how to drop_caches in OpenVZ centos6 container

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http://serverfault.com – I have tried sudo sh -c 'echo 3 > /proc/sys/vm/drop_caches' sudo echo 3 > /proc/sys/vm/drop_caches echo 3 > /proc/sys/vm/drop_caches echo 3 | sudo tee /proc/sys/vm/drop_caches and a bunch of other variations but with every try I get bash: /proc/sys/vm/drop_caches: Permission denied How do I clear the ram used for buffers/cache in my centos6 openvz container? It seems like the only way to do what I need is to reboot the container. (HowTos)