Hi,
if you are doing a minor upgrade, you don't need to, because the relevant services will reload/restart gracefully after the upgrade via postinst hooks. That said, if you need new QEMU/LXC-specific features for the guests you need to restart them afterwards. If you do a kernel upgrade, it's recommended to reboot the host afterwards.
If you are doing a major version upgrade (not to be done via UI!), then yes, all guests need to be migrated to other cluster nodes or stopped. See https://pve.proxmox.com/wiki/Upgrade_from_6.x_to_7.0 for the full guide.
Okay thank you. this is what is available for updates right now. So a reboot would probably be needed because of the kernel update, so I may as well stop the VM's before the update?
Okay thank you. this is what is available for updates right now. So a reboot would probably be needed because of the kernel update, so I may as well stop the VM's before the update?
Sure, you can do that. But it's not required, and the reboot after a kernel upgrade doesn't need to be immediate (but if you can, no need to wait either).