ubuntu df: cannot read table of mounted file systems: No such file or directory

root@eccubuntu:~# df -lh

df: cannot read table of mounted file systems: No such file or directory

root@eccubuntu:~# grep -v rootfs /proc/mounts > /etc/mtab

root@eccubuntu:~# df -lh

Filesystem            Size  Used Avail Use% Mounted on

none                  7.9G  184K  7.9G   1% /dev

/dev/mapper/eccubuntu-root

                      129G  100G   23G  82% /

none                  7.9G     0  7.9G   0% /dev/shm

none                  7.9G   64K  7.9G   1% /var/run

none                  7.9G     0  7.9G   0% /var/lock

none                  7.9G     0  7.9G   0% /lib/init/rw

/dev/sda1             228M  113M  103M  53% /boot

root@eccubuntu:~#