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Securing Services with Rootless Containers

112 points by speckx

by raesene9

2 subcomments

Rootless helps, but less now that it used to (pre-2026). There have been a lot of local privilege escalation vulnerabilities in the Linux kernel (dirtyfrag, fragnesia, CIFSwitch et al) and several of those can be repurposed as container breakouts.
As a result, if you're looking for good security isolation, I'd say a (Micro)VM is a better option. The other route is hardening down your container runtime with seccomp/AppArmor/SELinux but that can be a tricky game.

by seemaze

1 subcomments

The '--userns=auto' argument is a useful isolation method in both rootless and rootful Podman containers. This allows rootful Podman to orchestrate privileged capabilities while running the container processes in an unprivileged namespace.
See the discussion here:
https://github.com/podman-container-tools/podman/discussions...

by kayson

5 subcomments

I'd still rather use docker. I don't mind that the daemon runs as root because there are some things that you need root for anyways! Like binding to privileged ports or setting up networks (use `internal: true` and the daemon will automatically set up iptables rules that limit traffic).
I deploy docker compose files with ansible so everything comes with built in security defaults like rootless, dropped caps, no new privileges, etc. I wish more containers supported running read only (its usually pretty easy to add, just overlooked) and distroless (common for go apps, less so otherwise).
There was a pretty good comment on reddit a while back with a list of hardenings for compose files [1]
1. https://www.reddit.com/r/selfhosted/comments/1pr74r4/comment...

by Narushia

0 subcomment

The .container units get the job done, but if you want to manage a stack of containers and are familiar with Kubernetes, or just like YAML, I recommend using the .kube units instead.[1]
[1]: https://docs.podman.io/en/stable/markdown/podman-kube.unit.5...

by samhclark

0 subcomment

Funny timing! I just finished migrating my NAS containers all to be rootless last weekend.
"Migrating" because secrets management was a bit of a pain. I ended up with pretty close to the same design as this article though. (I put an extra layer of complexity in mine, we'll see if I regret it)
Along with the other folks in this thread, I don't think we can stop at rootless in 2026. But I'm optimistic that dropping in libkrun as the runtime will be an easy next step, given its integration with podman (--runtime=krun).
If the author tackles that next, I'd be interested in reading about it

by Lucasoato

0 subcomment

Is there any other reference regarding how safer we are by using rootless vs rootful containers?

by firasd

0 subcomment

Interesting... yeah if you think of Docker as an easy way to setup environments that's one thing but if you are intending airtight isolation so processes inside Docker can't "escape" most conventional use cases / discourse haven't really focused on that I think

by ranger_danger

7 subcomments

Personally I still think this is not enough, and we really need full generalized (not AI-only) microvm support built into docker/podman, like yesterday.
Currently it's difficult to even get a hold of a properly configured minimal kernel (or time-consuming to try to build one) and all the right command-line incantations to even start a one-off microvm using say, qemu, with all the proper storage/networking/etc. bits one needs for production environments. Plus you need to keep that kernel updated very regularly.
I know there's projects like smolvm that try to make this simpler, but I've had some major problems with those solutions as well, and I just feel like the big boys need to step up and support this directly by now.

by FooBarWidget

1 subcomments

Rootless containers have privilege escalation risks of their own. The problem is the unprivileged_userns_clone sysctl, which rootless containers rely on, has historically been a big source of local privilege escalations. The most recent attack I'm aware of is CIFSwitch.

by croemer

0 subcomment

by Shreysid

0 subcomment