The SD card is mounted to the path
In the startup script
rcS, you should find the following that mounts the SD card (if it can be found)
# Try to mount the microSD card.
# REBOOTWORK this needs to start after the flight control loop
if mount -t vfat /dev/mmcsd0 /fs/microsd
echo "[i] microSD mounted: /fs/microsd"
if hardfault_log check
if hardfault_log commit
# Start playing the startup tune
If the SD card was mounted correctly, it will appear in the path
/fs/microsd/. If you
cd to this directory and run
ls, you should see the contents of the SD card displayed.
If I am not mistaken you are only able to run
mkdir on a path on your SD card, or on a path where there is a virtual file system that allows writing. The files that you see in
/etc/ are stored directly in the STM32F4 flash, and are "read-only".
I hope that makes some sense to you?