Kyle Gleed, Sr. Technical Marketing Manager, VMware

If you are running the free version of ESXi (aka ESXi Hypervisor) then you'll want to be aware of a critical issue that surfaces after upgrading to 5.0 Update 1.  I want to stress this only applies to people runing the free ESXi version.  If you're ESXi hosts are licensed this issue does not affect you.

There were some changes made in the way the ESXi APIs are accessed in Update 1 that unfortunately breaks the VM Auto Start feature in the free ESXi version.  Please note that this issue only affects the free ESXi version and it was not intentional.  I've heard some people making claims that VMware did this on purpose as a way to further limit the free ESXi version, this is not true.  I'm not aware of a workaround, but many customers have been able to leverage the dual-image architecture of ESXi in order to roll-back to the pre-upgrade state.   

To roll-back to the pre-upgrade image:

Using the DCUI is the supported and recommended way to rollback your ESXi image.  From the ESXi host console reboot the host, at the very beginning of the boot, when you see the boot options prompt (<ENTER: Boot>), press SHIFT+R to enter recovery mode, and when prompted answer "y" to confirm that you want to revert back to the previous image profile.


ESXi Shell
If you don't have access to the host console you can still revert back to the pre-upgrade image profile by editing the "boot.cfg" files located in the /bootbank and /altbootbank directories (yes, you have to edit both files).  Note that manually editing these configuration files is not supported by VMware, so you never want to do this on a production ESXi hosts.  However, because this issue only affects the free ESXi version, and because I've had a couple folks ask how this can be done I wanted to go ahead and show you.  Assuming the last line in your /bootbank/boot.cfg shows "updated=2" and the last line in your /altbootbank/boot.cfg shows "updated=1", simply reverse the numbers so that /bootbank/boot.cfg is "updated=1" and /altbootbank/boot.cfg is "updated=2".  For example:

/bootbank/boot.cfg = "updated=2"
/altbootbank/boot.cfg = "updated=1"

/bootbank/boot.cfg = "updated=1"
/altbootbank/boot.cfg = "updated=2"

After editing the boot.cfg file in both the /bootbank and /altbootbank reboot your host for the change to take affect.  Having reversed the order of the bootbanks in the boot.cfg file the host will now reboot off the pre-upgrade image. 

Keep in mind that it is always a good idea to take a backup of your host (vicfg-cfgbackup) before attempting to revert your image profile.  Again, please note that the supported/recommend method is using the DCUI.  Only resort to editing the boot.cfg files for noncritical hosts such as those used in home labs and other test and development environments as any mistakes will very likely render your host unable to boot.

Many thanks to William Lam (@lamw) for his help on this blog…

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About the Author

Kyle Gleed

Kyle Gleed is a Group Manager within VMware’s Integrated Systems Business Unit (ISBU) where he leads a team focused on the adoption and deployment of the solutions and capabilities of the Software-Defined Data Center. Follow Kyle on twitter @Kyle_Gleed