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Just upgraded successfully to Magento 2.1.2 through composer:

composer require magento/product-community-edition 2.1.2 --no-update

Change the version accordingly e.g. 2.1.3

composer update
rm -rf var/di var/generation/* var/view_preprocessed/* var/cache/* var/page_cache
 
chown -R user:group .
chmod u+x bin/magento
php bin/magento cache:flush
php bin/magento setup:upgrade
php bin/magento setup:static-content:deploy
php bin/magento indexer:reindex

If getting permissions error, issue:

chown -R user:group .

command again where user and group correspond to your server user and user group.

Just upgraded successfully to Magento 2.2.6 through composer:

composer require magento/product-community-edition 2.2.6 --no-update

Change the version accordingly e.g. 2.2.6

composer update
rm -rf var/di var/generation/* var/view_preprocessed/* var/cache/* var/page_cache

*// The issue following commands one by one

chown -R user:group .
chmod u+x bin/magento
php bin/magento cache:flush
php bin/magento setup:upgrade
ph bin/magento setup:di:compile
php bin/magento setup:static-content:deploy
php bin/magento indexer:reindex

If getting permissions error, issue:

chown -R user:group .

command again where user and group correspond to your server user and user group.

Just upgraded successfully to Magento 2.1.2 through composer:

composer require magento/product-community-edition 2.1.2 --no-update
composer update
rm -rf var/di var/generation/* var/view_preprocessed/* var/cache/* var/page_cache/*

chown -R user:group .
chmod u+x bin/magento
php bin/magento cache:flush
php bin/magento setup:upgrade
php bin/magento setup:static-content:deploy
php bin/magento indexer:reindex

If getting permissions error, issue:

chown -R user:group .

command again where user and group correspond to your server user and user group.

Just upgraded successfully to Magento 2.1.2 through composer:

composer require magento/product-community-edition 2.1.2 --no-update

Change the version accordingly e.g. 2.1.3

composer update
rm -rf var/di var/generation/* var/view_preprocessed/* var/cache/* var/page_cache

chown -R user:group .
chmod u+x bin/magento
php bin/magento cache:flush
php bin/magento setup:upgrade
php bin/magento setup:static-content:deploy
php bin/magento indexer:reindex

If getting permissions error, issue:

chown -R user:group .

command again where user and group correspond to your server user and user group.

Just upgraded successfully to Magento 2.1.2 through composer:

composer require magento/product-community-edition 2.1.2 --no-update
composer update
rm -rf var/di var/generation var/view_preprocessed var/cache var/page_cache
chown -R user:group .
chmod u+x bin/magento
php bin/magento cache:flush
php bin/magento setup:upgrade
php bin/magento setup:static-content:deploy
php bin/magento indexer:reindex

If getting permissions error, issue:

chown -R user:group .

command again where user and group correspond to your server user and user group.

Just upgraded successfully to Magento 2.1.2 through composer:

composer require magento/product-community-edition 2.1.2 --no-update
composer update
rm -rf var/di var/generation/* var/view_preprocessed/* var/cache/* var/page_cache/*

chown -R user:group .
chmod u+x bin/magento
php bin/magento cache:flush
php bin/magento setup:upgrade
php bin/magento setup:static-content:deploy
php bin/magento indexer:reindex

If getting permissions error, issue:

chown -R user:group .

command again where user and group correspond to your server user and user group.