SWAP File创建：

# dd if=/dev/zero of=/root/extraswap bs=1M count=512

# ls -l /root/extraswap

# chmod 600 /root/extraswap

# mkswap /root/extraswap

#swapon /root/extraswap

# swapon -s

SWAP File删除

# swapoff /root/extraswap
#  rm /root/extraswap

开机启动加载swap，进到etc/fastab增加一行

 /root/extraswap swap swap defaults 0 0