Linux Clear Cache

How to Clear Cache in Linux?

  1. Clear PageCache only.

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

  1. Clear dentries and inodes.

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

  1. Clear PageCache, dentries and inodes.

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

sync will flush the file system buffer. Command Separated by “;” run sequentially.

Now we will be creating a shell script to auto clear RAM cache daily at 2am via a cron scheduler task. Create a shell script clearcache.sh and add the following lines.

#!/bin/bash
# Note, we are using "echo 3", but it is not recommended in production instead use "echo 1"
echo "echo 3 > /proc/sys/vm/drop_caches"

Set execute permission on the clearcache.sh file.

# chmod 755 clearcache.sh

Now set a cron to clear RAM cache everyday at 2am. Open crontab for editing.

# crontab -e

Append the below line, save and exit to run it at 2am daily.

0 2 * * * /path/to/clearcache.sh

How to Clear Swap Space in Linux?

# swapoff -a && swapon -a

Now we will be combining both above commands into one single command to make a proper script to clear RAM Cache and Swap Space.

# echo 3 > /proc/sys/vm/drop_caches && swapoff -a && swapon -a && printf '\n%s\n' 'Ram-cache and Swap Cleared'
OR
$ su -c "echo 3 >'/proc/sys/vm/drop_caches' && swapoff -a && swapon -a && printf '\n%s\n' 'Ram-cache and Swap Cleared'" root

Tips

  • dropcache.sh

sudo sh -c 'echo 1 > /proc/sys/vm/drop_caches'
sudo sh -c 'echo 2 > /proc/sys/vm/drop_caches'
sudo sh -c 'echo 3 > /proc/sys/vm/drop_caches'

References