OpenStack VM File System Error on reboot and nova rescue Cannot rescue a volume-backed instance (HTTP 400)

Openstack VM's File system went into read-only mode and rebooted it. After the reboot I'm getting grub menu and auto booting from the Kernel and seeing only blank screen in Openstck dashboard console.

I tried nova rescue but failed with below error,

cannot be rescued: Cannot rescue a volume-backed instance (HTTP 400)

I did edited the grub and enetered single/rescue mode to fix the file system error but still I'm getting blank screen after ctrl+x in grub edit. I want to bring up the vm instance and how do I fix the file system error.

File system error happened as of vm's backend storage, ceph sds node's all went down as of power failure and restored back.

I'm using RHOSP 13 and VM's image is RHEL 7.

I did alternate way to get into rescue mode and fixed the file system error.

1. ssh to compute Host of the instance and attach ISO image to the instance as it's backend is KVM (inside the file point the cdrom to ISO image location and boot dev to cdrom using virsh edit)

virsh edit vmname

2. Make the instance to active state from openstack cli command

nova reset-state --active instancename

3. Start the VM from compute Host

virsh start vmname

4. Get into openstack dashboard console and repair the file system accordingly and shutdown the instance

• Troubleshooting

• Rescue mode

• continue to shell

• vgscan -v

• vgchange -a y

• lvscan

• e2fsck /dev/xxx or xfs_repair /dev/xxx

5. From openstack cli start the instance normally after file system fix

nova start instancename