cd <your Magento install dir>

find . -type f -exec chmod 644 {} ;                        // 644 permission for files

find . -type d -exec chmod 755 {} ;                        // 755 permission for directory

find ./var -type d -exec chmod 777 {} ;                // 777 permission for var folder

find ./pub/media -type d -exec chmod 777 {} ;

find ./pub/static -type d -exec chmod 777 {} ;

chmod 777 ./app/etc

chmod 644 ./app/etc/*.xml

chown -R :<web server group> .

chmod u+x bin/magento

There might be 2 case

php bin/magento setup:upgrade
php bin/magento setup:static-content:deploy
rm -rf var/cache/ var/generation/ var/page_cache/ var/view_preprocessed/
rm -rf pub/static/frontend/ pub/static/adminhtml/ pub/static/_requirejs/

find . -type f -exec chmod 644 {} ;
find . -type d -exec chmod 755 {} ;
find ./var -type d -exec chmod 777 {} ;
find ./pub/media -type d -exec chmod 777 {} ;
find ./pub/static -type d -exec chmod 777 {} ;
chmod 777 ./app/etc
chmod 644 ./app/etc/*.xml