//activate developer mode using live usb linux distro

//first open terminal as root from live usb 

//write this :

fdisk -l

//find efi partition this is the partition we mount it in next stepts

sudo mount /dev/<the efi partition>  /mnt

//then write

cd /mnt

//then

find . -name *.cfg -exec sudo sed -i 's,\(cros_legacy\|cros_efi\),\1 cros_debug,g' {} \;

//finally reboot

reboot

​