Originally Posted by ErickST18
My question is: Is it possible to enable usb debugging mode using adb or fastboot commands?
No, it is not possible. This would be a massive security issue, as it would defeat the entire purpose of having that setting in the phone, since it would allow full access to your phone without logging into the OS.
Pro-tip: You should really leave that setting turned off until you actually need it, because otherwise anyone can plug in a USB cable and get full access to send fastboot commands to your device (including bypassing lock screens).
Atrix HD (AT&T) - KitKat 4.4.4, CM11 20140914-NIGHTLY-moto_msm8960_jbbl