cmd = "/sbin/swapoff -v /dev/vdb1";// /sbin/swapoff -v /dev/xvda1
cmd = "dd if=/dev/zero of=/home/swap bs=1024 count=4096000";//增加swap
cmd = "/sbin/mkswap /home/swap";
cmd = "/sbin/swapon /home/swap";
cmd = "sed -i '$d' /etc/fstab";
cmd = "echo '/home/swap swap swap defaults 0 0' >> /etc/fstab";