Merge existing configuration files with files created by configmap, or multiple configmaps

[Dmitriy Shulyak]

Hi folks,

I am trying to come up with solution for the problem when one may need to merge multiple configuration files that are stored in different

configmaps, or they are pre-created, and stored in image.

In image I have existing tree, like

/etc/configs

└── config1

And the following tree will be mounted by k8s configmap

/etc/configs

└── config2

As a result - existing configuration files won't be visible, as long as configmap volume is mounted.

I thought about several solutions for this problem:

1. Mount each file from configmap separately (this information should be available when mounts are created in kubelet)

- it might be a problem with big amount of keys in configmap, and thus shouldnt be default behaviour

2. Use overlayfs/aufs and make necessary changes in docker

- still tricky to merge multiple configmaps into single directory

3. Mount configmap to another directory and copy them using init-container

- is it possible to mount configmap in init-container?

I believe this should be common thing, and probably someone already thought about it. 

Is there any plans how to tackle this case, or maybe there is already a solution?

[Eric Tune]

Let me see if I understand you correctly.

Are you talking about merging lines from two sources (image and configmap) into a single file, or putting two files from different sources into a single directory?

Are you trying to solve this for the general case, or for a specific application?

--
You received this message because you are subscribed to the Google Groups "kubernetes-dev" group.
To unsubscribe from this group and stop receiving emails from it, send an email to kubernetes-de...@googlegroups.com.
To post to this group, send email to kuberne...@googlegroups.com.
To view this discussion on the web visit https://groups.google.com/d/msgid/kubernetes-dev/5c462b3b-ac1a-46df-a19f-7b63e6e33226%40googlegroups.com.
For more options, visit https://groups.google.com/d/optout.

[Dmitriy Shulyak]

1st problem:

On the image we have /etc/nova/api-paste.ini which is generated during installation, and

other configuration files will be mounted using configmap. So somehow I want to "merge" configmap

with existing directory content.

2nd problem:

Mount /etc/rsyslog.conf

I want to propose: optionally copy data from image into configmap directory before that directory will be mounted

into container, but it will not solve 2nd use case.

Can someone suggest path to address this issues?

On Thursday, July 14, 2016 at 10:08:52 PM UTC+3, Dmitriy Shulyak wrote:

2nd, two files from different sources.

There is use case with openstack services, i will add details in the morning.

Sorry for confusion.

To unsubscribe from this group and stop receiving emails from it, send an email to kubernetes-dev+unsubscribe@googlegroups.com.
To post to this group, send email to kubernetes-dev@googlegroups.com.

[Dmitriy Shulyak]

FYI https://github.com/kubernetes/kubernetes/commit/06900a934dfa58c520e2d060088cf66d93e32020

[Eric Tune]

Feel free to file an issue in kubernetes/kubernetes about this.  I think you best solution right now is probably to mount your config files in separate volumes, and then use an init container to copy them to /etc before the main container runs.  Or, if you want dynamic updates, use a sidecar to watch for changes and copy the files.

FYI https://github.com/kubernetes/kubernetes/commit/06900a934dfa58c520e2d060088cf66d93e32020

To unsubscribe from this group and stop receiving emails from it, send an email to kubernetes-de...@googlegroups.com.
To post to this group, send email to kuberne...@googlegroups.com.

[Dmitriy Shulyak]

Using subPath it is possible to mount only single file, i added this info to configmap documentation [0]

0. https://github.com/dshulyak/kubernetes.github.io/blob/d58ba7b075bb4848349a2c920caaa08ff3773d70/docs/user-guide/configmap/mount-file-pod.yaml

[Eric Tune]

Awesome, thanks!