[lxc-users] Upgrading host and containers : in which order ?

[phep]

Hi,

Pretty much every thing's in the subject line : we've got a host running 
Debian Jessie and LXC 1.0 with a handful of containers in the same Debian 
version that we all need to upgrade to Debian Stretch with LXC 2.0. By the 
way, hosts and containers are using systemd as init system, if this matters.

I'm wondering which migration route I should take : migrate host first or 
containers first ?

Actually, I already had to upgrade a container and that did not bring any 
major problem, except for the presence of this systemd message in its logs:
systemd-udevd.service: Cannot add dependency job, ignoring: Unit 
systemd-udevd.service is masked.

Thanks in advance for every piece of advice,

phep