"echo 3 > /proc/sys/vm/drop_caches" - Permission denied as root

I am currently having some issues with the cache. It is a little too much right now so I wanted to clear it. I googled and found this little command: sync && echo 3 > /proc/sys/vm/drop_caches. I am logged in as root over SSH (not using sudo). These are the attempts I made: root@server: ~ # ll /proc/sys/vm/drop_caches -rw-r--r-- 1 root root 0 15. Jan 20:21 /proc/sys/vm/drop_caches root@server: ~ # echo 3 > /proc/sys/vm/drop_caches -bash: /proc/sys/vm/drop_caches: Permission denied root@server: ~ # sudo su -c "echo 3 > /proc/sys/vm/drop_caches" bash: /proc/sys/vm/drop_caches: Permission denied root@server: ~ # echo 3 | sudo tee /proc/sys/vm/drop_caches tee: /proc/sys/vm/drop_caches: Permission denied 3 It is a remote machine running Debian. As far as I know there are some vCores in this machine and it uses Virtuozzo for the virtualization. I really just want to clear the cache *(So I can only access it using SSH)*. I also tried registering this as a cronjob. But it simply fails too!