Magento 2 Admin url 404 not found

If you create a virtual host in Windows XAMPP server (eg localhost:8081), which points to your magento 2 root, you need to do the following fix, in order to avoid 404 not found, when you access magento admin .

Go to app/code/Magento/Backend/App/Area/FrontNameResolver.php (in line 88)

Replace

$host = isset($_SERVER['HTTP_HOST']) ? $_SERVER['HTTP_HOST'] : '';

With

$host = isset($_SERVER['HTTP_HOST']) ? parse_url($_SERVER['HTTP_HOST'], PHP_URL_HOST) : '';

Magento 2 Custom Module Database Installation Script

When you setup the module at firstime, setup_module table doesn’t have a setup data for your custom module, then the magento system will checks for the setup_version of the module in its module.xml file

<module name="Quadone_Sample" schema_version="0.0.5" setup_version="1.0.0" />

Then it will execute Setup/InstallSchema.php to create installation script.

app/code/Quadone/Sample/Setup/InstallSchema.php

<?php

namespace Quadone\Sample\Setup;

use Magento\Framework\Setup\InstallSchemaInterface;

use Magento\Framework\Setup\ModuleContextInterface;

use Magento\Framework\Setup\SchemaSetupInterface;

class InstallSchema implements InstallSchemaInterface

{

    public function install(SchemaSetupInterface $setup, ModuleContextInterface $context)

    {

                        $connection = $setup->getConnection();

        $setup->startSetup();

        /**

         * Create table ‘quadone_sample'

         */

        $table = $connection->newTable(

            $setup->getTable('quadone_sample')

        )->addColumn(

            'qsample_id',

            \Magento\Framework\DB\Ddl\Table::TYPE_INTEGER,

            null,

            ['identity' => true, 'unsigned' => true, 'nullable' => false, 'primary' => true],

            'Quadone Id'

        )->addColumn(

            'name',

            \Magento\Framework\DB\Ddl\Table::TYPE_TEXT,

            8,

            ['nullable' => false, 'default' => 'default'],

            'Name'

        )->addColumn(

            'email',

            \Magento\Framework\DB\Ddl\Table::TYPE_TEXT,

            50,

            ['nullable' => false, 'default' => 'default'],

            'Email Id'

        );

        $connection->createTable($table);

        $setup->endSetup();

    }

}

Clear the cache and run bin/magento setup:upgrade

Upgrading Schema

Change the setup_version in module.xml

<module name="Quadone_Sample" schema_version="0.0.5" setup_version="2.0.0" />

System will executes the Setup/UpgradeSchema.php

<?php

namespace Quadone\Sample\Setup;

use Magento\Framework\Setup\UpgradeSchemaInterface;

use Magento\Framework\Setup\ModuleContextInterface;

use Magento\Framework\Setup\SchemaSetupInterface;

class UpgradeSchema implements UpgradeSchemaInterface

{

    public function upgrade(SchemaSetupInterface $setup, ModuleContextInterface $context)

    {

            $connection = $setup->getConnection();

        $setup->startSetup();

        if (version_compare($context->getVersion(), '2.0.0', '<')) {

      //2^nd parameter is the modified setup_version in module.xml

            $setup->getConnection()->addColumn(

                $setup->getTable(‘quadone_sample’),

                'age',

                [

                    'type' => \Magento\Framework\DB\Ddl\Table::TYPE_SMALLINT,

                    'unsigned' => true,

                    'nullable' => false,

                    'default' => '0',

                    'comment' => 'Age'

                ]

            );

   }

       $setup->endSetup();

    }

}