Open a port on an existing instance

All the information I can find on opening/closing ports on instances relates to the “Manage Security Group Rules” tab on the DreamCompute admin web interface. But that seems to only relate to how an instance is set up when it is first created.

I want to manage a port or two on an existing instance (for testing self-serving web scripts).

Which leads to two related questions:

1)What settings do the “Manage Security Group Rules” settings impose on an instance? What tool is being used to control access to the working server?

2)What is the recommended way to alter the port access settings on a server instance after it has been created.

I’m not asking for a walk-through tutorial. Just RTFM me or point me in the right direction.


Sorry that this isn’t better documented in our knowledge base! The best manual that exists at this time is this article:

To specifically answer your questions:

  1. Security Group Rules are the primary firewall provided for DreamCompute instances. You can install additional firewalls yourself (fail2ban, etc.), but that’s on you. :slight_smile:

  2. If you want to open/close ports on an instance after it’s been created, you’ll want to use Security Group Rules (I recommend creating a separate/new security group so that you can assign just that group to your instance or add it on to augment the “default” security group).

Hopefully that makes sense / clarifies the situation, but if you have any additional questions, feel free to update this thread or submit a support ticket in the panel!

Not exactly. Security groups are created and applied independently from instance creation. You can create all the security groups you need, based on the network and access architecture you need.

You mention that you’re working with scripts. Depending on the programming language you’re using, you may want to use the OpenStack API from your scripts instead of the web interface to create security groups and apply them to your instances. For example, you can use Ansible or python-openstack on DreamCompute. There is some documentation on DreamHost’s Knowledge Base to get you started and you can expand your search online looking for OpenStack and your favorite programming language. Another useful resource is