make sure we create the temp dir explicitly when we are setting up the config dir in docker. Otherwise, we create it with root later on and it causes permissions failures.

builder/docker/step_temp_dir.go

@@ -3,6 +3,7 @@ package docker
 import (
 	"context"
 	"fmt"
+	"log"
 	"os"
 	"path/filepath"
 
@@ -18,22 +19,32 @@ type StepTempDir struct {
 
 // ConfigTmpDir returns the configuration tmp directory for Docker
 func ConfigTmpDir() (string, error) {
-	if tmpdir := os.Getenv("PACKER_TMP_DIR"); tmpdir != "" {
-		return filepath.Abs(tmpdir)
-	}
 	configdir, err := packer.ConfigDir()
 	if err != nil {
 		return "", err
 	}
+	if tmpdir := os.Getenv("PACKER_TMP_DIR"); tmpdir != "" {
+		// override the config dir with tmp dir. Still stat it and mkdirall if
+		// necessary.
+		fp, err := filepath.Abs(tmpdir)
+		log.Printf("found PACKER_TMP_DIR env variable; setting tmpdir to %s", fp)
+		if err != nil {
+			return "", err
+		}
+		configdir = fp
+	}
+
 	td := filepath.Join(configdir, "tmp")
 	_, err = os.Stat(td)
 	if os.IsNotExist(err) {
+		log.Printf("Creating tempdir in %s", td)
 		if err = os.MkdirAll(td, 0755); err != nil {
 			return "", err
 		}
 	} else if err != nil {
 		return "", err
 	}
+	log.Printf("Set Packer temp dir to %s", td)
 	return td, nil
 }