GRUB_TIMEOUT set to 0

scripts/cleanup.sh

 #!/bin/bash -x
 
+# set GRUB_TIMEOUT to 0
+sudo sed -i "s/^GRUB_TIMEOUT=[0-9]*/GRUB_TIMEOUT=0/" /etc/default/grub
+sudo update-grub
+
 # disable ssh root login using password
 sed -i 's/#\?PermitRootLogin.*/PermitRootLogin without-password/g' /etc/ssh/sshd_config