linux的df命令用来查看磁盘情况的，很简单，但工作中很常用。/dev/sda1大小总是在不断变化，也要防止其爆满。
virtual-machine:/mnt/hgfs/vmShare$ df -h
文件系统 容量 已用 可用 已用% 挂载点
udev 943M 0 943M 0% /dev
tmpfs 195M 3.2M 192M 2% /run
/dev/sda1 20G 18G 1.5G 92% /
tmpfs 974M 0 974M 0% /dev/shm
tmpfs 5.0M 4.0K 5.0M 1% /run/lock
tmpfs 974M 0 974M 0% /sys/fs/cgroup
/dev/loop0 3.8M 3.8M 0 100% /snap/gnome-system-monitor/127
/dev/loop1 45M 45M 0 100% /snap/gtk-common-themes/1353
/dev/loop2 157M 157M 0 100% /snap/gnome-3-28-1804/110
/dev/loop3 141M 141M 0 100% /snap/gnome-3-26-1604/97
/dev/loop4 157M 157M 0 100% /snap/gnome-3-28-1804/91
/dev/loop5 1.0M 1.0M 0 100% /snap/gnome-logs/73
/dev/loop6 1.0M 1.0M 0 100% /snap/gnome-logs/81
/dev/loop7 4.3M 4.3M 0 100% /snap/gnome-calculator/536
/dev/loop8 15M 15M 0 100% /snap/gnome-characters/399
/dev/loop12 15M 15M 0 100% /snap/gnome-characters/375
/dev/loop13 4.3M 4.3M 0 100% /snap/gnome-calculator/544
/dev/loop14 55M 55M 0 100% /snap/core18/1650
/dev/loop9 45M 45M 0 100% /snap/gtk-common-themes/1440
/dev/loop11 141M 141M 0 100% /snap/gnome-3-26-1604/98
/dev/loop16 3.8M 3.8M 0 100% /snap/gnome-system-monitor/123
/dev/loop15 90M 90M 0 100% /snap/core/8268
/dev/loop10 55M 55M 0 100% /snap/core18/1279
/dev/loop17 90M 90M 0 100% /snap/core/8213
tmpfs 195M 16K 195M 1% /run/user/121
vmhgfs-fuse 178G 35G 143G 20% /mnt/hgfs
tmpfs 195M 40K 195M 1% /run/user/1000
/dev/sr0 1.9G 1.9G 0 100% /media/mapan/Ubuntu 18.04.1 LTS amd64
