Hi,
We don’t have a procedure for this specific use case. Zombie VMs are meant to be a warning of a VMs that need manual clean-up, not to be re-imported. Ideally, you should create a new VM from scratch.
Having said that, you could try 2 things to recover that old VM:
Change the vm name in the hypervisor to anything other than ‘one-*’. This way, OpenNebula will detect it as a wild VM instead of a zombie VM. A wild VM can be imported, but it will have limited support. The images and vnets will not be associated to it, you will have limited life-cycle control, etc.
Edit the database to insert the individual row into the ‘vm_poll’ table. The onedb fsck tool will try to fix some common inconsistencies, but you should plan for the worst: do backups.
Again, let me be clear on this: this is not supported, things are likely to break. Do not modify or backup the DB while OpenNebula is running. Don’t forget to backup!
Good luck