Where is the space available on my SD?

[D1eguete]

Hi.

I´m a new user of Xbian.

I have a problem with the available space on my SD.
Only 400 Mb free of 8 Gb.

only xbian with some widgets and skins and sickrage. ¿this is normal occuped space?

I executed three commands:

du -h / | grep ^[0-9].K >filesKb.txt
du -h / | grep ^[0-9].M >filesMb.txt
du -h / | grep ^[0-9].G >filesGb.txt

the addition of sizes of every line in three files is much lower than 4 Gb, but when I do a
df -h / the result is:

Filesystem Size Used Avail Use% Mounted on
/dev/mmcblk0p2 7.2G 6.5G 424M 94% /

Where are the other 3Gb ? How can I see where is my lost space?

thanks in advance.