I am running Virtualbox. I increased the size of my hard disk (.vdi) from 10G to 15G. Now when I start my Mint vm, the hard disk reports as 7.5g (df) even though i extended it (fdisk -l). I am not sure what is the problem. Can anyone point me the problem?

```
$ df -h
Filesystem      Size  Used Avail Use% Mounted on
/dev/sda1     >>7.5G<< 7.1G   61M 100% /
udev            1.5G  4.0K  1.5G   1% /dev
tmpfs           581M  888K  581M   1% /run
none            5.0M     0  5.0M   0% /run/lock
none            1.5G   88K  1.5G   1% /run/shm

$ sudo fdisk -l
Disk /dev/sda: >>16.1 GB<<, 16106127360 bytes
255 heads, 63 sectors/track, 1958 cylinders, total 31457280 sectors
Units = sectors of 1 * 512 = 512 bytes
Sector size (logical/physical): 512 bytes / 512 bytes
I/O size (minimum/optimal): 512 bytes / 512 bytes
Disk identifier: 0x000c55a4

   Device Boot      Start         End      Blocks   Id  System
/dev/sda1   *        2048    15728639     7863296   83  Linux
/dev/sda2        15730686    16775167      522241    5  Extended
/dev/sda5        15730688    16775167      522240   82  Linux swap / Solaris

$ vboxmanage showhdinfo mint.vdi
UUID:                 a94931b9-673c-440a-ab6b-2c3eedd0cf93
Accessible:           yes
Logical size:         15360 MBytes
Current size on disk: 7806 MBytes
Type:                 normal (base)
Storage format:       VDI
Format variant:       dynamic default
Location:             /opt/virtualization/vm/mint.vdi

```