On some devices (OnePlus, older Xiaomi, Motorola), the bootloader interface is exposed via the fastboot command even within Android if you have the right binaries.
Relocking requires wiping all user data for security reasons. Back up everything before you start. how to relock bootloader without pc
Thus, without a PC, you’re asking the bootloader to lock itself. That’s like asking a lock to close without a key. Possible only if the manufacturer left a backdoor (recovery menu option). On some devices (OnePlus, older Xiaomi, Motorola), the
Before diving into methods, understand these critical points: On some devices (OnePlus
echo "locked" > /sys/devices/platform/msm_hsic_host/power/control