Kubectl: Feature Request: Support $HOME/.kube/config.d/*

[omeid]

Greetings!

kubectl already allows defining multiple clusters and users in $HOME/.kube/config however editing this file by hand or even by tools is a bit cumbersome.

If kubectl supported loading multiple config files from $HOME/.kube/config.d/ it would make dealing with different cluster configurations much easier.

For example,

1. kubespray already generates a config file, but it is still not easy to use it if you already have a config file setup (kubernetes-sigs/kubespray/pull/1647).

2. aws eks cli already mutates the config file, but dealing with multiple clusters or updating this information requires way more mental overhead than it should require.

I would like to hear some feedback on this and whatever a pull request would be considered.

Many Thanks!

[weibeld]

Can't you do the same by having multiple config files in arbitrary locations and listing them in the KUBECONFIG environment variable?

[fejta-bot]

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[omeid]

/remove-lifecycle stale

[dwmkerr]

I'd be keen on this too.; If there are others who would like it then would be happy to put some time in for a PR

[omeid]

@weibeld Sure, but that wouldn't be the standard way and will be hard to convince tool vendors to follow through, it is also not exactly simple or easy approach.

[weibeld]

Sure, a $HOME/.kube/config.d/ would probably be more convenient, I just think maybe the Kubernetes maintainers might not want to introduce it, because they created the KUBECONFIG variable for the purpose of having multiple separate kubeconfig files.

What do you mean by "not the standard way"?

[omeid]

I think KUBECONFIG has it's own valid use, as means of overriding the default or active switch/context.

However, if kubectl context worked with $HOME/.kube/config.d/ files, tools (terraform, eks cli, kubespray, whatnot!) would emit their config files there with an appropriate name instead of trying to mutate $HOME/.kube/config (eks cli, atm), or worst overwrite it, or possibly leave it up to the user which has a cumbersome ux (what kubespray does atm).

What I mean by standard way is, asking a tool maintainer to support kubectl context is much more convincing than asking them to support some ad-hoc workflow.

Hope that makes it clear :)

[weibeld]

Is kubectl-switch a specific kubectl plugin or command?

In general, I wouldn't edit a kubeconfig file by hand, but use the kubectl config sub-commands. And for common tasks like changing the current context, or changing the namespace of the current context, I would use a tool like kubectx or something like these kubectl-ctx and kubectl-ns plugins.

[omeid]

Is kubectl-switch a specific kubectl plugin or command?

By kubectl-switch, I meant kubectl config set-context.

[dwmkerr]

@weibeld I would tend to automate using kubectl config too, but for the sake of organisation I can still imagine users who would like to arrange their own config files in a more structured manner, a bit like in a sources.d/ for apt. Even with kubectl config being able to specify that the config is written to a file inside of the config.d directory might be nice, meaning that you can automate the addition of configuration, but still ensure it ends up in a well organised location.

I have a few use cases for this, one is something like:

https://github.com/dwmkerr/terraform-aws-openshift

Where I'd like to run make infra to create the infrastructure, then make openshift to create openshift setup, but ideally then run make kube-config or something to create the config file. But ideally I'd love to keep this config separate from my main 'working' config.

[weibeld]

@dwmkerr It could indeed be more user-friendly to replace the KUBECONFIG variable with a .kube/config.d directory. So that the effective configuration would always be the merge of the default .kube/config file and all files in .kube/config.d (if present). The KUBECONFIG variable wouldn't be needed anymore. Or does someone see a use case where this approach is inferior to having the KUBEONFIG variable?

In the end, both approaches allow to do the same, but the directory approach frees you from having to deal with environment variables (which can be accidentally set and unset easily).

Currently, in your case, you would need to have your make kube-config create a .kube/aws-openshift config file for your cluster, and then set KUBECONFIG=~/.kube/config:~/.kube/aws-openshift. To make it persistent, you would have to add this to your ~/.bashrc, and then you have to hope that KUBECONFIG never gets changed by accident. So, yeah, just dropping the file into ~/.kube/config.d would definitely be easier. If you want to do a PR, it would certainly be a useful feature.

[dwmkerr]

Cool, I've got time this week so will aim to do it then 😄

[dwmkerr]

FYI I've created the design document and raised the feature request in the appropriate location (I think!) and mentioned this issue there, so I believe this issue can be closed now as it is linked to be the new feature request.

Design Document PR

https://github.com/kubernetes/kubernetes/issues/80120

[omeid]

I closed this issue under the impression that you have opened a pull request, now after some looking into this again, I am not sure that is the case. Is this issue not the right way to go about discussion whatever something is up for consideration or not?

I don't understand why an issue related to kubectl needs to be opened against kubernetes or community. Can you please help me understand?

[dwmkerr]

Hi @omeid honest I found the guide for contributing quite confusing, I was following the instructions here:

https://github.com/kubernetes/community/blob/master/sig-cli/CONTRIBUTING.md

I followed the instructions which involved creating the design doc, opening an issue on staging etc, it's quite a complex process so far, and I'm not sure the issues are even being seen...

[cblecker]

@dwmkerr if you're not getting responses from sig-cli, they list ways you can escalate for attention: https://github.com/kubernetes/community/blob/master/sig-cli/CONTRIBUTING.md#general-escalation-instructions

[dwmkerr]

Hi @cblecker thanks for the tips! Just pinged on the group, I've tried slack with no joy, but let's see what the group says. Really appreciate the help!

[bgrant0607]

There's a lot of history here:
https://github.com/kubernetes/kubernetes/issues/9298
https://github.com/kubernetes/kubernetes/issues/10693
https://github.com/kubernetes/kubernetes/issues/20605
https://github.com/kubernetes/kubernetes/issues/30395
https://github.com/kubernetes/kubernetes/pull/38861
https://github.com/kubernetes/kubernetes/issues/46381

And it would probably need to be respected by API client libraries, not just kubectl.

[seans3]

/sig cli
/sig apimachinery
/area kubectl
/kind feature

[seans3]

/sig api-machinery

[dwmkerr]

Hi @seans3 - thanks I saw your message for the SIG meeting, I'll join in the discussion! Yes I hadn't realised just quite how much history there is, wow!

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[seans3]

/remove-lifecycle stale

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[omeid]

/remove-lifecycle stale

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[omeid]

/remove-lifecycle stale

Still want this feature.

[BenTheElder]

/lifecycle frozen

[eddiezane]

/priority backlog

[pwittrock]

Is this answer sufficient: https://stackoverflow.com/questions/46184125/how-to-merge-kubectl-config-file-with-kube-config/46184649#46184649 ?

[BenTheElder]

@pwittrock the problem with actively mutating a single file is that we have to do the locking to avoid race conditions
The locking is known to be problematic though ...

If we could support a config.d and then a seperate file for just the current-context most cluster management tools would probably manage their own kubeconfig files without fear of racing with other tools.

see also: https://github.com/kubernetes/kubernetes/pull/92513

EDIT: racing on current-context is much less problematic than racing on the credentials etc. and possibly wiping out another cluster.
EDIT2: I know about KUBECONFIG env being allowed to contain a list, but this also has bad UX because then users need to ensure they set this across all their shells / environments. This is why most tools write to the default file.

[pwittrock]

What if we were to add a flatten command which performed the locking?

The challenges with supporting config.d is that it wouldn't be supported by plugins, controllers, etc that didn't have the code compiled in. @ahmetb was able to bring up some cases where users could end up using different contexts or clusters between plugins for instance, as the plugin would use just the kubeconfig, and kubectl would use the config.d -- e.g. the user could run kubectl get deploy to see the deployments, and then run some plugin kubectl plugin delete-all-deploy, expecting the kubectl get deploy Deployments to be deleted, but actually end up using a different resolved kubeconfig to talk to another cluster.

A possible solution to this would be to enable the feature with a flag --use-kubeconfig-d and rely on plugins to fail parsing the flag.

Another solution could be to have the KUBECONFIG env var support globs, so you could specify KUBECONFIG=$HOME/.kube/config:$HOME/.kube/config.d/*. Would need to check and make sure the existing parsing logic would fail on this.

EDIT: I see the issue about KUBECONFIG env. Users may be running different versions of kubectl across different environments as well, leading to the config.d feature being inconsistently supported. If we want consistency across tools and environments, I don't think we can add new capabilities to how things are resolved.

EDIT 2: The support issue also impacts using different versions of kubectl. I know gcloud provides a dispatcher that matches the version of kubectl to a cluster. There would likely be issues if it read the config.d, then chose to dispatch to a kubectl version that didn't support config.d.

WDYT?

[BenTheElder]

If we kept current-context specifically in the kubeconfig file specified by the existing rules then those tools would at worst be pointed to a nonexistent context and do nothing? (Since the context name would refer to one stored in some file they don't yet read)?

Most tools get the (possibly broken) locking by importing client-go.

A glob in KUBECONFIG env would be no less breaking that supporting a config.d? Tools would still need to be updated to read it for the problem scenario you outlined.

[BenTheElder]

For plugins, kubectl could pass a fully resolved KUBECONFIG list value / env based on the files discovered when calling them.

Ditto for the dispatcher.

[pwittrock]

This might be easier on VC

[BenTheElder]

Forgot to post back here: We spoke over VC and hashed it out, I intend to have a short doc ready to discuss at the next SIG CLI meeting.

[omeid]

@BenTheElder Can you link me to the CLI meeting please?

[eddiezane]

@omeid https://github.com/kubernetes/community/tree/master/sig-cli#meetings

[brianpursley]

One challenge with multiple configs is that the config file currently stores two types of information:

1. The definition of clusters, users, and contexts
2. Which context is your "current context" (what gets set when you run kubectl config use-context)

If there are multiple configs, how will kubectl interpret the current-context that is stored within multiple configs. Or if you run kubectl config use-context, where will kubectl store the current context that you switch to?

For example, consider a config file that looks like this:

apiVersion: v1
clusters:
- cluster:
    certificate-authority-data: ...
    server: ...
  name: cluster1
- cluster:
    certificate-authority-data: ...
    server: ...
  name: cluster2
contexts:
- context:
    cluster: cluster1
    user: user1
  name: context1
current-context: context1
kind: Config
preferences: {}
users:
- name: user1
  user:
    client-certificate-data: ...
    client-key-data: ...
    token: ...
- name: user2
  user:
    client-certificate-data: ...
    client-key-data: ...
    token: ...

To me, it seems like current-context and preferences should not be included in this config. They should be in a separate config file meant just for state, and there can only be one of those. Then you can have N number of configs that just contain the rest of the stuff: clusters, users, contexts, because those are just defining things that are available to use.

Anyway, this is something I've thought about in the past and thought it made sense to mention it here. I think kubectl will need to handle how current-context will work in a multi-config scenario.

[BenTheElder]

Sorry this fell by the wayside, I have not gotten to any real development lately ... swamped in reviews etc. 😞

@brianpursley this was part of our thinking as well ... only the existing location should have current-context / preferences, potentially with some validation warning / error-ing if present in config.d 👍

[brianpursley]

@BenTheElder sorry I should have read back before I commented. It looks like the current context issue has already been brought up. This issue was mentioned today in the sig cli meeting and I wanted to add this concern, but it sounds like you guys already covered it. 👍

[omeid]

To me, it seems like current-context and preferences should not be included in this config. They should be in a separate config file meant just for state, and there can only be one of those.

Also ideally, the other, non-state, config files should be restricted to 1 cluster per file to avoid any confusion and conflict in the future.

[morlay]

I use this script to load all kube config 🤣

export KUBECONFIG=$(echo $(ls ~/.kube/config.d/*) | sed 's/ /:/g')