Clear Cache for lunix

we can use The free command is used to display amount of free and used memory in the system. The command also displays the total amount of swap memory in the system and buffers and caches used by the Linux kernel.

free -m

and to Clear memory we can use :
To clear pagecache only:

sync; echo 1 > /proc/sys/vm/drop_caches

To clear dentries and inodes:

sync; echo 2 > /proc/sys/vm/drop_caches

To clear pagecache, dentries and inodes:

sync; echo 3 > /proc/sys/vm/drop_caches

to empty buffer and cache:

free && sync && echo 3 > /proc/sys/vm/drop_caches && free

if you has this probleme of permission
bash: /proc/sys/vm/drop_caches: Permission denied


you can use echo piped to sudo tee to allow the proper permission needed when you need to echo as root

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