I'm using the following commands to flush cache:

# sync; echo 3 > /proc/sys/vm/drop_caches
# sync; echo 2 > /proc/sys/vm/drop_caches
# sync; echo 1 > /proc/sys/vm/drop_caches

When I use one of the above commands, I get the following:

-bash: /proc/sys/vm/drop_caches: Permission denied

My system running CentOS 6.5, I logged in as root via SSH.

Any suggestions?

  • Check what you're typing? It appears as though you've used a ';' where a '>' should be and are trying to execute `/proc/sys/vm/drop_caches'. – Matthew Ife Dec 28 '13 at 13:32
  • Two questions: why do you need to drop your cache? Second, why are you signing in via ssh as root? – EEAA Dec 28 '13 at 13:36
  • 1
    Third question: is this a OpenVZ VPS? – EEAA Dec 28 '13 at 13:44
  • Yes it is OpenVZ. My VPS always running out of memory and goes down. I have 1024 MB memory, hosting 4 websites. They are all inactive and don't have any visits, but when I decide to open WHMCS back-end in one of the websites, the VPS goes down after couple of minutes. Rest other websites are static pages only. That's why I need to find a way to free up some memory. @EEAA – Mina Hafzalla Dec 28 '13 at 15:21
  • This would not solve the problem, even if you could do it. It would only make matters even worse. – Michael Hampton Aug 6 '14 at 4:04

Your CentOS is most likely running as an OpenVZ container and as such you don't have access to the host's /proc/sys/vm/drop_caches.

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