hashicorp/packer · error

Environment variable not in format 'key=value': %s

Error message

Environment variable not in format 'key=value': %s

What it means

The shell provisioner validates that every entry in the vars configuration is in 'key=value' form, since each is later exported as an environment variable on the guest. An entry with no '=' or an empty key fails validation and is collected into Prepare's error list.

Source

Thrown at provisioner/shell/provisioner.go:179

			errors.New("Either a script file or inline script must be specified."))
	} else if len(p.config.Scripts) > 0 && p.config.Inline != nil {
		errs = packersdk.MultiErrorAppend(errs,
			errors.New("Only a script file or an inline script can be specified, not both."))
	}

	for _, path := range p.config.Scripts {
		if _, err := os.Stat(path); err != nil {
			errs = packersdk.MultiErrorAppend(errs,
				fmt.Errorf("Bad script '%s': %s", path, err))
		}
	}

	// Do a check for bad environment variables, such as '=foo', 'foobar'
	for _, kv := range p.config.Vars {
		vs := strings.SplitN(kv, "=", 2)
		if len(vs) != 2 || vs[0] == "" {
			errs = packersdk.MultiErrorAppend(errs,
				fmt.Errorf("Environment variable not in format 'key=value': %s", kv))
		}
	}

	if errs != nil && len(errs.Errors) > 0 {
		return errs
	}

	return nil
}

func (p *Provisioner) Provision(ctx context.Context, ui packersdk.Ui, comm packersdk.Communicator, generatedData map[string]interface{}) error {
	if generatedData == nil {
		generatedData = make(map[string]interface{})
	}
	p.generatedData = generatedData

	scripts := make([]string, len(p.config.Scripts))
	copy(scripts, p.config.Scripts)

View on GitHub (pinned to eb36e3c3e4)

Solutions

1. Rewrite each vars entry as KEY=value with a non-empty key.
2. Values may contain '='; only the first '=' separates key and value — ensure the key part before it is valid.
3. Remove empty or placeholder strings from the vars array.
4. If you meant host environment variables, interpolate them in the template (e.g. HCL2 ${env.VAR}) instead of putting bare names in vars.

Example fix

// before
"vars": ["MY_VAR", "=oops"]
// after
"vars": ["MY_VAR=value"]

# shell: every vars entry must match key=value with a non-empty key
for kv in $VARS; do echo "$kv" | grep -qE '^[^=]+=.*' || echo "bad var: $kv"; done

When it happens

Trigger: vars contains entries like 'foo' (no =), '=value' (empty key), or whitespace/empty strings in the Vars list.

Common situations: Passing env var names only (assuming Packer reads them from the host); quoting mistakes in JSON/HCL that drop the '='; building vars arrays programmatically and including empty elements; values containing '=' are fine (SplitN with limit 2), but keys with spaces or leading '=' are not.

Related errors

• Bad script '%s': %s
• ErrInvalidCompressionLevel
• Error parsing target template: %s
• error parsing output_dir template: %w
• signer and key must match when both are set

AI-assisted analysis of hashicorp/packer@eb36e3c3e4 (2026-09-05). Data as JSON: /api/errors/f02fde27cdfcebd9. Report an issue: GitHub.