Terraforming the Oracle Cloud: choosing and using an image family

For a few times now I have presented about “cloud deployments done the cloud way”, sharing lessons learned in the changing world I find myself in. It’s a lot of fun and so far I have been far too busy to blog about things I learned by trial and error. Working with Terraform turned out to be a very good source for blog posts, I’ll put a few of these up in the hope of saving you a few minutes.

This blog post is all about creating Ubuntu images in Oracle Cloud Infrastructure (OCI) using terraform. The technique is equally applicable for other Linux image types though. In case you find this post later using a search engine, here is some version information that might put everything into context:

$ ./terraform version
Terraform v0.11.10
+ provider.null v1.0.0
+ provider.oci v3.7.0

I used the “null” provider to run a few post-installation commands as shown in various terraform examples for OCI. Right now I’m trying to work out if I can’t do the same in a different way. If I am successful you can expect a blog post to follow…

Creating a Ubuntu 18.04 LTS image in OCI

To create the Ubuntu image (or any other image for that matter), I need information about the image family. Documentation about image families in OCI can be found at https://docs.cloud.oracle.com/iaas/images/.

Scrolling down/selecting the entry from the left hand side I found the link to the Ubuntu 18.04 LTS image family. Each supported image has its own documentation link, containing crucial data: an OCID per location. At the time of writing, the latest Ubuntu image was named Canonical-Ubuntu-18.04-2018.11.17-0 and had an image OCID of ocid1.image.oc1.eu-frankfurt-1.aaaa...i57q7bfsa. An OCID is short for Oracle Cloud Identifier and it’s used in many places in OCI. There are different OCIDs for the image depending on location; the (shortened) OCID I just showed you was for Frankfurt.

With the OCID at hand, I can open my favourite code editor and start putting the terraform script together. I create instances in OCI using the oci_core_instance type, documented at the terraform website.

Be careful, many of the references and code examples I found about oci_core_image are written for older versions of the terraform provider. I noticed some attributes used in the examples are deprecated. It might be useful to compare the source code examples against the current documentation

Part of the definition of an oci_core_instance requires the specification of the operating system in the source_details {} section. To create the Ubuntu VM in the Frankfurt region, I have to specify – amongst other things of course – this:

resource "oci_core_instance" "docker_tf_instance" {
    source_details {
        source_type = "image"
        source_id   = "ocid1.image.oc1.eu-frankfurt-1.aaaa..."

The actual OCID is far longer, the example above is shortened for the sake of readability. I didn’t like it wrapping around the text box and thus destroying my layout. Make sure you use the correct OCID ;)

With the information at hand I can create the Ubuntu VM and connect to it using the specified SSH key. Have fun!