Edge ganeti clusters were setup with Buster from the start, but eqiad/codfw are still in need of an update:
[x] Import the last backport of ganeti 2.16.0-1~bpo9+1 to a repo component ganeti/216 (stretch)
[] add the repo component to the Ganeti hosts
[] Upgrade a single node to 2.16 and test (verify, verify-disks, create new VM, start/stop, migrate VM back & forth)
[] Upgrade remaining stretch nodes to 2.16
[] Run gnt-cluster renew-crypto (for SHA256 compat) https://bugs.debian.org/cgi-bin/bugreport.cgi?bug=907569
[] Run gnt-cluster upgrade --to 2.16
[] Run gnt-cluster verify, verify-disks, migrations back and forth, stop/start VMs
[] For each stretch host:
* Empty a node of VMs with gnt-node migrate / gnt-node evacuate -s
* Reimage to buster (which also brings new qemu compared to before)
* Re-add the node and test
* Move back VMs