Outputting information after provisioning a vm with terraform?

Question

I have a set of vm instance I want to provision with terraform.

Each VM will need the information from the previous one in the chain - during setup a unique key is created for a peering app.

Thoughts about the approach:

• read the information from (write to disk) and put it as the single page of a simple web server
• output something using local-exec, remote-exec
• Something else?

That is to say, I need non-standard (where standard is something like an IP address, hostname) output by a service started after provisioning, that I can then pass to later provisioners. It's getting the output that is the issue, not the dependency.

Answer 1

Terraform has in built functionality to maintain dependencies.

Perhaps you can create the keys as separate resources, and then reference them in both linked vm's ?

Or if not maybe the key that is created can be exported in TF ? Then you can reference it in another VM resource, and TF will be smart enough to first build the first one, then the second.

There probably is a TF solution for your problem, without having to hack around too much. Already local-exec is a last resort kind of thing.

Answer 2

FWIW, I ended up stripping all the provisioners out of the terraform, and just built a simple script, the first step of which was to execute the terraform apply, and then did the rest with simple remote script execution over ssh. Ugly, but it worked.