EC2 user data

A simple configuration method is to place all variables in the EC2 UserData. This method requires no additional software or infrastructure and can be entered using the AWS Console GUI, command line tools, AWS SDK, CloudFormation, and most third party deployment tools. However EC2 UserData is not a secure data store, so it should only be used for non-sensitive data.

Making use of the CloudInit feature in CloudFormation allows you to place a minimal 'stub' configuration in EC2 User data and the remaining data in a resource MetaData section in the template. This is significantly more secure and flexible.

In the MarkLogic startup (/sbin/service MarkLogic <command>), the EC2 UserData is read as lines of text, and if the line starts with "MARKLOGIC_" it is parsed as a name=value pair. Each of the name=value pairs is exported to the environment as = . For example, the MARKLOGIC_CLUSTER_NAME user data variable becomes MARKLOGIC_CLUSTER_NAME shell environment variable, but MYNAME=MYVALUE is ignored. Use of the MARKLOGIC_ prefix is a security precaution to avoid users passing in arbitrary system environment variables, such as PATH. Similarly the UserData is parsed and the environment variables explicitly created rather than the text being eval'd so that arbitrary code injection cannot occur.

Any UserData line not starting with MARKLOGIC_ is ignored so users are free to pass in additional name=value pairs in UserData, or to use it in its entirety for other purposes as long as lines do not start with MARKLOGIC_.