When booting the VMware ESXi host, you will see a < Shift+R: Recovery mode > prompt in the bottom right corner of the Loading VMware ESXi screen. Do you know what this feature does?
VMware ESXi recovery mode is used to roll back an ESXi host. Once you encounter any problems after an ESXi upgrade, you can roll back the ESXi host to a previous version through VMware ESXi recovery mode.
However, this feature is not perfect and you still need to use it with caution. In this article I will introduce how to roll back a host in VMware ESXi recovery mode.
When to use ESXi recovery mode
As I mentioned, VMware ESXi hypervisor recovery mode is used to roll back the ESXi host to a previous version. So to figure out when to use ESXi recovery mode, first you need to figure out when is it necessary to downgrade a VMware ESXi host?
Actually, there are only a few cases where you may need to downgrade your ESXi host back to a stable version. For example:
- some of your services or software are not compatible with the new version
- you are working on some tests that requires an older build
- you encountered some errors during the update
- it’s easier for you to roll back ESXi version than to reconfigure an ESXi host
However, this feature isn’t perfect and you may still run into some issues after downgrading, for example, losing important host configurations. Therefore, please make sure you know what will happen afterwards, and be prepared for it.
Prepare for VMware ESXi host downgrade
Verify installed versions: VMware ESXi recovery mode can only downgrade ESXi host to an installed previous version, not any random previous version. Therefore, before you start, you have to make sure that you have a previous version installed, or you will just get a “No alternative hypervisor” alert.
You can run the following command to verify the installed versions:
tail -2 /*bootbank/boot.cfg
Check the compatibility: Every update brings changes or new features. Therefore, it is important to check the compatibility in advance. Do not upgrade to a new version until you are sure that it is stable enough and can be used normally.
Backup ESXi host configuration: If you don’t want to reconfigure your ESXi host, it is still necessary to back up VMware ESXi host configuration to avoid loss or increase efficiency.
Backup and power off VMs, or migrate them to another host: VMs contain many important business data. Therefore, to avoid unexpected losses, please backup all VMware ESXi VMs, or migrate all VMs to another secure host before performing a downgrade.
How to roll back VMware ESXi host in recovery mode
1. Power on the VMware ESXi host. Press Shift+R before the loading bar completes.
2. Now you can see the installed hypervisor versions, and a warning below. Press Y to roll back to the previous version.
3. Press Enter to boot, or wait for the automatic boot countdown.
4. Wait for the process. When it finishes, you can see that the host has reverted to the previous version.
If you updated to a new version and are experiencing some compatibility issues or older build requirements, VMware provides such a rollback feature of VMware ESXi recovery mode. In this article, I introduced what is VMware ESXi recovery mode, when and how to use it and what to prepare in advance.
Before you perform risky operations like downgrading the host, backup is necessary to avoid unanticipated data loss. On this issue, compare to native VMware backup solutions, some dedicated backup tools may help you better and increase your work efficiency.
