cloudinit: RFC proposal for unwanted and unexpected regeneration of instance-id

[MAbeeTT]

Hello all,
I am Matias from Spain, raised in Argentina where I met PVE from
version 3 when trying to find an opensource KVM and container solution
for an internal lab.

After backup on proxmox PVE7 and restore in PVE8 [ 8.2.4 ] in my
personal lab I got new instance-id's hash for restored VMs.
Searching in the source code I see the root cause is the commit
cloudinit "pass through hostname via fqdn field" [0].

In certain conditions with the change in the commit without user
intervention in the VM a new key fqdn is created for the userdata, the
userdata info feeds the hash[1][2] which is in fact the value for the
key instance-id[3] of the meta-data file.

With a new instance-id the cloud-init agent in the VM takes the
"per-instance" configuration and actions, instead of the "per-boot"
configuration[4].
This is a problem not limited to new ssh keys, because users could
generate VM templates with specific actions to be triggered only with
a new VM/instance.

I propose you for future releases using only user explicit setup
options related with cloudinit setup (name, sshkeys, cipassword), I
mean explicit and ignore default values.
So in case of future changes as the referred commit there will not be
new instance-id as the user does not generate explicitly new cloudinit
source of info, then no new instance, no surprises for VM
administrator.

I am far away from being a Perl  developer, but I can put my best
effort during my spare time.
Anyway I would like to know what you think since what I am proposing
changes the current behaviour of PVE cloudinit, maybe these changes
could be part of PVE 9?

Thanks for your attention,

Regards,

Matias Pecchia

[0]: https://git.proxmox.com/?p=qemu-server.git;a=commitdiff;h=3e546c5ada47da8434bb58d27a3aa7d9823e7fa4
[1]: https://git.proxmox.com/?p=qemu-server.git;a=blob;f=PVE/QemuServer/Cloudinit.pm;h=abc6b1421b38c67f3de46ea075d5f8ac2fe599ef;hb=1c5001c2e7f8b73cdcf192d23714985eaddc17ed#l497
[2]: https://git.proxmox.com/?p=qemu-server.git;a=blob;f=PVE/QemuServer/Cloudinit.pm;h=abc6b1421b38c67f3de46ea075d5f8ac2fe599ef;hb=1c5001c2e7f8b73cdcf192d23714985eaddc17ed#l481
[3]: https://git.proxmox.com/?p=qemu-server.git;a=blob;f=PVE/QemuServer/Cloudinit.pm;h=abc6b1421b38c67f3de46ea075d5f8ac2fe599ef;hb=1c5001c2e7f8b73cdcf192d23714985eaddc17ed#l476
[4]: https://cloudinit.readthedocs.io/en/latest/explanation/boot.html#first-boot-determination


-- 
             .::MAbeeTT::.

 mabeett [at] gmail [ dot] com