grub-mkpasswd-pbkdf2
40_custom
--------------
set superusers=“xyzadmin"
password_pbkdf2 xyzadmin grub.pbkdf2.sha512.10000.1378C004EEDDCD0C7DF021170A1BDF00A1BBD4509BBF27DF54047AEBF77F5EA25C424A4EED7E5C068614644B28FC05B533CEC934815B3B8229B88E4697BE2BF3.3210644AE7639B2688862816F3F121480B86CF35839D91FC590BA37BEF9394915EEB8CCE7D13588D44B2BA7AB144DFB4012F8B256AB25EB2
10_linux
--------------
CLASS="--class gnu-linux --class gnu --class os --unrestricted"
update-grub