Creating a Docker image in Bamboo using Docker task throws "invalid reference format" exception

Summary

This article talks about the problem seen while creating the Docker image in Bamboo using Docker task and assigning a tag to it. The tag can be either derived using Bamboo variable, branch name, etc or defined manually.

The Docker task while creating the image fails with exception ERROR: invalid tag "" : invalid reference format. 

Environment

Issue was seen on Bamboo 9.2.4 but the solution will be applicable for all supported versions of Bamboo. 

Diagnosis

To diagnose the problem please refer the Viewing a build log and we can see the below error when the docker task fails

Here we are trying to define a tag "releaseBranchTestingVersion1" to the Docker image which is being created ( Please note that this tag contains both lowercase and uppercase letters ) 

Cause

If we read the Docker tag convention page, it mentions not to use uppercase letters in the Docker tag name. 

"The path consists consists of slash-separated components. Each component may contain lowercase letters, digits and separators. A separator is defined as a period, one or two underscores, or one or more hyphens. A component may not start or end with a separator. While the OCI Distribution Specificationopen_in_new supports more than two slash-separated components, most registries only support two slash-separated components."

The problem can occur if any of the above rules are violated with the tag name.

Solution

The current problem was related to using both lowercase and uppercase in the Docker tag, the solution is to just use the lowercase.

As explained earlier tag can be either a branch name, variable name or something manually defined, below are some example on how to convert them from uppercase to lowercase

Before

After