For Changing Root Password of ESXi Server using vSphere Client follow steps below:
1.After installation vSphere client log in to Esxi with VMware vSphere client:
2. Click host and then click the Local Users and Groups tab and select root user and right click on it and click edit :
3. check the check box to Change Password. Enter the new password and click OK button.
So you can use new root password for log in.
