yay

root@raspberrypi:~# resize2fs /dev/mmcblk0p2
resize2fs 1.42.5 (29-Jul-2012)
Filesystem at /dev/mmcblk0p2 is mounted on /; on-line resizing required
old_desc_blocks = 1, new_desc_blocks = 1
Performing an on-line resize of /dev/mmcblk0p2 to 3629952 (4k) blocks.
The filesystem on /dev/mmcblk0p2 is now 3629952 blocks long.

root@raspberrypi:~# df -h
Filesystem      Size  Used Avail Use% Mounted on
rootfs           14G  1.4G   12G  11% /
/dev/root        14G  1.4G   12G  11% /
tmpfs            19M  212K   19M   2% /run
tmpfs           5.0M     0  5.0M   0% /run/lock
tmpfs            37M     0   37M   0% /tmp
tmpfs            10M     0   10M   0% /dev
tmpfs            37M     0   37M   0% /run/shm
/dev/mmcblk0p1   56M   34M   23M  61% /boot