[root@liutao ~]# swapon -a   #开启swap
swapon: /swap: insecure permissions 0644, 0600 suggested.
[root@liutao ~]# free -m
              total        used        free      shared  buff/cache   available
Mem:           1838         550         831           0         456        1124
Swap:          1023           0        1023
[root@liutao ~]# swapoff -a   #关闭swap
[root@liutao ~]# free -m
              total        used        free      shared  buff/cache   available
Mem:           1838         549         832           0         456        1124
Swap:             0           0           0