smd@SMD-T430:~$ sudo fastboot oem unlock
...
(bootloader) The bootloader is already unlocked!
OKAY [  0.003s]
finished. total time: 0.003s
smd@SMD-T430:~$ sudo fastboot oem lock
...
(bootloader) Locking bootloader...
(bootloader) Locking bootloader done!
OKAY [  0.574s]
finished. total time: 0.574s
smd@SMD-T430:~$ 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 [ 10.575s]
finished. total time: 10.575s