Quote Originally Posted by Wim Sturkenboom View Post
Read up on sparse files

Step 1
Check diskspace before creating a 1GB file
Code:
wim@i3-2120:/mnt$ du --max-depth=1
32	./boot-sav
219602196	./photos
219602232	.
wim@i3-2120:/mnt$ df -h
Filesystem      Size  Used Avail Use% Mounted on
/dev/sda5       138G  4,9G  126G   4% /
udev            3,7G  4,0K  3,7G   1% /dev
tmpfs           1,5G  856K  1,5G   1% /run
none            5,0M     0  5,0M   0% /run/lock
none            3,7G  216K  3,7G   1% /run/shm
/dev/sda6       532G   14G  491G   3% /home
/dev/sdc1       925G  210G  706G  23% /mnt/photos
Step 2
Create a 1GB file
Code:
wim@i3-2120:/mnt$ cd photos/wim/
wim@i3-2120:/mnt/photos/wim$ dd if=/dev/null of=sparse-file bs=1k seek=1000000 count=1
0+0 records in
0+0 records out
0 bytes (0 B) copied, 2,112e-05 s, 0,0 kB/s
wim@i3-2120:/mnt/photos/wim$ ls -l
total 33016
-rwxr-xr-x 1 wim wim    6068196 Jan 11  2011 IMGP2310 (copy).jpg
-rwxr-xr-x 1 wim wim   10801944 Jan 11  2011 IMGP2310 (copy).PEF
-rwxr-xr-x 1 wim wim    6068196 Jan 11  2011 IMGP2310.jpg
-rwxr-xr-x 1 wim wim   10801944 Jan 11  2011 IMGP2310.PEF
-rw-rw-r-- 1 wim wim 1024000000 Nov 30 16:05 sparse-file
Step 3
Check available diskspace after creating 1GB file
Code:
wim@i3-2120:/mnt/photos/wim$ du --max-depth=1 /mnt
32	/mnt/boot-sav
219602196	/mnt/photos
219602232	/mnt
wim@i3-2120:/mnt/photos/wim$ df -h
Filesystem      Size  Used Avail Use% Mounted on
/dev/sda5       138G  4,9G  126G   4% /
udev            3,7G  4,0K  3,7G   1% /dev
tmpfs           1,5G  856K  1,5G   1% /run
none            5,0M     0  5,0M   0% /run/lock
none            3,7G  216K  3,7G   1% /run/shm
/dev/sda6       532G   14G  491G   3% /home
/dev/sdc1       925G  210G  706G  23% /mnt/photos
Note that the disk usage / free space did not change
Of course it didn't change, you created the 1GB file on sdc1 partition, NOT the / partition.