Clear cache, buffer and swap space in linux

For clearing cache

[root@laptop ~]# free -h
              total        used        free      shared  buff/cache   available
Mem:           1.7G        944M        170M        113M        653M        492M
Swap:          6.5G          0B        6.5G

//653 M Exisit

[root@laptop ~]# sync; echo 1 > /proc/sys/vm/drop_caches

[root@laptop ~]# free -h
              total        used        free      shared  buff/cache   available
Mem:           1.7G        952M        456M        120M        360M        478M
Swap:          6.5G          0B        6.5G

cache has been reduced. only exist buffer

[root@laptop ~]# sync; echo 2 > /proc/sys/vm/drop_caches
[root@laptop ~]# free -h
              total        used        free      shared  buff/cache   available
Mem:           1.7G        946M        491M        121M        331M        499M
Swap:          6.5G          0B        6.5G

[root@laptop ~]# sync; echo 3 > /proc/sys/vm/drop_caches
[root@laptop ~]# free -h
              total        used        free      shared  buff/cache   available
Mem:           1.7G        952M        481M        126M        335M        488M
Swap:          6.5G          0B        6.5G

For clearing the swap simply use to trun off the swap and trun on it again the swap has been cleared

[root@laptop ~]# swapoff -a
[root@laptop ~]# swapon -a

//before clear swap make sure if any program doesn't run

//now make them altogether in single command

[root@laptop ~]# sync; echo 3 > /proc/sys/vm/drop_caches && swapoff -a && swapon -a && printf '\n%s\n' 'cache ,swap, buffer cleared'

cache ,swap, buffer cleared