Currently the pre-installed OS of IGT-20 is Debian 8, and the OS image is less than 1GB in a 8GB microSD. By using df command, one can observe the real disk usage as below:

root@igt20:~#df
Filesystem     1K-blocks   Used Available Use% Mounted on
udev               10240      0     10240   0% /dev
tmpfs             203848   5332    198516   3% /run
/dev/mmcblk1p0    836280 417880    358704  54% /
tmpfs             509616      0    509616   0% /dev/shm
tmpfs               5120      0      5120   0% /run/lock
tmpfs             509616      0    509616   0% /sys/fs/cgroup

The image occupies around 850MB while 54% is still not used. With another command cfdisk, one can find the total microSD capacity and the free space

As shown in the picture, the real capacity is 7.5GB (8,010,072,064 bytes) with 6.6GB not located. Since IGT-20 provides the other external microSD slot, it’s better to store the user data in the external microSD. However, in some cases, if you’d not like to have another SD, it’s better to create a new partition using the 6.6G free space instead of extending the original partition.