How to clear RAM Memory Cache, Buffer & Swap Space on Linux
Clearing RAM Memory Cache, Buffer and Swap Space on Linux
Memory management like Clear RAM Memory Cache, Buffer and Swap Space in Linux will be discussed in this article.
To Clear Cache in Linux
Generally all the Linux System will have three options to clear cache without interrupting any services or processes.
To Clear PageCache only
[root@linuxhelp ~]# free -h
total used free shared buffers cached
Mem: 987M 923M 64M 5.1M 0B 240M
-/+ buffers/cache: 682M 304M
Swap: 2.0G 15M 1.9G
[root@linuxhelp ~]# sync echo 1 > /proc/sys/vm/drop_caches
[root@linuxhelp ~]# free -h
total used free shared buffers cached
Mem: 987M 583M 403M 5.1M 0B 38M
-/+ buffers/cache: 544M 442M
Swap: 2.0G 15M 1.9G
To Clear dentries and inodes
[root@linuxhelp ~]# free -h
total used free shared buffers cached
Mem: 987M 585M 401M 5.1M 0B 40M
-/+ buffers/cache: 545M 442M
Swap: 2.0G 15M 1.9G
[root@linuxhelp ~]# sync echo 2 > /proc/sys/vm/drop_caches
[root@linuxhelp ~]# free -h
total used free shared buffers cached
Mem: 987M 576M 410M 5.1M 0B 42M
-/+ buffers/cache: 533M 453M
Swap: 2.0G 15M 1.9G
To Clear PageCache, dentries and inodes
[root@linuxhelp ~]# free -h
total used free shared buffers cached
Mem: 987M 584M 402M 5.1M 0B 50M
-/+ buffers/cache: 533M 453M
Swap: 2.0G 15M 1.9G
[root@linuxhelp ~]# sync echo 3 > /proc/sys/vm/drop_caches
[root@linuxhelp ~]# free -h
total used free shared buffers cached
Mem: 987M 572M 414M 5.1M 0B 38M
-/+ buffers/cache: 534M 453M
Swap: 2.0G 15M 1.9G
sync command will flush the file system buffer. To drop_cache will clean cache without killing any application, echo command is doing the job of writing to file.
" ...echo 1 > &hellip ." will clear the PageCache only. It is not recommended to use third option above
" ...echo 3 > " can clear PageCache, dentries and inodes.
Using Linux Kernel, to free Buffer and Cache in Linux. Create a shell script to auto clear RAM cache daily, through a cron scheduler task. To Create a shell script script.sh by adding the below lines.
[root@linuxhelp ~]# vim script.sh
echo " echo 3 > /proc/sys/vm/drop_caches"
To set run permission on the script.sh file
[root@linuxhelp ~]# chmod 755 script.sh
To clear ram cache, you may call the script whenever required.
Setting a cron to clear RAM cache everyday 2 hours.
[root@linuxhelp ~]# crontab -e
Append the following line, save and exit to execute it at 2 hours daily.
0 2 * * * /path/to/script.sh
To clear automatically the RAM cache on production server
On the scheduled time, the script executes and clear everything in cache. Now all users are fetching data from disk. It will result in server crash and corrupt the database.
To Clear Swap Space in Linux
If you need to clear Swap space, run the following command.
[root@linuxhelp ~]# free -h
total used free shared buffers cached
Mem: 987M 602M 384M 5.1M 0B 71M
-/+ buffers/cache: 531M 455M
Swap: 2.0G 15M 1.9G
[root@linuxhelp ~]# swapoff -a
[root@linuxhelp ~]# swapon -a
[root@linuxhelp ~]# free -h
total used free shared buffers cached
Mem: 987M 615M 371M 8.1M 12K 72M
-/+ buffers/cache: 543M 443M
Swap: 2.0G 0B 2.0G
Add the above command to a cron script, after understanding all the risk. Here we will combine both the commands into one single command, to form a proper script to clear Swap Space and RAM Cache.
[root@linuxhelp ~]# echo 3 > /proc/sys/vm/drop_caches & & swapoff -a & & swapon -a & & printf '
%s
' ' Ram-cache and the swap get cleared'
Now the Ram-cache and the swap gets cleared.
$ su -c " echo 3 > ' /proc/sys/vm/drop_caches' & & swapoff -a & & swapon -a & & printf ' %s ' ' Ram-cache and the swap get cleared’ root
After testing above commands, we will execute " free -h" command before and after executing the script and then we will check the cache.
[root@linuxhelp ~]# free -h
total used free shared buffers cached
Mem: 987M 588M 399M 8.1M 1.4M 43M
-/+ buffers/cache: 543M 444M
Swap: 2.0G 0B 2.0G
sync echo 1 > /proc/sys/vm/drop_caches
dmidecode --type 17
free -h