df: no file systems processed

[root@DACS op]# df -h
df: no file systems processed

解决办法：

[root@DACS op]# cat /proc/mounts > /etc/mtab
[root@DACS op]# df -h
Filesystem Size Used Avail Use% Mounted on
/dev/sda5 1.6T 159G 1.3T 11% /
none 492K 0 492K 0% /dev
tmpfs 94G 204K 94G 1% /dev/shm