yum install -y php')