Symfony 3.4 - how to fix cache.WARNING Failed to save key?

Question

symfony

Hello everyone,
how can I fix these warnings in the log?
cache.Warning: Failed to save key "%5BF...." (DOCTRINE\ORM\Query\ParserResult) Many thanks
in advance

Answer 1

This is the permission of the folder. On Ubuntu in the project folder:
sudo chmod 700 -R var /