How to fix 404 error in admin panel

Thanks for your response.  I have gone through the troubleshooting steps in the manual, but it didn’t help.  One question I have regarding that is, in my “pub/ub-tool/index.php” file, I don’t have either of the commented lines mentioned in the Readme manual.  I am still getting the 404 error.  What needs to be debugged?

Hi Mall,
Thanks for your reply.  I was able to fix this, here’s how:
I found that in “\Ubertheme\Ubdatamigration\Block\Index” the “getToolUrl()” function was adding “pub/” into the url.  Because of “pub/” being added, it made the url invalid, and that’s the reason for the 404 error I was getting.
Instead of just editing the core code to remove the “pub/” addition to the url, to follow along with Magento 2 best practice, I added my own module, and created an “after” plugin for “Ubertheme\Ubdatamigration\Block\Index::getToolUrl()” that removed “pub/”.
Here’s what I did:
{{vendor}}/UbMigrationFix/etc/di.xml

<?xml version="1.0"?>
<config xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance" xsi:noNamespaceSchemaLocation="urn:magento:framework:ObjectManager/etc/config.xsd">
  <type name="Ubertheme\Ubdatamigration\Block\Index">
    <plugin name="{{vendor}}_UbMigrationFix::tool_url_fix" type="{{vendor}}\UbMigrationFix\Plugin\ToolUrlEdit"/>
  </type>
</config>

 
{{vendor}}/UbMigrationFix/Plugin/ToolUrlEdit.php

namespace {{vendor}}\UbMigrationFix\Plugin

class ToolUrlEdit
{
    public function afterGetToolUrl(\Ubertheme\Ubdatamigration\Block\Index $subject, $toolUrl)
    {
        if (strpos($toolUrl, "pub/")) {
            $toolUrl = str_replace("pub/", "", $toolUrl);
        }
        return $toolUrl;
    }
}

This fixed the 404 and I was able to migrate the data successfully.  Hope this helps someone else!

@Isaac Phillips  Thanks a lot! You’re fixed works great. This is needed when Magento 2 /pub is served up as the docroot on the apache web server.