How to Clear Cache on Linux?

Every Linux System has three options to clear cache without interrupting any processes or services.

1. Clear PageCache only.

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

2. Clear dentries and inodes.

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

3. Clear PageCache, dentries and inodes.

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

Explanation 

sync will flush the file system buffer. Command Separated by ";" run sequentially. The shell wait for each command to terminate before executing the next command in the sequence. As mentioned in kernel documentation, writing to drop_cache will clean cache without killing any application/service, command echo is doing the job of writing to file.

As a root user