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

Question

$ echo 3 > /proc/sys/vm/drop_caches
bash: /proc/sys/vm/drop_caches: Permission denied

Tried with the system password. But still failing.

Answer 1

Execute the shell as root:

sudo sh -c 'echo 3 > /proc/sys/vm/drop_caches'

Or redirect the input to a process that will write to file as root:

echo 3 | sudo tee /proc/sys/vm/drop_caches