Download the Default software to your Host Machine from https://developer.nvidia.com/linux-tegra-rel-19
Extract the contents of the file using tar xvpf Tegra124_Linux_R19.3.0_armhf.tbz2 the use of xvpf preserves any permissions in the file as is.
Download the example root file system from https://developer.nvidia.com/sites/default/files/akamai/mobile/files/L4T/Tegra_Linux_Sample-Root-Filesystem_R19.3.0_armhf.tbz2
Move into Linux_For_Tegra => rootfs and call 'tar xvpf /Tegra_Linux_Sample-Root-Filesystem_R19.3.0_armhf.tbz2 and extract the contents into rootfs
Attach the Jetson board via the USB to USB-Micro-B cable
Boot the Jetson into recovery mode by holding down "Force recovery" and pressing reset, hold down "force recovery" for 2-5 seconds.
On the Host machine, move into the Linux_for_Tegra folder and run the apply_binaries.sh
On the host machine, run sudo ./flash.sh -S 14500MiB jetson-tk1 mmcblk0p1 -S specifies the size of the disk to create on the board, Default is 8000MiB, 15000MiB is larger than available
If this Fails saying that the loop failed you may need to Edit the flash.sh to use the absolute path of losetup. First ensure that losetup is installed. try 'sudo losetup --find' this should give you a result of /dev/loop0
If this does not work try 'sudo /sbin/losetup --find'
Still no joy? try 'sudo /sbin/modprobe losetup' and then running 'sudo /sbin/losetup --find' again
If this still gives you no feedback or feedback that is not positive, update, and add losetup to your $PATH with 'export PATH=$PATH:' Then reboot and try the above flash call again.