[Debian] Grub - Change Default OS

[user@debian]:~$ cd /etc/default
[user@debian]:/etc/default$ su
Password:
[root@debian:/etc/default# vim grub

#{press "i" and edit file}

# You can select default os, write only numbers, 0 means that linux is
default os
GRUB_DEFAULT=0

# You can change time in seconds
GRUB_TIMEOUT=5

#{press ESC and write ":x"}

After:
[root@debian:/etc/default# update-grub