df -h可以把内存大小单位换算为G，让信息更可读一些。-h代表human - 人类可读。
$ df -h
Filesystem Size Used Avail Use% Mounted on
/dev/mapper/centos-root 50G 22G 29G 44% /
devtmpfs 32G 0 32G 0% /dev
tmpfs 32G 75M 32G 1% /dev/shm
tmpfs 32G 259M 32G 1% /run
tmpfs 32G 0 32G 0% /sys/fs/cgroup
/dev/sda3 716G 392G 287G 58% /data0
/dev/sdb1 11T 9.2T 1.1T 90% /data1
/dev/sda5 497M 314M 183M 64% /boot
/dev/mapper/centos-home 39G 38G 1.5G 97% /home
tmpfs 6.3G 12K 6.3G 1% /run/user/42
tmpfs 6.3G 16K 6.3G 1% /run/user/1014
tmpfs 6.3G 0 6.3G 0% /run/user/1001
tmpfs 6.3G 0 6.3G 0% /run/user/1015参考：
https://www.jianshu.com/p/bb263c8d0f07
