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Posts Tagged ‘Kubernetes

Sharing Process Namespace in Kubernetes

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Kubernetes pods allow cooperation between containers, which can be powerful, but they have always used isolated process namespaces because that’s all Docker supported at the time Kubernetes was created. This prevented one from doing things like signalling a main process from a logging sidecar, for example.

I’ve been working with SIG Node to change this, though, and Process Namespace Sharing has been released as an Alpha feature in Kubernetes 1.10. Compatibility within an API version (e.g. v1.Pod) is very important to the Kubernetes community, so we didn’t change the default behavior. Instead we introduced a new field in v1.Pod named ShareProcessNamespace. Try it for yourself!

Pods exist to share resources, so it makes sense to share processes as well. I wouldn’t be surprised if process namespace sharing became the default in v2.Pod.

I’d love to hear what you think and whether this feature helps you. Let me know in Kubernetes feature tracking or the comments below.

Written by Lee Verberne

2018-04-12 at 12:13

Posted in Kubernetes

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Alpine Linux doesn’t work with KubeDNS. Sad.

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I was really getting into building docker images from Alpine Linux. I like its philosophy and general 5MB-ness. I discovered tonight, however, that its libc resolver has some significant differences from that of GNU libc. Most notably, the resolver queries all nameservers in parallel and doesn’t support a search path.

I don’t care that much about the search path for these images. Querying the nameservers in parallel sounds great, but unfortunately Kubernetes’ KubeDNS configures a resolv.conf that expects in-order querying. Only the first nameserver will respond with cluster local records.

Oh well, guess I’ll switch everything back over to debian…

Written by Lee Verberne

2015-08-26 at 21:27

Posted in Containers

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