make sure user is root

cmd/rename/main.go

@@ -7,6 +7,7 @@ import (
 	"path"
 	"os"
 	"os/exec"
+	"os/user"
 
 	"git.tilde.town/tildetown/town/towndb"
 )
@@ -88,10 +89,20 @@ func main() {
 		quit("usage: rename username new_username")
 	}
 
-	confirmRename()
 	old_name := os.Args[1]
 	new_name := os.Args[2]
 
+	user, err := user.Current()
+	if err != nil {
+		quit(fmt.Sprintf("couldn't get user info: %v", err))
+	}
+
+	if user.Uid != "0" {
+		quit("must be run as root")
+	}
+
+	confirmRename()
+
 	if err := killUser(old_name); err != nil {
 		quit(fmt.Sprintf("pkill failed: %v", err))
 	}