Step 1 – Download and install Raspbian image on the USB Flash and MicroSD
Step 2 – Enable usb boot option
sudo nano /boot/config.txt
Add program_usb_boot_mode=1
Step 3 - Reboot
Step 4 - Edit cmdline.txt
change line
"root=/dev/mmcblk0p2" to "root=/dev/sda2"
Step 5 - Shutdown raspberry pi
Step 6 - Plug usb flash and power on raspberry pi
Still needed sd card
Step 2 – Enable usb boot option
sudo nano /boot/config.txt
Add program_usb_boot_mode=1
Step 3 - Reboot
Step 4 - Edit cmdline.txt
change line
"root=/dev/mmcblk0p2" to "root=/dev/sda2"
Step 5 - Shutdown raspberry pi
Step 6 - Plug usb flash and power on raspberry pi
Still needed sd card