Using environment variables for logging and debugging

Sometimes, we need more verbose information about a build to drill down or debug more details about a build environment or failure. Packer has a few very helpful options for this. It’s a bit confusing that Packer debug and log modes are separate functions. With the PACKER_LOG environment variable set to anything, Packer will dump trace output to stderr:

export PACKER_LOG=1

You may also direct it to a file instead of stderr using the PACKER_LOG_FILE environment variable. The PACKER_LOG option gives verbose information about Packer’s internal operation and is compatible with the -machine-readable flag.

Packer’s -debug flag shows similar output, but Packer will pause at each step of the build waiting for someone to hit Enter to continue. The -debug flag is helpful for manual and interactive builds but not for automated builds where nobody is present to hit a Return key. Unfortunately, the -debug and -machine...