Exception printing is disabled by default for security reasons

Your store is running Magento 2, when installing new extensions, setting configuration or even server memory is overload. You may get this error Exception printing is disabled by default for security reasons Magento 2 But you still don’t know exactly what kind of problem out there. Follow this guide to show the full message.

ERROR: There has been an error processing your request

There has been an error processing your request
Exception printing is disabled by default for security reasons.
Error log record number: 1234567890

Like this screenshot

Exception printing is disabled by default for security reasons

Enable Exception printing in Magento 2

It is similar to Magento 1 but it is located in different folder pub/errors

Rename file pub/errors/local.xml.sample to pub/errors/local.xml

See trace result

Exception printing is disabled by default for security reasons Magento 2

You can go to var/report and get the list of error report.

There are similar errors:

a:4:{i:0;s:46:"SQLSTATE[HY000] [1049] Unknown database 'ce21'";i:1;s:4514:"#0 \vendor\magento\zendframework1\library\Zend\Db\Adapter\Pdo\Mysql.php(111): Zend_Db_Adapter_Pdo_Abstract->_connect()
#1 \vendor\magento\framework\DB\Adapter\Pdo\Mysql.php(340): Zend_Db_Adapter_Pdo_Mysql->_connect()
#2 \vendor\magento\zendframework1\library\Zend\Db\Adapter\Abstract.php(861): Magento\Framework\DB\Adapter\Pdo\Mysql->_connect()
#3 \vendor\magento\zendframework1\library\Zend\Db\Adapter\Abstract.php(931): Zend_Db_Adapter_Abstract->quote('1', NULL)
#4 \vendor\magento\framework\DB\Adapter\Pdo\Mysql.php(1363): Zend_Db_Adapter_Abstract->quoteInto('`store`.`store_...', '1', NULL, NULL)
#5 \vendor\magento\zendframework1\library\Zend\Db\Select.php(1007): Magento\Framework\DB\Adapter\Pdo\Mysql->quoteInto('`store`.`store_...', '1', NULL)
#6 \vendor\magento\zendframework1\library\Zend\Db\Select.php(477): Zend_Db_Select->_where('`store`.`store_...', '1', NULL, true)
#7 \vendor\magento\framework\DB\Select.php(115): Zend_Db_Select->where('`store`.`store_...', '1', NULL)
#8 \vendor\magento\framework\Model\ResourceModel\Db\AbstractDb.php(367): Magento\Framework\DB\Select->where('`store`.`store_...', '1')
#9 \vendor\magento\module-store\Model\ResourceModel\Store.php(168): Magento\Framework\Model\ResourceModel\Db\AbstractDb->_getLoadSelect('store_id', '1', Object(Magento\Store\Model\Store\Interceptor))
#10 \vendor\magento\framework\Model\ResourceModel\Db\AbstractDb.php(341): Magento\Store\Model\ResourceModel\Store->_getLoadSelect('store_id', '1', Object(Magento\Store\Model\Store\Interceptor))
#11 \var\generation\Magento\Store\Model\ResourceModel\Store\Interceptor.php(89): Magento\Framework\Model\ResourceModel\Db\AbstractDb->load(Object(Magento\Store\Model\Store\Interceptor), '1', NULL)
#12 \vendor\magento\framework\Model\AbstractModel.php(531): Magento\Store\Model\ResourceModel\Store\Interceptor->load(Object(Magento\Store\Model\Store\Interceptor), '1', NULL)
#13 \vendor\magento\module-store\Model\Store.php(488): Magento\Framework\Model\AbstractModel->load('1', NULL)
#14 \var\generation\Magento\Store\Model\Store\Interceptor.php(24): Magento\Store\Model\Store->load('1', NULL)
#15 \vendor\magento\module-store\Model\StoreRepository.php(89): Magento\Store\Model\Store\Interceptor->load('1')
#16 \vendor\magento\module-store\Model\StoreRepository.php(103): Magento\Store\Model\StoreRepository->getById('1')
#17 \vendor\magento\module-store\Model\StoreResolver.php(167): Magento\Store\Model\StoreRepository->getActiveStoreById('1')
#18 \vendor\magento\module-store\Model\StoreResolver.php(105): Magento\Store\Model\StoreResolver->getDefaultStoreById('1')
#19 \vendor\magento\module-store\Model\StoreManager.php(151): Magento\Store\Model\StoreResolver->getCurrentStoreId()
#20 \vendor\magento\module-store\App\Request\PathInfoProcessor.php(39): Magento\Store\Model\StoreManager->getStore('')
#21 \vendor\magento\module-backend\App\Request\PathInfoProcessor.php(47): Magento\Store\App\Request\PathInfoProcessor->process(Object(Magento\Framework\App\Request\Http), '/')
#22 \var\generation\Magento\Backend\App\Request\PathInfoProcessor\Proxy.php(95): Magento\Backend\App\Request\PathInfoProcessor->process(Object(Magento\Framework\App\Request\Http), '/')
#23 \vendor\magento\framework\App\Request\Http.php(165): Magento\Backend\App\Request\PathInfoProcessor\Proxy->process(Object(Magento\Framework\App\Request\Http), '/')
#24 \vendor\magento\framework\HTTP\PhpEnvironment\Request.php(209): Magento\Framework\App\Request\Http->setPathInfo()
#25 \vendor\magento\framework\App\Request\Http.php(208): Magento\Framework\HTTP\PhpEnvironment\Request->getPathInfo()
#26 \vendor\magento\framework\App\Http.php(130): Magento\Framework\App\Request\Http->getFrontName()
#27 \vendor\magento\framework\App\Bootstrap.php(258): Magento\Framework\App\Http->launch()
#28 \index.php(39): Magento\Framework\App\Bootstrap->run(Object(Magento\Framework\App\Http))
#29 {main}";s:3:"url";s:6:"/ce21/";s:11:"script_name";s:15:"/ce21/index.php";}

Cache issue

a:5:{i:0;s:71:"Could not determine temp directory, please specify a cache_dir manually";i:1;s:4546:"#0 /home/host/domains/example.com/public_html/lib/Zend/Cache/Backend.php(197): Zend_Cache::throwException('Could not deter...')

Session issue

Warning: SessionHandler::read(): open(/var/lib/php/session/sess_cvevqn06desuj80, O_RDWR) failed: Permission denied (13) in /var/www/vhosts/[site]/httpdocs/vendor/magento/framework/Session/SaveHandler.php on line 74

Registry issue

a:5:{i:0;s:63:"Mage registry key "_singleton/megamenu/observer" already exists";i:1;s:2654:"#0 /home/host/public_html/magento2/app/Mage.php(223): Mage::throwException('Mage registry k...')
#1 /home/host/public_html/magento2/app/Mage.php(477): Mage::register('_singleton/mega...', false)
#2 /home/host/public_html/magento2/app/code/core/Mage/Core/Model/App.php(1335): Mage::getSingleton('megamenu/observ...')
#3 /home/host/public_html/magento2/app/Mage.php(448): Mage_Core_Model_App->dispatchEvent('core_layout_blo...', Array)
#4 /home/host/public_html/magento2/app/code/core/Mage/Core/Model/Layout.php(459): Mage::dispatchEvent('core_layout_blo...', Array)
#5 /home/host/public_html/magento2/app/code/core/Mage/Core/Model/Layout.php(472): Mage_Core_Model_Layout->createBlock('page/html', 'root')
#6 /home/host/public_html/magento2/app/code/core/Mage/Core/Model/Layout.php(239): Mage_Core_Model_Layout->addBlock('page/html', 'root')
#7 /home/host/public_html/magento2/app/code/core/Mage/Core/Model/Layout.php(205): Mage_Core_Model_Layout->_generateBlock(Object(Mage_Core_Model_Layout_Element), Object(Mage_Core_Model_Layout_Element))
#8 /home/host/public_html/magento2/app/code/core/Mage/Core/Controller/Varien/Action.php(344): Mage_Core_Model_Layout->generateBlocks()
#9 /home/host/public_html/magento2/app/code/core/Mage/Cms/Helper/Page.php(113): Mage_Core_Controller_Varien_Action->generateLayoutBlocks()
#10 /home/host/public_html/magento2/app/code/core/Mage/Cms/Helper/Page.php(52): Mage_Cms_Helper_Page->_renderPage(Object(Mage_Cms_IndexController), 'home')
#11 /home/host/public_html/magento2/app/code/core/Mage/Cms/controllers/IndexController.php(45): Mage_Cms_Helper_Page->renderPage(Object(Mage_Cms_IndexController), 'home')
#12 /home/host/public_html/magento2/app/code/core/Mage/Core/Controller/Varien/Action.php(418): Mage_Cms_IndexController->indexAction()
#13 /home/host/public_html/magento2/app/code/core/Mage/Core/Controller/Varien/Router/Standard.php(254): Mage_Core_Controller_Varien_Action->dispatch('index')
#14 /home/host/public_html/magento2/app/code/core/Mage/Core/Controller/Varien/Front.php(172): Mage_Core_Controller_Varien_Router_Standard->match(Object(Mage_Core_Controller_Request_Http))
#15 /home/host/public_html/magento2/app/code/core/Mage/Core/Model/App.php(365): Mage_Core_Controller_Varien_Front->dispatch()
#16 /home/host/public_html/magento2/app/Mage.php(684): Mage_Core_Model_App->run(Array)
#17 /home/host/public_html/magento2/index.php(84): Mage::run('', 'store')
#18 {main}";s:3:"url";s:19:"/magento2/";s:11:"script_name";s:28:"/magento2/index.php";s:4:"skin";s:7:"default";}