hi, thanks for the information. I follow the steps to update cloud-init RPM package to epel-release's 18.3, every things are working well expect change root password. After checking cloud-init.log, I found CentOS6 always locked root password(by inserting "!!" into the /etc/shadow) when first boot, and I have to run command "passwd -u root" to unlock it manually, and then change root password is working. I have tried many ways but not success to disable this first boot locking action. any one know how to disable it ? Thanks.