packer fmt: Usage & Common CI Errors

Canonical formatting for your Packer HCL2 templates.

packer fmt rewrites .pkr.hcl and .pkrvars.hcl files to the canonical HCL2 style. As a CI check it keeps template diffs clean and reviews focused on substance.

What it does

packer fmt applies standard HCL2 formatting - consistent indentation and alignment - to Packer template files. By default it edits files in place; with -check it only reports whether files are already formatted and exits nonzero if not.

Common usage

Terminal

# Format files in place
packer fmt .

# Recurse into subdirectories
packer fmt -recursive .

# CI gate: fail if anything is unformatted, show the diff
packer fmt -check -diff -recursive .

Common error in CI: fmt -check fails the build

A formatting gate exits nonzero and lists files that "would be formatted", but applies no change - -check never writes. Fix: run packer fmt -recursive . locally, commit the result, and push. To auto-fix in a pre-commit hook instead of failing CI, drop -check and let fmt write in place.

Key options

Option	Purpose
-check	Exit nonzero if not formatted (no writes)
-diff	Show the formatting diff
-recursive	Include subdirectories
-write=false	Do not modify files