First create simple module, refer this link for step by step implementation after that follow the instruction.
Default home page for luma is cms/index/index, so you need to override that controller in order to redirect.
for override the controler add the below content in your app/code/vendor/namespace/etc/di.xml
<?xml version="1.0"?>
<!--
/**
* Copyright © 2015 Magento. All rights reserved.
* See COPYING.txt for license details.
*/
-->
<config xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance" xsi:noNamespaceSchemaLocation="../../../../../lib/internal/Magento/Framework/ObjectManager/etc/config.xsd">
<preference for="Magento\Cms\Controller\Index\Index" type="MyVendor\MyNamespace\Controler\Index\Redirecthome" />
</config>
New Custom Controller: app/code/Vendor/namespace/Controler/Index/Redirecthome.php
<?php
namespace MyVendor\MyNamespace\Controller\Index;
class Redirecthome extends \Magento\Framework\App\Action\Action
{
protected $resultForwardFactory;
public function __construct(
\Magento\Framework\App\Action\Context $context,
\Magento\Framework\Controller\Result\ForwardFactory $resultForwardFactory
) {
$this->resultForwardFactory = $resultForwardFactory;
parent::__construct($context);
}
public function execute($coreRoute = null)
{
$this->_redirect('customer/account/login');
return;
}
}
Now the home page use the above controller instead of default. I have tested it works.
From Admin: It is possible from admin too
Home Page:
store -> configuration -> General -> Web -> Default pages -> here you can chnge **cms** to **customer/account/login**
Redirection
marketing -> url rewrite -> add new url rewrite -> here you can set request path as **cms** and target path as **customer/account/login**