Have you ever been at work or at home working on a computer, entered a command (or otherwise take a critical action) – and as your finger is releasing pressure off of the <enter> key, or the mouse button you suddenly enter a cold sweat, realize what you’ve just done – and suddenly have a horrendous urge to reach for a garbage can to vomit?

I just had one of those moments.  I rebuilt my ESX server, upgrading it from 3.5 to ESXi 4.0 U1.  That went smooth, I presented my iSCSI LUNS – all smooth.

I than upgraded the virtual hardware on my domain controller.  Then I realized that it’s Server 2008 Enterprise edition, then I recalled that I have AD installed on the D: drive, and finally I remembered this KB article.  Essentially, ESX 4 presents VMDKs to systems as a SAN device, which by default Enterprise edition set Offline, until instructed otherwise.

Welcome to a BSOD loop on my only domain controller.

Fortunately, the system successfully booted to Directory Services Restore Mode – which allowed me to online the D: disk, and successfully reboot my system.