Image Builder AWS AMI step fails: Failed to initialize packer, win_packer_bootstrap_ssh not found

Problem

The Image Builder AWS AMI build step (AWS Image Builder plugin 1.0.1) fails on a self-hosted build agent with one of these errors:

Image build problem: Failed to initialize packer

user_data_file not found: win_packer_bootstrap_ssh
Image build problem: Failed to validate template

The runner downloads and unpacks Packer by itself. Packer does not have to be installed on the agent.

Cause

Two separate defects in plugin 1.0.1:

• Failed to initialize packer happens on Windows build agents only. The runner starts Packer by the bare name packer.exe, with the build checkout directory as the working directory. Windows does not look for the executable in that directory, so packer init fails unless the directory is in PATH. Linux agents start ./packer and are not affected. Tracked in Image Builder AWS AMI on Windows agents: Failed to initialize packer.
• user_data_file not found: win_packer_bootstrap_ssh happens on any build agent when the step has Platform set to Windows and Install TeamCity agent off. The generated template refers to the bootstrap file, but the plugin copies the file only when it installs the agent. Tracked in Windows AMI build: user_data_file not found: win_packer_bootstrap_ssh. Commit daf51a25f730 (AWS Image Builder: configure VCS mirror baking independently from agent installation) fixes it in the plugin source; plugin 1.0.1 does not contain the fix.

Not a cause of these errors:

• AMI builder plugin no longer works due to packer plugins not being distributed via GitHub any more (Amazon Packer plugin distribution) applies only when the generated template requires the Amazon plugin with a broad version constraint, such as version = ">= 1.0.9". A template pinned to version = "= 1.3.9" is not affected.
• ssh_username in the generated template is copied from the step's SSH Username field. A different value means that the template comes from an earlier build, before the field was changed.

Resolution

1. Download the generated template from the build's hidden artifacts: .teamcity/image_builder/image-builder.pkr.hcl. Its ami_name ends with the build number of the build that generated it.
2. If a Windows agent reports Failed to initialize packer, add the build checkout directory to the machine PATH. The runner unpacks Packer there. Restart the agent so that it inherits the change. A customer confirmed that this works. The checkout directory differs per build configuration and can change, so this is a temporary measure. Running the step on a Linux agent also avoids the error.
3. For user_data_file not found: win_packer_bootstrap_ssh, no workaround is confirmed. Do not create the file by hand. A plugin version that contains the fix from Windows AMI build: user_data_file not found: win_packer_bootstrap_ssh is needed.