Ran into an issue today with ESXi 4.1 hosts that I forgot the root password for. The hosts were operating fine in the vSphere 4.1 cluster. However, I need to upgrade the hosts and may need to add them back into a new cluster, which would require the root password. I Googled "reset esxi root password" and came up with this VMware KB article:
http://kb.vmware.com/selfservice/microsites/search.do?language=en_US&cmd=displayKC&externalId=1317898
This line was discouraging: Reinstalling the ESXi host is the only supported way to reset a password on ESXi.
Not one to give up, I remembered that ESXi hosts can be configured through vCenter to use Active Directory for host login:
http://blogs.vmware.com/vsphere/2012/09/joining-vsphere-hosts-to-active-directory.html
I successfully joined the three ESXi 4.1 hosts to AD, created an ESX Admins AD group, and added my AD account to the ESX Admins group. I then was able to connect directly to each host with the vSphere Client using my AD account. Once connected to the hosts, I clicked on the Users and Group tab, clicked on the root account and changed the password.
Crisis avoided.
Labels: root password esxi reset vsphere