how to clear centos cache code example

Example 1: linux memory cache clear

# clear pagecache only.
sync; echo 1 > /proc/sys/vm/drop_caches

# clear dentries and inodes.
sync; echo 2 > /proc/sys/vm/drop_caches

# clear pagecache, dentries and inodes.
sync; echo 3 > /proc/sys/vm/drop_caches

Example 2: clear cache yum centos 7

#To clean all cached packages from the enabled repository cache directory
yum clean packages

#To purge the old package information completely
yum clean headers

#To clean any cached xml metadata from any enabled repository,
yum clean metadata

#To clean all the cached files from any enabled repository at once,
yum clean all

#change yum file settings
nano /etc/yum.conf
http_caching=none

Example 3: how to clear memory in ubuntu 18.04

# Clear PageCache, dentries and inodes.
sync; echo 3 > /proc/sys/vm/drop_caches