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Comment by CoolCold | Hacker News Reader

I'm not quite sure what's your question here? Very much similar to any other system which needs to reboot and you getting ready to these reboots in advance.

To some extent, of course things like vSphere/Virtuozzo and even LXD/Incus, and even simple Qemu/Virsh systems can do live migration of VMs, so you may care less on preparing things inside VMs to be fault taulerant, but to some extent.

I.e. if your team do run PostgreSQL, your run it in cluster with Patroni and VIPs and all that lovely industry standard magic and tell dev teams to use that VIP as entry point (in reality things bit more complicated with Haproxy/Pgbouncer on top, but enough to express the idea).

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I missed the part that Incus supports clustering, for some reason I thought it's single node only.

I'm not sure that clustering goes beyond "multiple hosts with single API to rule them all" - thus I assume when physical node needs maintenance, it won't magically migrate / restart VEs on other cluster members. May be wrong here.

P.S. Microcloud tries to achieve this AFAIR, but it's from Canonical, so on LXD.

Okay then my question still stands. You are saying "similar to any other system which needs to reboot", but this is nowhere near similar to something like k8s, which has 1st class support for this. You cordon the node you are about to take off for maintenance, kubernetes automatically redistributes all the workloads to the other nodes, and after you are done you uncordon the node.

How does this look with Incus? Obviously if the workload you are running has some kind of multinode support you can use that, but I'm wondering if Incus a way to do this in some kind of generalized way like k8s?

But I did some more reading, there seems to be support for live migration for VMs, and limited live migration for containers. Moving stopped instances is supported for both VMs and containers.

I think what you are asking falls into "cluster member evacuation and re-balancing" [0], combined with live migration [1] with minimal downtime.

[0] https://linuxcontainers.org/incus/docs/main/howto/cluster_ma...

[1] https://linuxcontainers.org/incus/docs/main/howto/move_insta...

Amazing, exactly what I was looking for, thank you.

Thank you!

Indeed, container live migration is limited and a bit unclear on "network devices" - bridged interface is network device or not?

Bit ironic, that even with using CRUI, which AFAIK was created by the same Virtuozzo guys which provided OpenVZ back then, and that VEs could live migrate, was personally testing it in 2007-2008. Granted, there we no systemd by that days, if this complicates things. And of course required their patched kernel.

> Live migration for containers For containers, there is limited support for live migration using CRIU. However, because of extensive kernel dependencies, only very basic containers (non-systemd containers without a network device) can be migrated reliably. In most real-world scenarios, you should stop the container, move it over and then start it again.

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