I have a server with 2 magento 2 instances installed. Each one is owned by a different user. One instance works flawlessly, the other has a small issue :
when I try to flush the cache from backend I got the following error ( I encounter no errors when flushing from ssh running php bin/magento cache:clean and php bin/magento cache:flush ) as far as I know folders and files permissions are correct and ownership aswell (m2owner:www-data).
Exception #0 (RuntimeException): The file "/opt/m2/auth.json" is not readable.
<pre>#1 ComposerFactory::validateJsonSchema() called at [vendor/composer/composer/src/Composer/Factory.php:338]
#2 ComposerFactory->createComposer() called at [vendor/composer/composer/src/Composer/Factory.php:629]
#3 ComposerFactory::create() called at [vendor/magento/framework/Composer/ComposerFactory.php:45]
#4 MagentoFrameworkComposerComposerFactory->create() called at [vendor/magento/framework/Composer/ComposerInformation.php:368]
#5 MagentoFrameworkComposerComposerInformation->getComposer() called at [vendor/magento/framework/Composer/ComposerInformation.php:381]
#6 MagentoFrameworkComposerComposerInformation->getLocker() called at [vendor/magento/framework/Composer/ComposerInformation.php:244]
#7 MagentoFrameworkComposerComposerInformation->getSystemPackages() called at [vendor/magento/framework/App/ProductMetadata.php:120]
#8 MagentoFrameworkAppProductMetadata->getSystemPackageVersion() called at [vendor/magento/framework/App/ProductMetadata.php:80]
#9 MagentoFrameworkAppProductMetadata->getVersion() called at [vendor/magento/module-admin-notification/Model/Feed.php:235]
#10 MagentoAdminNotificationModelFeed->getFeedData() called at [vendor/magento/module-admin-notification/Model/Feed.php:164]
#11 MagentoAdminNotificationModelFeed->checkUpdate() called at [vendor/magento/module-admin-notification/Observer/PredispatchAdminActionControllerObserver.php:50]
#12 MagentoAdminNotificationObserverPredispatchAdminActionControllerObserver->execute() called at [vendor/magento/framework/Event/Invoker/InvokerDefault.php:88]
#13 MagentoFrameworkEventInvokerInvokerDefault->_callObserverMethod() called at [vendor/magento/framework/Event/Invoker/InvokerDefault.php:74]
#14 MagentoFrameworkEventInvokerInvokerDefault->dispatch() called at [vendor/magento/framework/Event/Manager.php:65]
#15 MagentoFrameworkEventManager->dispatch() called at [generated/code/Magento/Framework/Event/Manager/Proxy.php:95]
#16 MagentoFrameworkEventManagerProxy->dispatch() called at [vendor/magento/framework/App/FrontController.php:271]
#17 MagentoFrameworkAppFrontController->dispatchPreDispatchEvents() called at [vendor/magento/framework/App/FrontController.php:211]
#18 MagentoFrameworkAppFrontController->processRequest() called at [vendor/magento/framework/App/FrontController.php:146]
#19 MagentoFrameworkAppFrontController->dispatch() called at [vendor/magento/framework/Interception/Interceptor.php:58]
#20 MagentoFrameworkAppFrontControllerInterceptor->___callParent() called at [vendor/magento/framework/Interception/Interceptor.php:138]
#21 MagentoFrameworkAppFrontControllerInterceptor->MagentoFrameworkInterception{closure}() called at [vendor/magento/framework/Interception/Interceptor.php:153]
#22 MagentoFrameworkAppFrontControllerInterceptor->___callPlugins() called at [generated/code/Magento/Framework/App/FrontController/Interceptor.php:23]
#23 MagentoFrameworkAppFrontControllerInterceptor->dispatch() called at [vendor/magento/framework/App/Http.php:116]
#24 MagentoFrameworkAppHttp->launch() called at [generated/code/Magento/Framework/App/Http/Interceptor.php:23]
#25 MagentoFrameworkAppHttpInterceptor->launch() called at [vendor/magento/framework/App/Bootstrap.php:264]
#26 MagentoFrameworkAppBootstrap->run() called at [pub/index.php:30]
</pre>
any idea on how to get this to work from the back-end as it`s supposed to?
