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.