centos 7 添加swap

　　

[root@lab01 /]# cd /
[root@lab01 /]# dd if=/dev/zero of=/swapfile bs=1k count=
+ records in
+ records out
 bytes (2.1 GB) copied, 14.1909 s,  MB/s
[root@lab01 /]# free -m
              total        used        free      shared  buff/cache   available
Mem:
Swap:
[root@lab01 /]# mkswap /swapfile
Setting up swapspace version , size =  KiB
no label, UUID=0cc4aeeb-a55d-430e--297f33bde299
[root@lab01 /]# chmod  /swapfile
[root@lab01 /]# swapon /swapfile
[root@lab01 /]# free -m
              total        used        free      shared  buff/cache   available
Mem:
Swap:
[root@lab01 /]# echo "/swapfile swap swap defaults 0 0" >> /etc/fstab
[root@lab01 /]# cat /etc/fstab 

#
# /etc/fstab
# Created by anaconda on Thu Jul  ::
#
# Accessible filesystems, by reference, are maintained under '/dev/disk'
# See man pages fstab(), findfs(), mount() and/or blkid() for more info
#
UUID=1114fe9e---b183-d778e6d97397 /                       ext4    defaults
/swapfile swap swap defaults