How to Clear Cache in Linux

Steps to Clear RAM Memory Cache in Linux

Clearing RAM memory cache on Linux can help improve system performance by freeing up memory used by cached data. Most Linux systems provide three different ways to clear the cache. These methods can be used without affecting running processes or services.

Most Linux systems provide three ways to clear the cache. These methods can be used without affecting running processes or services.

Below are the three different ways:

Clear PageCache Only

The PageCache stores recently used data and files. Clearing it doesn’t affect running processes and is the safest method. To clear only the PageCache, use the following command:

Command:

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

Steps:

• Open the terminal.
• To check memory usage before clearing the cache, type:

free

This command shows memory usage, including swap and available memory. Run this before and after clearing the cache to see changes.

• To clear the PageCache, type:

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

This will clean the PageCache and free up memory used by cached file data.

Clear Dentries and Inodes

Dentries and inodes are used by the system to manage files and directories. Clearing these entries can help when the system’s filesystem holds a large number of files in memory. To clear only dentries and inodes, use:

Command:

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

Steps:

• Open the terminal.
• Type the following command to check memory usage before clearing the cache:

free

To clear dentries and inodes, type:

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

This will remove the cached directory and file metadata from memory.

Clear Dentries, Inodes, and PageCache

This method clears the PageCache, dentries, and inodes, freeing up the most memory. However, it’s not recommended for production environments or frequent use as it can impact system performance.

Command:

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

Steps:

• Open the terminal.
• Type the following command to check memory usage:

free

• To clear all caches, type:

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

This will clear the PageCache, dentries, and inodes, freeing up memory.

Steps to Clear Swap Space Cache in Linux

Clearing the swap space in Linux involves turning off the swap, which moves the data from the swap partition back into RAM. This process can help free up memory and potentially improve system performance, especially when your system has been using swap space heavily.

• Turn Off Swap: To clear the swap space, disable the swap partition using the swapoff. This will transfer data from the swap back into RAM.

Command:

Steps:

• Open the terminal by pressing Ctrl + Alt + T.
• Run the following command to disable swap:

sudo swapoff -a 

• To check memory usage, run:
• Turn Swap Back On: After clearing the swap, you can re-enable it by using the swapon command. This will allow the system to start using swap space again.

Command:

sudo swapon -a

Steps:

• To re-enable the swap, type the following command:
• Verify that the swap is back on by running the following:

Adjust Swappiness

Swappiness is a kernel parameter that controls how aggressively the system uses swap space. By default, it is set to 60, meaning the system will begin swapping when memory usage exceeds 60%. Adjusting this value can help you optimize memory usage based on your system’s needs.

Here are the steps to adjust swappiness:

1. View Current Swappiness Value: To check the current swappiness value, run the following command:

cat /proc/sys/vm/swappiness

This will display the current swappiness value, which is typically set to 60 by default.

2. Change Swappiness Value: To change the swappiness value, you can use the sysctl command. The swappiness value can be set anywhere between 0 and 100:

• 0: The system will avoid using swap as much as possible.
• 100: The system will prefer swapping over freeing up pages in memory.

sudo sysctl vm.swappiness=x

Replace x with a value between 0 and 100. For example, to set swappiness to 20:

sudo sysctl vm.swappiness=20

This command will change the swappiness value for the current session.

3. Verify the Change: To ensure the swappiness value has been successfully changed, run:

This will display the new swappiness value.

Conclusion

Clearing cache for RAM, buffer, and swap space in Linux can significantly enhance system performance by freeing up resources. While it’s safe to clear these areas when needed, it may cause a brief slowdown as the system rebuilds the cache.

To streamline the process, automating cache management with cron jobs ensures your system stays efficient without manual intervention. Regularly clearing the cache in Linux helps maintain smooth performance and ensures that your system remains responsive.

sudo swapoff -a

free -m

Adjust Swappiness