df command does not show the root device

Issue

• df command does not show usage of root file system :

[root@host ~]# df
Filesystem           1K-blocks      Used Available Use% Mounted on
/dev/vda1               101086     12848     83019  14% /boot
tmpfs                   125808         0    125808   0% /dev/shm

• However, forcing df to show the usage of / works, but note that it can not find the block device:

[root@host ~]# df /
Filesystem           1K-blocks      Used Available Use% Mounted on
-                      5586528   1445364   3852808  28% /

• The mount -l command does not show the root file system as mounted.