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How to get a unique MAC/DHCP IP for a Docker/Podman container without MACVLAN? (lemmy.blahaj.zone)

submitted 3 days ago by glizzyguzzler@lemmy.blahaj.zone to c/selfhosted@lemmy.world

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I have a bridge device set up with systemd, br0, that replaces my primary ethernet eth0. With the br0 bridge device, Incus is able to create containers/VMs that have unique MAC addresses that are then assigned IP addresses by my DHCP server. (sudo incus profile device add <profileName> eth0 nic nictype=bridged parent=br0) Additionally, the containers/VMs can directly contact the host, unlike with MACVLAN.

With Docker, I can't see a way to get the same feature-set with their options. I have MACVLAN working, but it is even shoddier than the Incus implementation as it can't do DHCP without a poorly-maintained plugin. And the host cannot contact the container due to the MACVLAN method (precludes running a container like a DNS server that the host server would want to rely on).

Is there a way I've missed with the bridge driver to specify a specific parent device? Can I make another bridge device off of br0 and bind to that one host-like? Searching really fell apart when I got to this point.

Also, if someone knows how to match Incus' networking capability with Podman, I would love to hear that. I'm eyeing trying to move to Podman Quadlets (with Debian 13) after I've got myself well-versed with Docker (and its vast support infrastructure to learn from).

Hoping someone has solved this and wants to share their powers. I can always put a Docker/podman inside of an Incus container, but I'd like to avoid onioning if possible.

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[–] glizzyguzzler@lemmy.blahaj.zone 3 points 2 days ago (1 children)

This was very insightful and I’d like to say I groked 90% of it meaningfully!

For an Incus container with its unique MAC interface, yes if I run a Docker container in that Incus container and leave the Docker container in its default bridge mode then I get the desired feature set (with the power of onions).

And thanks for explaining CNI, I’ve seen it referenced but didn’t fully get how it’s involved. I see that podman uses it to make a MACVLAN interface that can do DHCP (until 5.0, but the replacement seems to be feature-compatible for MACVLAN), so podman will sidestep the pain point of having to assign a no-go-zone on the DHCP server for a Docker swath of IPv4s, as you mentioned. Close enough for containers that the host doesn’t need to talk to.

So in summary:

I’ve got Docker doing the extent it can manage with MACVLAN and there’s no extra magicks to be done on it.
Podman will still use MACVLAN (no host to container comms still) but it’s able to use DHCP to get an address for the MACVLAN container.
If the host must talk to the container with MACVLAN, I can either use the MACVLAN bypass as you linked to above or put the Docker/Podman container inside an Incus container with its bridge mode.
Kubernutes continues to sound very powerful and flexible but is definitely beyond my reach yet. (Womp womp)

Thanks again for taking the time to type and explain all of that!

[–] litchralee@sh.itjust.works 1 points 2 days ago

Kubernetes does indeed have a learning curve, but it's also strangely accommodating for single-node setups which can then be expanded only by adding components, rather than tearing the whole thing down and starting again. In that sense, it's a great learning platform towards managing larger or commercial clusters, if simply to get experience with the unique challenges inherent to scaling up.

But that might be more of a !homelab@lemmy.ml point of view haha