Downgrade issue.

Hi Prithivi Rajan

Thank you for sharing the details.

The boot issue you encountered after downsizing the VM from E32s v3 → E16s v3, where the system dropped into /sysroot/, typically indicates that the operating system could not properly mount or initialize the root filesystem after the hardware change. This behavior is commonly seen on Linux-based VMs during resize operations.

Below are the steps and considerations to help identify and avoid such issues:

1.Verify VM Size Compatibility

Please ensure that the target size (E16s v3) is available in the same Azure region and physical cluster where the current VM is hosted. If the SKU is not available in your cluster, the resize may allocate the VM on different hardware, causing the OS to fail during the boot process.

Reference: Change the size of a virtual machine

2.If the resize was performed while the VM was running, inconsistent hardware mapping can occur. Performing the resize using the below sequence avoids such issues:

stop (deallocated) >> Resize the VM >> Start the VM.

3. Enable boot diagnostics on your VM to gather information on why the VM is failing to boot. You can find logs and screenshots in the Azure portal under your VM’s ‘Boot diagnostics’ section.

Reference: https://dori-uw-1.kuma-moon.com/en-us/troubleshoot/azure/virtual-machines/windows/boot-diagnostics

4.Check the Activity Logs around the time of the failure, as well as any alerts or notifications that might give insight into what went wrong during the boot process.

Reference: https://dori-uw-1.kuma-moon.com/en-us/azure/azure-monitor/platform/activity-log?tabs=log-analytics

5.Ensure the OS disk is not corrupted and there are no pending issues with the disk itself. You could also attempt to repair the disk from within Recovery mode.

Reference: https://dori-uw-1.kuma-moon.com/en-us/troubleshoot/azure/virtual-machines/linux/troubleshoot-recovery-disks-linux

To know more understanding about the issue, please provide below details.

1. What exact error message do you see when the VM fails to boot?
2. What Linux distribution and version is running?
3. Have you checked if the VM size is available in your selected Azure region?
4. Did you make any configuration changes to the VM or the disk prior to attempting the downgrade?
5. Are there any specific applications or workloads running on the VM that might influence the downgrade attempt?
6. Exact Serial Console and Boot diagnostics screenshot/error message? (Azure Portal → VM → Serial Console)

Additionally, please check private message and provide necessary details