Expanding (resize) persistent & mounted Centos 7 disk size in Custom Google Compute Image.

centos_rootfs_resize.sh

sudo yum install -y cloud-utils-growpart
# You can use lsblk command to check the total available space of you disk.
# growpart is used to to expand a partition to the whole disk (expand sda1 to sda)
# xfs_growfs is used to resize and apply the changes
# df -h
# For more informations : https://blog.myduniahosting.com/how-to-resize-your-root-diskpartition-online-for-linux/

part=`df --output=source / |grep "/dev/"`
if [ ! -z "$part" ] ; then
  len=${#part}
  p=`echo $part|cut -c$len`
  d=`echo $part|cut -c1-$(($len-1))`

  growpart "$d" "$p"
  xfs_growfs "$part"
fi

It worked, thanks!