When files and system utilities are used by a Linux system, they’re temporarily stored in random access memory (RAM), which makes them much quicker to access. This is a good thing, since frequently accessed information can be quickly recalled, which ultimately makes your system perform faster.
To clear PageCache only, use this command:
$ sudo sysctl vm.drop_caches=1
To clear dentries and inodes, use this command:
$ sudo sysctl vm.drop_caches=2
To clear PageCache, plus dentries and inodes, use this command:
$ sudo sysctl vm.drop_caches=3
You can now use the
free command or
top to check your system’s RAM usage and verify that the cache has been cleared.
If you are running a system that doesn’t use systemd, you can use the following commands to accomplish the same thing as the respective systemctl commands:
$ sync; echo 1 > /proc/sys/vm/drop_caches # clear PageCache $ sync; echo 2 > /proc/sys/vm/drop_caches # clear dentries and inodes $ sync; echo 3 > /proc/sys/vm/drop_caches # clear all 3
Clearing the cache is a simple task but one that only needs to be done in rare situations, such as with development or troubleshooting.