How to clear RAM memory Cache in Linux

Linux is a robust system built with memory management like all other systems. However Linux gives you granular control in freeing the cache. You might sometime find yourself in a situation where a software is consuming more RAM than expected and you just want to free the RAM.

A RAM is a type of volatile storage used to store running apps data and instruction sets. Unlike your other types of storage such as hard disk or SSD which are non-volatile a ram is extremely faster however on power loss all data is cleared.

First method - Rebooting

Now the  understanding of what a RAM is this technically means the first way/method to clear your RAM is rebooting your Linux system.

Second Method - Clearing memory yourself

So you run a VPS or a critical infrastructure and a reboot of your system would cause unnecessary down time. In Linux it is possible to manually clear RAM cache.

The command for clearing cache is sync. We usually append ";" in front of the command so that the command run's sequentially. The final part is writing to drop_cache this is necessary so we can clean the cache without killing any running application/service because that would be a nightmare.

NB: If the commands don't run as sudo run them as root user. To do that run "su -"

Clearing page cache

A page cache is a type cache that emanates from I/O operations on the hard disk / SSD. This is a cache from operations such as read(),write() and mmap().

Clearing inodes and dentries

Inodes are data structures that represent a file while dentries data structures that represent file or folder.

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

Clearing page cache, inodes and dentries

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

Conclusion

Whether for your VPS or your PC you can manually clear RAM cache on your Linux system without rebooting.  You can automate the task by writing a shell script and run the shell script periodically using crontabs.

#!/bin/bash
echo "echo 3 > /proc/sys/vm/drop_caches"