# adb devices
List of devices attached
0909da6e recovery
# adb reboot bootloader
# sudo fastboot devices
0909da6e fastboot
# sudo fastboot oem unlock
(bootloader) Unlocking bootloader...
(bootloader) erasing userdata...
(bootloader) erasing userdata done
(bootloader) erasing cache...
(bootloader) erasing cache done
(bootloader) Unlocking bootloader done!
OKAY [ 24.086s]
Finished. Total time: 24.086s
# sudo fastboot flash recovery twrp-3.5.2_9-0-flo.img
Sending 'recovery' (10060 KB) OKAY [ 0.325s]
Writing 'recovery' OKAY [ 0.386s]
Finished. Total time: 0.723s
# sudo fastboot reboot recovery