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Given that Docker images don't contain Linux kernel, when they are run in the host with a different Linux distribution they can get possibly different kernel version from the one shipped with the full (non-Docker) distribution.

How can a distribution vendor support their OS when it is run in a Docker container, given the variation in the host kernels? Do they require it to be run on the host with the same flavor/version (for example Ubuntu 15.04 on Ubuntu 15.04)?

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Seems like you're making an assumption that kernel version matters. Surely there are cases where it does, but in the vast majority of cases, it does not matter.

Of course like any well-managed system, you should ensure you have tight control on your host systems as well as your application containers, and that your testing environment matches your prod environment.

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  • When you have a commercial version (say RHEL) and have some issue, when you raise a support ticket, you of course specify the version you have. Then you say, by the way, I am running this with the Ubuntu kernel, which may be even the same major/minor version, but it has different bits? – Ivan Oct 7 '15 at 0:34
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I guess you need support from the application vendor, not the OS one. As it's not the OS running in docker but the app. You will probably find some applications docker containers for most of the applications you need, and they will probably be certified for some OSes (thus forcing you a docker version) if you have support from the vendors.

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  • But the app is running within the OS. For example, for the official Postgres container, the first line of its Dockerfile is: 'FROM debian:jessie' – Ivan Oct 7 '15 at 17:14
  • All this means is the way all this is marketed, you build container once and it can run on any docker host, isn't really true in practice, in enterprise environments -- looks like you can only run a container on a host with the same OS flavour/version that the container image is based on. – Ivan Oct 7 '15 at 17:19
  • Well I agree with you. But you have to differentiate between commercial products like Oracle/IBM/Red Hat/other vendor and community based ones like PostgreSQL for example. I guess for PostgreSQL there's no real support behind these images, you just download them and hope you won't have any issue with them. For Oracle as opposite they ask you to follow a detailed procedure, for example: docs.oracle.com/cd/E37670_01/E37355/html/ol_docker.html public-yum.oracle.com/docker-images I'm not trying to be exhaustive though. – Pierre-Alain TORET Oct 7 '15 at 21:26

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