I recently had an issue where I couldnt get into one of my ESXi Servers as I did not know the Password. I could get into vCenter and so forced a reset of all root user password via Host Profiles.
In vCenter, select Home > Host Profiles
Select Extract profile from a host..
Select one of your Hosts
Give the Host Profile a name – I used reset-esxi-root-password
Now, select the Host Profile, select Actions and Edit Settings..
Select your Profile and click Next
To Change Root Password, the only section that needs to be selected is: Security and Services > Security Settings > Security > User Configuration > root
Select Fixed password configuration from the Password dropdown
Enter and Confirm Password > Click Finish
Ensure the Profile is selected and click Actions > Attach Hosts and Clusters
Select relevant Hosts or Clusters and use Attach to move them across
Select Finish on the Customize Hosts screen
Select Actions > Check Host Profile Compliance
We can see we have 2 Hosts in Non-Compliance
Go to Actions > Remidiate
Select the Hosts you want to remediate and click Next (This is my lab so I can do these at the same time)
Select Pre-Check Remediation
I have Reboot hosts which require it ticked and select Finish
I can now log into my ESXI Hosts with the new Password