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If you’re interested in supporting mybinder.org with cloud resources, financial resources, or human resources, please see the Support Binder page for how you can help. tl;dr: The 2i2c team is joining ...

### Context: At $WORK I am doing a lot of datascience work around Jupyter Notebooks and their ecosystem. Right now I am setting BinderHub, which is a service to start a Jupyter Notebook from a git repo in your browser. For setting up BinderHub I am using the BinderHub helm chart, and I was wondering how configuration changes are propagated from the BinderHub helm chart to the process running in a Kubernetes Pod. After going through this I can say I am not right now a great fan of Helm, as it looks to me like an unnecessary, overengineered abstraction layer on top of Kubernetes manifests. Or maybe it is just that I don’t want to learn the golang templating synthax. I am looking forward to testing Kustomize as an alternative, but I havn’t had the chance yet. ### Starting from the list of config parameters available: Although many parameters are mentioned in the installer document, you have to go to the developer doc at https://binderhub.readthedocs.io/en/latest/reference/ref-index.html to get a whole overview. In my case I want to set the `hostname` parameter for the Gitlab Repoprovider. This is the relevelant snippet in the developer doc: hostname c.GitLabRepoProvider.hostname = Unicode('gitlab.com') The host of the GitLab instance The string `c.GitLabRepoProvider.hostname` here means, that the value of the `hostname` parameter will be loaded at the path config.GitLabRepoProvider inside a configuration file. Using the yaml synthax this means the configuration file should contain a snippet like: config: GitlabRepoProvider hostname: my-domain.com ### Digging through Kubernetes constructs: Helm values files When installing BinderHub using the provided helm chart, we can either put the configuration snippet in the config.yaml or secret.yaml helm values files. In my case I have put the snippet in config.yaml, since the hostname is not a secret thing, I can verify with **`yq`** that it correctly set: $ yq --raw-output '.config.GitLabRepoProvider.hostname' config.yaml my-domain.com How do we make sure this parameter is properly applied to our running binder processes ? As said previouly this parameter is passed as a value file to **`helm`** (–value or -f option) in the command: $ helm upgrade \ binderhub \ jupyterhub/binderhub \ --install \ --version=$(RELEASE) \ --create-namespace \ --namespace=binderhub \ --values secret.yaml \ --values config.yaml \ --debug According to the helm documentation in https://helm.sh/docs/helm/helm_install/ the values file are concatenated to form a single object, and priority will be given to the last (right-most) file specified. For example, if both myvalues.yaml and override.yaml contained a key called ‘Test’, the value set in override.yaml would take precedence: $ helm install --values myvalues.yaml --values override.yaml myredis ./redis ### Digging through Kubernetes constructs: Secrets and Volumes When `helm upgrade` is run the helm values of type `config` are stashed in a Kubernetes secret `binder-secret`: https://github.com/jupyterhub/binderhub/blob/main/helm-chart/binderhub/templates/secret.yaml#L12 stringData: {{- /* Stash away relevant Helm template values for the BinderHub Python application to read from in binderhub_config.py. */}} values.yaml: | {{- pick .Values "config" "imageBuilderType" "cors" "dind" "pink" "extraConfig" | toYaml | nindent 4 }} We can verify that our hostname is passed to our Secret: $ kubectl get secret binder-secret -o yaml | yq --raw-output '.data."values.yaml"' | base64 --decode ... GitLabRepoProvider: hostname: my-domain.com ... Finally a configuration file inside the Binder pod is populated from the Secret, using the Kubernetes Volume construct. Looking at the Pod, we do see a volume called `config`, created from the `binder-secret` Secret: $ kubectl get pod -l component=binder -o yaml | grep --context 4 binder-secret volumes: - name: config secret: defaultMode: 420 secretName: binder-secret That volume is mounted inside the pod at `/etc/binderhub/config`: volumeMounts: - mountPath: /etc/binderhub/config/ name: config readOnly: true ### Runtime verification Looking inside our pod we see our hostname value available in a file underneath the mount point: oc exec binder-74d9c7db95-qtp8r -- grep hostname /etc/binderhub/config/values.yaml hostname: my-domain.com

If you’re interested in supporting mybinder.org with cloud resources, financial resources, or human resources, please see the Support Binder page for how you can help. tl;dr: The 2i2c team is joining the mybinder.

Reproducible, sharable, open, interactive computing environments.

### Context: At $WORK I am doing a lot of datascience work around Jupyter Notebooks and their ecosystem. Right now I am setting BinderHub, which is a service to start a Jupyter Notebook from a git repo in your browser. For setting up BinderHub I am using the BinderHub helm chart, and I was wondering how configuration changes are propagated from the BinderHub helm chart to the process running in a Kubernetes Pod. After going through this I can say I am not right now a great fan of Helm, as it looks to me like an unnecessary, overengineered abstraction layer on top of Kubernetes manifests. Or maybe it is just that I don’t want to learn the golang templating synthax. I am looking forward to testing Kustomize as an alternative, but I havn’t had the chance yet. ### Starting from the list of config parameters available: Although many parameters are mentioned in the installer document, you have to go to the developer doc at https://binderhub.readthedocs.io/en/latest/reference/ref-index.html to get a whole overview. In my case I want to set the `hostname` parameter for the Gitlab Repoprovider. This is the relevelant snippet in the developer doc: hostname c.GitLabRepoProvider.hostname = Unicode('gitlab.com') The host of the GitLab instance The string `c.GitLabRepoProvider.hostname` here means, that the value of the `hostname` parameter will be loaded at the path config.GitLabRepoProvider inside a configuration file. Using the yaml synthax this means the configuration file should contain a snippet like: config: GitlabRepoProvider hostname: my-domain.com ### Digging through Kubernetes constructs: Helm values files When installing BinderHub using the provided helm chart, we can either put the configuration snippet in the config.yaml or secret.yaml helm values files. In my case I have put the snippet in config.yaml, since the hostname is not a secret thing, I can verify with **`yq`** that it correctly set: $ yq --raw-output '.config.GitLabRepoProvider.hostname' config.yaml my-domain.com How do we make sure this parameter is properly applied to our running binder processes ? As said previouly this parameter is passed as a value file to **`helm`** (–value or -f option) in the command: $ helm upgrade \ binderhub \ jupyterhub/binderhub \ --install \ --version=$(RELEASE) \ --create-namespace \ --namespace=binderhub \ --values secret.yaml \ --values config.yaml \ --debug According to the helm documentation in https://helm.sh/docs/helm/helm_install/ the values file are concatenated to form a single object, and priority will be given to the last (right-most) file specified. For example, if both myvalues.yaml and override.yaml contained a key called ‘Test’, the value set in override.yaml would take precedence: $ helm install --values myvalues.yaml --values override.yaml myredis ./redis ### Digging through Kubernetes constructs: Secrets and Volumes When `helm upgrade` is run the helm values of type `config` are stashed in a Kubernetes secret `binder-secret`: https://github.com/jupyterhub/binderhub/blob/main/helm-chart/binderhub/templates/secret.yaml#L12 stringData: {{- /* Stash away relevant Helm template values for the BinderHub Python application to read from in binderhub_config.py. */}} values.yaml: | {{- pick .Values "config" "imageBuilderType" "cors" "dind" "pink" "extraConfig" | toYaml | nindent 4 }} We can verify that our hostname is passed to our Secret: $ kubectl get secret binder-secret -o yaml | yq --raw-output '.data."values.yaml"' | base64 --decode ... GitLabRepoProvider: hostname: my-domain.com ... Finally a configuration file inside the Binder pod is populated from the Secret, using the Kubernetes Volume construct. Looking at the Pod, we do see a volume called `config`, created from the `binder-secret` Secret: $ kubectl get pod -l component=binder -o yaml | grep --context 4 binder-secret volumes: - name: config secret: defaultMode: 420 secretName: binder-secret That volume is mounted inside the pod at `/etc/binderhub/config`: volumeMounts: - mountPath: /etc/binderhub/config/ name: config readOnly: true ### Runtime verification Looking inside our pod we see our hostname value available in a file underneath the mount point: oc exec binder-74d9c7db95-qtp8r -- grep hostname /etc/binderhub/config/values.yaml hostname: my-domain.com

### Context: At $WORK I am doing a lot of datascience work around Jupyter Notebooks and their ecosystem. Right now I am setting BinderHub, which is a service to start a Jupyter Notebook from a git repo in your browser. For setting up BinderHub I am using the BinderHub helm chart, and I was wondering how configuration changes are propagated from the BinderHub helm chart to the process running in a Kubernetes Pod. After going through this I can say I am not right now a great fan of Helm, as it looks to me like an unnecessary, overengineered abstraction layer on top of Kubernetes manifests. Or maybe it is just that I don’t want to learn the golang templating synthax. I am looking forward to testing Kustomize as an alternative, but I havn’t had the chance yet. ### Starting from the list of config parameters available: Although many parameters are mentioned in the installer document, you have to go to the developer doc at https://binderhub.readthedocs.io/en/latest/reference/ref-index.html to get a whole overview. In my case I want to set the `hostname` parameter for the Gitlab Repoprovider. This is the relevelant snippet in the developer doc: hostname c.GitLabRepoProvider.hostname = Unicode('gitlab.com') The host of the GitLab instance The string `c.GitLabRepoProvider.hostname` here means, that the value of the `hostname` parameter will be loaded at the path config.GitLabRepoProvider inside a configuration file. Using the yaml synthax this means the configuration file should contain a snippet like: config: GitlabRepoProvider hostname: my-domain.com ### Digging through Kubernetes constructs: Helm values files When installing BinderHub using the provided helm chart, we can either put the configuration snippet in the config.yaml or secret.yaml helm values files. In my case I have put the snippet in config.yaml, since the hostname is not a secret thing, I can verify with **`yq`** that it correctly set: $ yq --raw-output '.config.GitLabRepoProvider.hostname' config.yaml my-domain.com How do we make sure this parameter is properly applied to our running binder processes ? As said previouly this parameter is passed as a value file to **`helm`** (–value or -f option) in the command: $ helm upgrade \ binderhub \ jupyterhub/binderhub \ --install \ --version=$(RELEASE) \ --create-namespace \ --namespace=binderhub \ --values secret.yaml \ --values config.yaml \ --debug According to the helm documentation in https://helm.sh/docs/helm/helm_install/ the values file are concatenated to form a single object, and priority will be given to the last (right-most) file specified. For example, if both myvalues.yaml and override.yaml contained a key called ‘Test’, the value set in override.yaml would take precedence: $ helm install --values myvalues.yaml --values override.yaml myredis ./redis ### Digging through Kubernetes constructs: Secrets and Volumes When `helm upgrade` is run the helm values of type `config` are stashed in a Kubernetes secret `binder-secret`: https://github.com/jupyterhub/binderhub/blob/main/helm-chart/binderhub/templates/secret.yaml#L12 stringData: {{- /* Stash away relevant Helm template values for the BinderHub Python application to read from in binderhub_config.py. */}} values.yaml: | {{- pick .Values "config" "imageBuilderType" "cors" "dind" "pink" "extraConfig" | toYaml | nindent 4 }} We can verify that our hostname is passed to our Secret: $ kubectl get secret binder-secret -o yaml | yq --raw-output '.data."values.yaml"' | base64 --decode ... GitLabRepoProvider: hostname: my-domain.com ... Finally a configuration file inside the Binder pod is populated from the Secret, using the Kubernetes Volume construct. Looking at the Pod, we do see a volume called `config`, created from the `binder-secret` Secret: $ kubectl get pod -l component=binder -o yaml | grep --context 4 binder-secret volumes: - name: config secret: defaultMode: 420 secretName: binder-secret That volume is mounted inside the pod at `/etc/binderhub/config`: volumeMounts: - mountPath: /etc/binderhub/config/ name: config readOnly: true ### Runtime verification Looking inside our pod we see our hostname value available in a file underneath the mount point: oc exec binder-74d9c7db95-qtp8r -- grep hostname /etc/binderhub/config/values.yaml hostname: my-domain.com

### Context: At $WORK I am doing a lot of datascience work around Jupyter Notebooks and their ecosystem. Right now I am setting BinderHub, which is a service to start a Jupyter Notebook from a git repo in your browser. For setting up BinderHub I am using the BinderHub helm chart, and I was wondering how configuration changes are propagated from the BinderHub helm chart to the process running in a Kubernetes Pod. After going through this I can say I am not right now a great fan of Helm, as it looks to me like an unnecessary, overengineered abstraction layer on top of Kubernetes manifests. Or maybe it is just that I don’t want to learn the golang templating synthax. I am looking forward to testing Kustomize as an alternative, but I havn’t had the chance yet. ### Starting from the list of config parameters available: Although many parameters are mentioned in the installer document, you have to go to the developer doc at https://binderhub.readthedocs.io/en/latest/reference/ref-index.html to get a whole overview. In my case I want to set the `hostname` parameter for the Gitlab Repoprovider. This is the relevelant snippet in the developer doc: hostname c.GitLabRepoProvider.hostname = Unicode('gitlab.com') The host of the GitLab instance The string `c.GitLabRepoProvider.hostname` here means, that the value of the `hostname` parameter will be loaded at the path config.GitLabRepoProvider inside a configuration file. Using the yaml synthax this means the configuration file should contain a snippet like: config: GitlabRepoProvider hostname: my-domain.com ### Digging through Kubernetes constructs: Helm values files When installing BinderHub using the provided helm chart, we can either put the configuration snippet in the config.yaml or secret.yaml helm values files. In my case I have put the snippet in config.yaml, since the hostname is not a secret thing, I can verify with **`yq`** that it correctly set: $ yq --raw-output '.config.GitLabRepoProvider.hostname' config.yaml my-domain.com How do we make sure this parameter is properly applied to our running binder processes ? As said previouly this parameter is passed as a value file to **`helm`** (–value or -f option) in the command: $ helm upgrade \ binderhub \ jupyterhub/binderhub \ --install \ --version=$(RELEASE) \ --create-namespace \ --namespace=binderhub \ --values secret.yaml \ --values config.yaml \ --debug According to the helm documentation in https://helm.sh/docs/helm/helm_install/ the values file are concatenated to form a single object, and priority will be given to the last (right-most) file specified. For example, if both myvalues.yaml and override.yaml contained a key called ‘Test’, the value set in override.yaml would take precedence: $ helm install --values myvalues.yaml --values override.yaml myredis ./redis ### Digging through Kubernetes constructs: Secrets and Volumes When `helm upgrade` is run the helm values of type `config` are stashed in a Kubernetes secret `binder-secret`: https://github.com/jupyterhub/binderhub/blob/main/helm-chart/binderhub/templates/secret.yaml#L12 stringData: {{- /* Stash away relevant Helm template values for the BinderHub Python application to read from in binderhub_config.py. */}} values.yaml: | {{- pick .Values "config" "imageBuilderType" "cors" "dind" "pink" "extraConfig" | toYaml | nindent 4 }} We can verify that our hostname is passed to our Secret: $ kubectl get secret binder-secret -o yaml | yq --raw-output '.data."values.yaml"' | base64 --decode ... GitLabRepoProvider: hostname: my-domain.com ... Finally a configuration file inside the Binder pod is populated from the Secret, using the Kubernetes Volume construct. Looking at the Pod, we do see a volume called `config`, created from the `binder-secret` Secret: $ kubectl get pod -l component=binder -o yaml | grep --context 4 binder-secret volumes: - name: config secret: defaultMode: 420 secretName: binder-secret That volume is mounted inside the pod at `/etc/binderhub/config`: volumeMounts: - mountPath: /etc/binderhub/config/ name: config readOnly: true ### Runtime verification Looking inside our pod we see our hostname value available in a file underneath the mount point: oc exec binder-74d9c7db95-qtp8r -- grep hostname /etc/binderhub/config/values.yaml hostname: my-domain.com

### Context: At $WORK I am doing a lot of datascience work around Jupyter Notebooks and their ecosystem. Right now I am setting BinderHub, which is a service to start a Jupyter Notebook from a git repo in your browser. For setting up BinderHub I am using the BinderHub helm chart, and I was wondering how configuration changes are propagated from the BinderHub helm chart to the process running in a Kubernetes Pod. After going through this I can say I am not right now a great fan of Helm, as it looks to me like an unnecessary, overengineered abstraction layer on top of Kubernetes manifests. Or maybe it is just that I don’t want to learn the golang templating synthax. I am looking forward to testing Kustomize as an alternative, but I havn’t had the chance yet. ### Starting from the list of config parameters available: Although many parameters are mentioned in the installer document, you have to go to the developer doc at https://binderhub.readthedocs.io/en/latest/reference/ref-index.html to get a whole overview. In my case I want to set the `hostname` parameter for the Gitlab Repoprovider. This is the relevelant snippet in the developer doc: hostname c.GitLabRepoProvider.hostname = Unicode('gitlab.com') The host of the GitLab instance The string `c.GitLabRepoProvider.hostname` here means, that the value of the `hostname` parameter will be loaded at the path config.GitLabRepoProvider inside a configuration file. Using the yaml synthax this means the configuration file should contain a snippet like: config: GitlabRepoProvider hostname: my-domain.com ### Digging through Kubernetes constructs: Helm values files When installing BinderHub using the provided helm chart, we can either put the configuration snippet in the config.yaml or secret.yaml helm values files. In my case I have put the snippet in config.yaml, since the hostname is not a secret thing, I can verify with **`yq`** that it correctly set: $ yq --raw-output '.config.GitLabRepoProvider.hostname' config.yaml my-domain.com How do we make sure this parameter is properly applied to our running binder processes ? As said previouly this parameter is passed as a value file to **`helm`** (–value or -f option) in the command: $ helm upgrade \ binderhub \ jupyterhub/binderhub \ --install \ --version=$(RELEASE) \ --create-namespace \ --namespace=binderhub \ --values secret.yaml \ --values config.yaml \ --debug According to the helm documentation in https://helm.sh/docs/helm/helm_install/ the values file are concatenated to form a single object, and priority will be given to the last (right-most) file specified. For example, if both myvalues.yaml and override.yaml contained a key called ‘Test’, the value set in override.yaml would take precedence: $ helm install --values myvalues.yaml --values override.yaml myredis ./redis ### Digging through Kubernetes constructs: Secrets and Volumes When `helm upgrade` is run the helm values of type `config` are stashed in a Kubernetes secret `binder-secret`: https://github.com/jupyterhub/binderhub/blob/main/helm-chart/binderhub/templates/secret.yaml#L12 stringData: {{- /* Stash away relevant Helm template values for the BinderHub Python application to read from in binderhub_config.py. */}} values.yaml: | {{- pick .Values "config" "imageBuilderType" "cors" "dind" "pink" "extraConfig" | toYaml | nindent 4 }} We can verify that our hostname is passed to our Secret: $ kubectl get secret binder-secret -o yaml | yq --raw-output '.data."values.yaml"' | base64 --decode ... GitLabRepoProvider: hostname: my-domain.com ... Finally a configuration file inside the Binder pod is populated from the Secret, using the Kubernetes Volume construct. Looking at the Pod, we do see a volume called `config`, created from the `binder-secret` Secret: $ kubectl get pod -l component=binder -o yaml | grep --context 4 binder-secret volumes: - name: config secret: defaultMode: 420 secretName: binder-secret That volume is mounted inside the pod at `/etc/binderhub/config`: volumeMounts: - mountPath: /etc/binderhub/config/ name: config readOnly: true ### Runtime verification Looking inside our pod we see our hostname value available in a file underneath the mount point: oc exec binder-74d9c7db95-qtp8r -- grep hostname /etc/binderhub/config/values.yaml hostname: my-domain.com

### Context: At $WORK I am doing a lot of datascience work around Jupyter Notebooks and their ecosystem. Right now I am setting BinderHub, which is a service to start a Jupyter Notebook from a git repo in your browser. For setting up BinderHub I am using the BinderHub helm chart, and I was wondering how configuration changes are propagated from the BinderHub helm chart to the process running in a Kubernetes Pod. After going through this I can say I am not right now a great fan of Helm, as it looks to me like an unnecessary, overengineered abstraction layer on top of Kubernetes manifests. Or maybe it is just that I don’t want to learn the golang templating synthax. I am looking forward to testing Kustomize as an alternative, but I havn’t had the chance yet. ### Starting from the list of config parameters available: Although many parameters are mentioned in the installer document, you have to go to the developer doc at https://binderhub.readthedocs.io/en/latest/reference/ref-index.html to get a whole overview. In my case I want to set the `hostname` parameter for the Gitlab Repoprovider. This is the relevelant snippet in the developer doc: hostname c.GitLabRepoProvider.hostname = Unicode('gitlab.com') The host of the GitLab instance The string `c.GitLabRepoProvider.hostname` here means, that the value of the `hostname` parameter will be loaded at the path config.GitLabRepoProvider inside a configuration file. Using the yaml synthax this means the configuration file should contain a snippet like: config: GitlabRepoProvider hostname: my-domain.com ### Digging through Kubernetes constructs: Helm values files When installing BinderHub using the provided helm chart, we can either put the configuration snippet in the config.yaml or secret.yaml helm values files. In my case I have put the snippet in config.yaml, since the hostname is not a secret thing, I can verify with **`yq`** that it correctly set: $ yq --raw-output '.config.GitLabRepoProvider.hostname' config.yaml my-domain.com How do we make sure this parameter is properly applied to our running binder processes ? As said previouly this parameter is passed as a value file to **`helm`** (–value or -f option) in the command: $ helm upgrade \ binderhub \ jupyterhub/binderhub \ --install \ --version=$(RELEASE) \ --create-namespace \ --namespace=binderhub \ --values secret.yaml \ --values config.yaml \ --debug According to the helm documentation in https://helm.sh/docs/helm/helm_install/ the values file are concatenated to form a single object, and priority will be given to the last (right-most) file specified. For example, if both myvalues.yaml and override.yaml contained a key called ‘Test’, the value set in override.yaml would take precedence: $ helm install --values myvalues.yaml --values override.yaml myredis ./redis ### Digging through Kubernetes constructs: Secrets and Volumes When `helm upgrade` is run the helm values of type `config` are stashed in a Kubernetes secret `binder-secret`: https://github.com/jupyterhub/binderhub/blob/main/helm-chart/binderhub/templates/secret.yaml#L12 stringData: {{- /* Stash away relevant Helm template values for the BinderHub Python application to read from in binderhub_config.py. */}} values.yaml: | {{- pick .Values "config" "imageBuilderType" "cors" "dind" "pink" "extraConfig" | toYaml | nindent 4 }} We can verify that our hostname is passed to our Secret: $ kubectl get secret binder-secret -o yaml | yq --raw-output '.data."values.yaml"' | base64 --decode ... GitLabRepoProvider: hostname: my-domain.com ... Finally a configuration file inside the Binder pod is populated from the Secret, using the Kubernetes Volume construct. Looking at the Pod, we do see a volume called `config`, created from the `binder-secret` Secret: $ kubectl get pod -l component=binder -o yaml | grep --context 4 binder-secret volumes: - name: config secret: defaultMode: 420 secretName: binder-secret That volume is mounted inside the pod at `/etc/binderhub/config`: volumeMounts: - mountPath: /etc/binderhub/config/ name: config readOnly: true ### Runtime verification Looking inside our pod we see our hostname value available in a file underneath the mount point: oc exec binder-74d9c7db95-qtp8r -- grep hostname /etc/binderhub/config/values.yaml hostname: my-domain.com

### Context: At $WORK I am doing a lot of datascience work around Jupyter Notebooks and their ecosystem. Right now I am setting BinderHub, which is a service to start a Jupyter Notebook from a git repo in your browser. For setting up BinderHub I am using the BinderHub helm chart, and I was wondering how configuration changes are propagated from the BinderHub helm chart to the process running in a Kubernetes Pod. After going through this I can say I am not right now a great fan of Helm, as it looks to me like an unnecessary, overengineered abstraction layer on top of Kubernetes manifests. Or maybe it is just that I don’t want to learn the golang templating synthax. I am looking forward to testing Kustomize as an alternative, but I havn’t had the chance yet. ### Starting from the list of config parameters available: Although many parameters are mentioned in the installer document, you have to go to the developer doc at https://binderhub.readthedocs.io/en/latest/reference/ref-index.html to get a whole overview. In my case I want to set the `hostname` parameter for the Gitlab Repoprovider. This is the relevelant snippet in the developer doc: hostname c.GitLabRepoProvider.hostname = Unicode('gitlab.com') The host of the GitLab instance The string `c.GitLabRepoProvider.hostname` here means, that the value of the `hostname` parameter will be loaded at the path config.GitLabRepoProvider inside a configuration file. Using the yaml synthax this means the configuration file should contain a snippet like: config: GitlabRepoProvider hostname: my-domain.com ### Digging through Kubernetes constructs: Helm values files When installing BinderHub using the provided helm chart, we can either put the configuration snippet in the config.yaml or secret.yaml helm values files. In my case I have put the snippet in config.yaml, since the hostname is not a secret thing, I can verify with **`yq`** that it correctly set: $ yq --raw-output '.config.GitLabRepoProvider.hostname' config.yaml my-domain.com How do we make sure this parameter is properly applied to our running binder processes ? As said previouly this parameter is passed as a value file to **`helm`** (–value or -f option) in the command: $ helm upgrade \ binderhub \ jupyterhub/binderhub \ --install \ --version=$(RELEASE) \ --create-namespace \ --namespace=binderhub \ --values secret.yaml \ --values config.yaml \ --debug According to the helm documentation in https://helm.sh/docs/helm/helm_install/ the values file are concatenated to form a single object, and priority will be given to the last (right-most) file specified. For example, if both myvalues.yaml and override.yaml contained a key called ‘Test’, the value set in override.yaml would take precedence: $ helm install --values myvalues.yaml --values override.yaml myredis ./redis ### Digging through Kubernetes constructs: Secrets and Volumes When `helm upgrade` is run the helm values of type `config` are stashed in a Kubernetes secret `binder-secret`: https://github.com/jupyterhub/binderhub/blob/main/helm-chart/binderhub/templates/secret.yaml#L12 stringData: {{- /* Stash away relevant Helm template values for the BinderHub Python application to read from in binderhub_config.py. */}} values.yaml: | {{- pick .Values "config" "imageBuilderType" "cors" "dind" "pink" "extraConfig" | toYaml | nindent 4 }} We can verify that our hostname is passed to our Secret: $ kubectl get secret binder-secret -o yaml | yq --raw-output '.data."values.yaml"' | base64 --decode ... GitLabRepoProvider: hostname: my-domain.com ... Finally a configuration file inside the Binder pod is populated from the Secret, using the Kubernetes Volume construct. Looking at the Pod, we do see a volume called `config`, created from the `binder-secret` Secret: $ kubectl get pod -l component=binder -o yaml | grep --context 4 binder-secret volumes: - name: config secret: defaultMode: 420 secretName: binder-secret That volume is mounted inside the pod at `/etc/binderhub/config`: volumeMounts: - mountPath: /etc/binderhub/config/ name: config readOnly: true ### Runtime verification Looking inside our pod we see our hostname value available in a file underneath the mount point: oc exec binder-74d9c7db95-qtp8r -- grep hostname /etc/binderhub/config/values.yaml hostname: my-domain.com

### Context: At $WORK I am doing a lot of datascience work around Jupyter Notebooks and their ecosystem. Right now I am setting BinderHub, which is a service to start a Jupyter Notebook from a git repo in your browser. For setting up BinderHub I am using the BinderHub helm chart, and I was wondering how configuration changes are propagated from the BinderHub helm chart to the process running in a Kubernetes Pod. After going through this I can say I am not right now a great fan of Helm, as it looks to me like an unnecessary, overengineered abstraction layer on top of Kubernetes manifests. Or maybe it is just that I don’t want to learn the golang templating synthax. I am looking forward to testing Kustomize as an alternative, but I havn’t had the chance yet. ### Starting from the list of config parameters available: Although many parameters are mentioned in the installer document, you have to go to the developer doc at https://binderhub.readthedocs.io/en/latest/reference/ref-index.html to get a whole overview. In my case I want to set the `hostname` parameter for the Gitlab Repoprovider. This is the relevelant snippet in the developer doc: hostname c.GitLabRepoProvider.hostname = Unicode('gitlab.com') The host of the GitLab instance The string `c.GitLabRepoProvider.hostname` here means, that the value of the `hostname` parameter will be loaded at the path config.GitLabRepoProvider inside a configuration file. Using the yaml synthax this means the configuration file should contain a snippet like: config: GitlabRepoProvider hostname: my-domain.com ### Digging through Kubernetes constructs: Helm values files When installing BinderHub using the provided helm chart, we can either put the configuration snippet in the config.yaml or secret.yaml helm values files. In my case I have put the snippet in config.yaml, since the hostname is not a secret thing, I can verify with **`yq`** that it correctly set: $ yq --raw-output '.config.GitLabRepoProvider.hostname' config.yaml my-domain.com How do we make sure this parameter is properly applied to our running binder processes ? As said previouly this parameter is passed as a value file to **`helm`** (–value or -f option) in the command: $ helm upgrade \ binderhub \ jupyterhub/binderhub \ --install \ --version=$(RELEASE) \ --create-namespace \ --namespace=binderhub \ --values secret.yaml \ --values config.yaml \ --debug According to the helm documentation in https://helm.sh/docs/helm/helm_install/ the values file are concatenated to form a single object, and priority will be given to the last (right-most) file specified. For example, if both myvalues.yaml and override.yaml contained a key called ‘Test’, the value set in override.yaml would take precedence: $ helm install --values myvalues.yaml --values override.yaml myredis ./redis ### Digging through Kubernetes constructs: Secrets and Volumes When `helm upgrade` is run the helm values of type `config` are stashed in a Kubernetes secret `binder-secret`: https://github.com/jupyterhub/binderhub/blob/main/helm-chart/binderhub/templates/secret.yaml#L12 stringData: {{- /* Stash away relevant Helm template values for the BinderHub Python application to read from in binderhub_config.py. */}} values.yaml: | {{- pick .Values "config" "imageBuilderType" "cors" "dind" "pink" "extraConfig" | toYaml | nindent 4 }} We can verify that our hostname is passed to our Secret: $ kubectl get secret binder-secret -o yaml | yq --raw-output '.data."values.yaml"' | base64 --decode ... GitLabRepoProvider: hostname: my-domain.com ... Finally a configuration file inside the Binder pod is populated from the Secret, using the Kubernetes Volume construct. Looking at the Pod, we do see a volume called `config`, created from the `binder-secret` Secret: $ kubectl get pod -l component=binder -o yaml | grep --context 4 binder-secret volumes: - name: config secret: defaultMode: 420 secretName: binder-secret That volume is mounted inside the pod at `/etc/binderhub/config`: volumeMounts: - mountPath: /etc/binderhub/config/ name: config readOnly: true ### Runtime verification Looking inside our pod we see our hostname value available in a file underneath the mount point: oc exec binder-74d9c7db95-qtp8r -- grep hostname /etc/binderhub/config/values.yaml hostname: my-domain.com

### Context: At $WORK I am doing a lot of datascience work around Jupyter Notebooks and their ecosystem. Right now I am setting BinderHub, which is a service to start a Jupyter Notebook from a git repo in your browser. For setting up BinderHub I am using the BinderHub helm chart, and I was wondering how configuration changes are propagated from the BinderHub helm chart to the process running in a Kubernetes Pod. After going through this I can say I am not right now a great fan of Helm, as it looks to me like an unnecessary, overengineered abstraction layer on top of Kubernetes manifests. Or maybe it is just that I don’t want to learn the golang templating synthax. I am looking forward to testing Kustomize as an alternative, but I havn’t had the chance yet. ### Starting from the list of config parameters available: Although many parameters are mentioned in the installer document, you have to go to the developer doc at https://binderhub.readthedocs.io/en/latest/reference/ref-index.html to get a whole overview. In my case I want to set the `hostname` parameter for the Gitlab Repoprovider. This is the relevelant snippet in the developer doc: hostname c.GitLabRepoProvider.hostname = Unicode('gitlab.com') The host of the GitLab instance The string `c.GitLabRepoProvider.hostname` here means, that the value of the `hostname` parameter will be loaded at the path config.GitLabRepoProvider inside a configuration file. Using the yaml synthax this means the configuration file should contain a snippet like: config: GitlabRepoProvider hostname: my-domain.com ### Digging through Kubernetes constructs: Helm values files When installing BinderHub using the provided helm chart, we can either put the configuration snippet in the config.yaml or secret.yaml helm values files. In my case I have put the snippet in config.yaml, since the hostname is not a secret thing, I can verify with **`yq`** that it correctly set: $ yq --raw-output '.config.GitLabRepoProvider.hostname' config.yaml my-domain.com How do we make sure this parameter is properly applied to our running binder processes ? As said previouly this parameter is passed as a value file to **`helm`** (–value or -f option) in the command: $ helm upgrade \ binderhub \ jupyterhub/binderhub \ --install \ --version=$(RELEASE) \ --create-namespace \ --namespace=binderhub \ --values secret.yaml \ --values config.yaml \ --debug According to the helm documentation in https://helm.sh/docs/helm/helm_install/ the values file are concatenated to form a single object, and priority will be given to the last (right-most) file specified. For example, if both myvalues.yaml and override.yaml contained a key called ‘Test’, the value set in override.yaml would take precedence: $ helm install --values myvalues.yaml --values override.yaml myredis ./redis ### Digging through Kubernetes constructs: Secrets and Volumes When `helm upgrade` is run the helm values of type `config` are stashed in a Kubernetes secret `binder-secret`: https://github.com/jupyterhub/binderhub/blob/main/helm-chart/binderhub/templates/secret.yaml#L12 stringData: {{- /* Stash away relevant Helm template values for the BinderHub Python application to read from in binderhub_config.py. */}} values.yaml: | {{- pick .Values "config" "imageBuilderType" "cors" "dind" "pink" "extraConfig" | toYaml | nindent 4 }} We can verify that our hostname is passed to our Secret: $ kubectl get secret binder-secret -o yaml | yq --raw-output '.data."values.yaml"' | base64 --decode ... GitLabRepoProvider: hostname: my-domain.com ... Finally a configuration file inside the Binder pod is populated from the Secret, using the Kubernetes Volume construct. Looking at the Pod, we do see a volume called `config`, created from the `binder-secret` Secret: $ kubectl get pod -l component=binder -o yaml | grep --context 4 binder-secret volumes: - name: config secret: defaultMode: 420 secretName: binder-secret That volume is mounted inside the pod at `/etc/binderhub/config`: volumeMounts: - mountPath: /etc/binderhub/config/ name: config readOnly: true ### Runtime verification Looking inside our pod we see our hostname value available in a file underneath the mount point: oc exec binder-74d9c7db95-qtp8r -- grep hostname /etc/binderhub/config/values.yaml hostname: my-domain.com

### Context: At $WORK I am doing a lot of datascience work around Jupyter Notebooks and their ecosystem. Right now I am setting BinderHub, which is a service to start a Jupyter Notebook from a git repo in your browser. For setting up BinderHub I am using the BinderHub helm chart, and I was wondering how configuration changes are propagated from the BinderHub helm chart to the process running in a Kubernetes Pod. After going through this I can say I am not right now a great fan of Helm, as it looks to me like an unnecessary, overengineered abstraction layer on top of Kubernetes manifests. Or maybe it is just that I don’t want to learn the golang templating synthax. I am looking forward to testing Kustomize as an alternative, but I havn’t had the chance yet. ### Starting from the list of config parameters available: Although many parameters are mentioned in the installer document, you have to go to the developer doc at https://binderhub.readthedocs.io/en/latest/reference/ref-index.html to get a whole overview. In my case I want to set the `hostname` parameter for the Gitlab Repoprovider. This is the relevelant snippet in the developer doc: hostname c.GitLabRepoProvider.hostname = Unicode('gitlab.com') The host of the GitLab instance The string `c.GitLabRepoProvider.hostname` here means, that the value of the `hostname` parameter will be loaded at the path config.GitLabRepoProvider inside a configuration file. Using the yaml synthax this means the configuration file should contain a snippet like: config: GitlabRepoProvider hostname: my-domain.com ### Digging through Kubernetes constructs: Helm values files When installing BinderHub using the provided helm chart, we can either put the configuration snippet in the config.yaml or secret.yaml helm values files. In my case I have put the snippet in config.yaml, since the hostname is not a secret thing, I can verify with **`yq`** that it correctly set: $ yq --raw-output '.config.GitLabRepoProvider.hostname' config.yaml my-domain.com How do we make sure this parameter is properly applied to our running binder processes ? As said previouly this parameter is passed as a value file to **`helm`** (–value or -f option) in the command: $ helm upgrade \ binderhub \ jupyterhub/binderhub \ --install \ --version=$(RELEASE) \ --create-namespace \ --namespace=binderhub \ --values secret.yaml \ --values config.yaml \ --debug According to the helm documentation in https://helm.sh/docs/helm/helm_install/ the values file are concatenated to form a single object, and priority will be given to the last (right-most) file specified. For example, if both myvalues.yaml and override.yaml contained a key called ‘Test’, the value set in override.yaml would take precedence: $ helm install --values myvalues.yaml --values override.yaml myredis ./redis ### Digging through Kubernetes constructs: Secrets and Volumes When `helm upgrade` is run the helm values of type `config` are stashed in a Kubernetes secret `binder-secret`: https://github.com/jupyterhub/binderhub/blob/main/helm-chart/binderhub/templates/secret.yaml#L12 stringData: {{- /* Stash away relevant Helm template values for the BinderHub Python application to read from in binderhub_config.py. */}} values.yaml: | {{- pick .Values "config" "imageBuilderType" "cors" "dind" "pink" "extraConfig" | toYaml | nindent 4 }} We can verify that our hostname is passed to our Secret: $ kubectl get secret binder-secret -o yaml | yq --raw-output '.data."values.yaml"' | base64 --decode ... GitLabRepoProvider: hostname: my-domain.com ... Finally a configuration file inside the Binder pod is populated from the Secret, using the Kubernetes Volume construct. Looking at the Pod, we do see a volume called `config`, created from the `binder-secret` Secret: $ kubectl get pod -l component=binder -o yaml | grep --context 4 binder-secret volumes: - name: config secret: defaultMode: 420 secretName: binder-secret That volume is mounted inside the pod at `/etc/binderhub/config`: volumeMounts: - mountPath: /etc/binderhub/config/ name: config readOnly: true ### Runtime verification Looking inside our pod we see our hostname value available in a file underneath the mount point: oc exec binder-74d9c7db95-qtp8r -- grep hostname /etc/binderhub/config/values.yaml hostname: my-domain.com

### Context: At $WORK I am doing a lot of datascience work around Jupyter Notebooks and their ecosystem. Right now I am setting BinderHub, which is a service to start a Jupyter Notebook from a git repo in your browser. For setting up BinderHub I am using the BinderHub helm chart, and I was wondering how configuration changes are propagated from the BinderHub helm chart to the process running in a Kubernetes Pod. After going through this I can say I am not right now a great fan of Helm, as it looks to me like an unnecessary, overengineered abstraction layer on top of Kubernetes manifests. Or maybe it is just that I don’t want to learn the golang templating synthax. I am looking forward to testing Kustomize as an alternative, but I havn’t had the chance yet. ### Starting from the list of config parameters available: Although many parameters are mentioned in the installer document, you have to go to the developer doc at https://binderhub.readthedocs.io/en/latest/reference/ref-index.html to get a whole overview. In my case I want to set the `hostname` parameter for the Gitlab Repoprovider. This is the relevelant snippet in the developer doc: hostname c.GitLabRepoProvider.hostname = Unicode('gitlab.com') The host of the GitLab instance The string `c.GitLabRepoProvider.hostname` here means, that the value of the `hostname` parameter will be loaded at the path config.GitLabRepoProvider inside a configuration file. Using the yaml synthax this means the configuration file should contain a snippet like: config: GitlabRepoProvider hostname: my-domain.com ### Digging through Kubernetes constructs: Helm values files When installing BinderHub using the provided helm chart, we can either put the configuration snippet in the config.yaml or secret.yaml helm values files. In my case I have put the snippet in config.yaml, since the hostname is not a secret thing, I can verify with **`yq`** that it correctly set: $ yq --raw-output '.config.GitLabRepoProvider.hostname' config.yaml my-domain.com How do we make sure this parameter is properly applied to our running binder processes ? As said previouly this parameter is passed as a value file to **`helm`** (–value or -f option) in the command: $ helm upgrade \ binderhub \ jupyterhub/binderhub \ --install \ --version=$(RELEASE) \ --create-namespace \ --namespace=binderhub \ --values secret.yaml \ --values config.yaml \ --debug According to the helm documentation in https://helm.sh/docs/helm/helm_install/ the values file are concatenated to form a single object, and priority will be given to the last (right-most) file specified. For example, if both myvalues.yaml and override.yaml contained a key called ‘Test’, the value set in override.yaml would take precedence: $ helm install --values myvalues.yaml --values override.yaml myredis ./redis ### Digging through Kubernetes constructs: Secrets and Volumes When `helm upgrade` is run the helm values of type `config` are stashed in a Kubernetes secret `binder-secret`: https://github.com/jupyterhub/binderhub/blob/main/helm-chart/binderhub/templates/secret.yaml#L12 stringData: {{- /* Stash away relevant Helm template values for the BinderHub Python application to read from in binderhub_config.py. */}} values.yaml: | {{- pick .Values "config" "imageBuilderType" "cors" "dind" "pink" "extraConfig" | toYaml | nindent 4 }} We can verify that our hostname is passed to our Secret: $ kubectl get secret binder-secret -o yaml | yq --raw-output '.data."values.yaml"' | base64 --decode ... GitLabRepoProvider: hostname: my-domain.com ... Finally a configuration file inside the Binder pod is populated from the Secret, using the Kubernetes Volume construct. Looking at the Pod, we do see a volume called `config`, created from the `binder-secret` Secret: $ kubectl get pod -l component=binder -o yaml | grep --context 4 binder-secret volumes: - name: config secret: defaultMode: 420 secretName: binder-secret That volume is mounted inside the pod at `/etc/binderhub/config`: volumeMounts: - mountPath: /etc/binderhub/config/ name: config readOnly: true ### Runtime verification Looking inside our pod we see our hostname value available in a file underneath the mount point: oc exec binder-74d9c7db95-qtp8r -- grep hostname /etc/binderhub/config/values.yaml hostname: my-domain.com

### Context: At $WORK I am doing a lot of datascience work around Jupyter Notebooks and their ecosystem. Right now I am setting BinderHub, which is a service to start a Jupyter Notebook from a git repo in your browser. For setting up BinderHub I am using the BinderHub helm chart, and I was wondering how configuration changes are propagated from the BinderHub helm chart to the process running in a Kubernetes Pod. After going through this I can say I am not right now a great fan of Helm, as it looks to me like an unnecessary, overengineered abstraction layer on top of Kubernetes manifests. Or maybe it is just that I don’t want to learn the golang templating synthax. I am looking forward to testing Kustomize as an alternative, but I havn’t had the chance yet. ### Starting from the list of config parameters available: Although many parameters are mentioned in the installer document, you have to go to the developer doc at https://binderhub.readthedocs.io/en/latest/reference/ref-index.html to get a whole overview. In my case I want to set the `hostname` parameter for the Gitlab Repoprovider. This is the relevelant snippet in the developer doc: hostname c.GitLabRepoProvider.hostname = Unicode('gitlab.com') The host of the GitLab instance The string `c.GitLabRepoProvider.hostname` here means, that the value of the `hostname` parameter will be loaded at the path config.GitLabRepoProvider inside a configuration file. Using the yaml synthax this means the configuration file should contain a snippet like: config: GitlabRepoProvider hostname: my-domain.com ### Digging through Kubernetes constructs: Helm values files When installing BinderHub using the provided helm chart, we can either put the configuration snippet in the config.yaml or secret.yaml helm values files. In my case I have put the snippet in config.yaml, since the hostname is not a secret thing, I can verify with **`yq`** that it correctly set: $ yq --raw-output '.config.GitLabRepoProvider.hostname' config.yaml my-domain.com How do we make sure this parameter is properly applied to our running binder processes ? As said previouly this parameter is passed as a value file to **`helm`** (–value or -f option) in the command: $ helm upgrade \ binderhub \ jupyterhub/binderhub \ --install \ --version=$(RELEASE) \ --create-namespace \ --namespace=binderhub \ --values secret.yaml \ --values config.yaml \ --debug According to the helm documentation in https://helm.sh/docs/helm/helm_install/ the values file are concatenated to form a single object, and priority will be given to the last (right-most) file specified. For example, if both myvalues.yaml and override.yaml contained a key called ‘Test’, the value set in override.yaml would take precedence: $ helm install --values myvalues.yaml --values override.yaml myredis ./redis ### Digging through Kubernetes constructs: Secrets and Volumes When `helm upgrade` is run the helm values of type `config` are stashed in a Kubernetes secret `binder-secret`: https://github.com/jupyterhub/binderhub/blob/main/helm-chart/binderhub/templates/secret.yaml#L12 stringData: {{- /* Stash away relevant Helm template values for the BinderHub Python application to read from in binderhub_config.py. */}} values.yaml: | {{- pick .Values "config" "imageBuilderType" "cors" "dind" "pink" "extraConfig" | toYaml | nindent 4 }} We can verify that our hostname is passed to our Secret: $ kubectl get secret binder-secret -o yaml | yq --raw-output '.data."values.yaml"' | base64 --decode ... GitLabRepoProvider: hostname: my-domain.com ... Finally a configuration file inside the Binder pod is populated from the Secret, using the Kubernetes Volume construct. Looking at the Pod, we do see a volume called `config`, created from the `binder-secret` Secret: $ kubectl get pod -l component=binder -o yaml | grep --context 4 binder-secret volumes: - name: config secret: defaultMode: 420 secretName: binder-secret That volume is mounted inside the pod at `/etc/binderhub/config`: volumeMounts: - mountPath: /etc/binderhub/config/ name: config readOnly: true ### Runtime verification Looking inside our pod we see our hostname value available in a file underneath the mount point: oc exec binder-74d9c7db95-qtp8r -- grep hostname /etc/binderhub/config/values.yaml hostname: my-domain.com

### Context: At $WORK I am doing a lot of datascience work around Jupyter Notebooks and their ecosystem. Right now I am setting BinderHub, which is a service to start a Jupyter Notebook from a git repo in your browser. For setting up BinderHub I am using the BinderHub helm chart, and I was wondering how configuration changes are propagated from the BinderHub helm chart to the process running in a Kubernetes Pod. After going through this I can say I am not right now a great fan of Helm, as it looks to me like an unnecessary, overengineered abstraction layer on top of Kubernetes manifests. Or maybe it is just that I don’t want to learn the golang templating synthax. I am looking forward to testing Kustomize as an alternative, but I havn’t had the chance yet. ### Starting from the list of config parameters available: Although many parameters are mentioned in the installer document, you have to go to the developer doc at https://binderhub.readthedocs.io/en/latest/reference/ref-index.html to get a whole overview. In my case I want to set the `hostname` parameter for the Gitlab Repoprovider. This is the relevelant snippet in the developer doc: hostname c.GitLabRepoProvider.hostname = Unicode('gitlab.com') The host of the GitLab instance The string `c.GitLabRepoProvider.hostname` here means, that the value of the `hostname` parameter will be loaded at the path config.GitLabRepoProvider inside a configuration file. Using the yaml synthax this means the configuration file should contain a snippet like: config: GitlabRepoProvider hostname: my-domain.com ### Digging through Kubernetes constructs: Helm values files When installing BinderHub using the provided helm chart, we can either put the configuration snippet in the config.yaml or secret.yaml helm values files. In my case I have put the snippet in config.yaml, since the hostname is not a secret thing, I can verify with **`yq`** that it correctly set: $ yq --raw-output '.config.GitLabRepoProvider.hostname' config.yaml my-domain.com How do we make sure this parameter is properly applied to our running binder processes ? As said previouly this parameter is passed as a value file to **`helm`** (–value or -f option) in the command: $ helm upgrade \ binderhub \ jupyterhub/binderhub \ --install \ --version=$(RELEASE) \ --create-namespace \ --namespace=binderhub \ --values secret.yaml \ --values config.yaml \ --debug According to the helm documentation in https://helm.sh/docs/helm/helm_install/ the values file are concatenated to form a single object, and priority will be given to the last (right-most) file specified. For example, if both myvalues.yaml and override.yaml contained a key called ‘Test’, the value set in override.yaml would take precedence: $ helm install --values myvalues.yaml --values override.yaml myredis ./redis ### Digging through Kubernetes constructs: Secrets and Volumes When `helm upgrade` is run the helm values of type `config` are stashed in a Kubernetes secret `binder-secret`: https://github.com/jupyterhub/binderhub/blob/main/helm-chart/binderhub/templates/secret.yaml#L12 stringData: {{- /* Stash away relevant Helm template values for the BinderHub Python application to read from in binderhub_config.py. */}} values.yaml: | {{- pick .Values "config" "imageBuilderType" "cors" "dind" "pink" "extraConfig" | toYaml | nindent 4 }} We can verify that our hostname is passed to our Secret: $ kubectl get secret binder-secret -o yaml | yq --raw-output '.data."values.yaml"' | base64 --decode ... GitLabRepoProvider: hostname: my-domain.com ... Finally a configuration file inside the Binder pod is populated from the Secret, using the Kubernetes Volume construct. Looking at the Pod, we do see a volume called `config`, created from the `binder-secret` Secret: $ kubectl get pod -l component=binder -o yaml | grep --context 4 binder-secret volumes: - name: config secret: defaultMode: 420 secretName: binder-secret That volume is mounted inside the pod at `/etc/binderhub/config`: volumeMounts: - mountPath: /etc/binderhub/config/ name: config readOnly: true ### Runtime verification Looking inside our pod we see our hostname value available in a file underneath the mount point: oc exec binder-74d9c7db95-qtp8r -- grep hostname /etc/binderhub/config/values.yaml hostname: my-domain.com

### Context: At $WORK I am doing a lot of datascience work around Jupyter Notebooks and their ecosystem. Right now I am setting BinderHub, which is a service to start a Jupyter Notebook from a git repo in your browser. For setting up BinderHub I am using the BinderHub helm chart, and I was wondering how configuration changes are propagated from the BinderHub helm chart to the process running in a Kubernetes Pod. After going through this I can say I am not right now a great fan of Helm, as it looks to me like an unnecessary, overengineered abstraction layer on top of Kubernetes manifests. Or maybe it is just that I don’t want to learn the golang templating synthax. I am looking forward to testing Kustomize as an alternative, but I havn’t had the chance yet. ### Starting from the list of config parameters available: Although many parameters are mentioned in the installer document, you have to go to the developer doc at https://binderhub.readthedocs.io/en/latest/reference/ref-index.html to get a whole overview. In my case I want to set the `hostname` parameter for the Gitlab Repoprovider. This is the relevelant snippet in the developer doc: hostname c.GitLabRepoProvider.hostname = Unicode('gitlab.com') The host of the GitLab instance The string `c.GitLabRepoProvider.hostname` here means, that the value of the `hostname` parameter will be loaded at the path config.GitLabRepoProvider inside a configuration file. Using the yaml synthax this means the configuration file should contain a snippet like: config: GitlabRepoProvider hostname: my-domain.com ### Digging through Kubernetes constructs: Helm values files When installing BinderHub using the provided helm chart, we can either put the configuration snippet in the config.yaml or secret.yaml helm values files. In my case I have put the snippet in config.yaml, since the hostname is not a secret thing, I can verify with **`yq`** that it correctly set: $ yq --raw-output '.config.GitLabRepoProvider.hostname' config.yaml my-domain.com How do we make sure this parameter is properly applied to our running binder processes ? As said previouly this parameter is passed as a value file to **`helm`** (–value or -f option) in the command: $ helm upgrade \ binderhub \ jupyterhub/binderhub \ --install \ --version=$(RELEASE) \ --create-namespace \ --namespace=binderhub \ --values secret.yaml \ --values config.yaml \ --debug According to the helm documentation in https://helm.sh/docs/helm/helm_install/ the values file are concatenated to form a single object, and priority will be given to the last (right-most) file specified. For example, if both myvalues.yaml and override.yaml contained a key called ‘Test’, the value set in override.yaml would take precedence: $ helm install --values myvalues.yaml --values override.yaml myredis ./redis ### Digging through Kubernetes constructs: Secrets and Volumes When `helm upgrade` is run the helm values of type `config` are stashed in a Kubernetes secret `binder-secret`: https://github.com/jupyterhub/binderhub/blob/main/helm-chart/binderhub/templates/secret.yaml#L12 stringData: {{- /* Stash away relevant Helm template values for the BinderHub Python application to read from in binderhub_config.py. */}} values.yaml: | {{- pick .Values "config" "imageBuilderType" "cors" "dind" "pink" "extraConfig" | toYaml | nindent 4 }} We can verify that our hostname is passed to our Secret: $ kubectl get secret binder-secret -o yaml | yq --raw-output '.data."values.yaml"' | base64 --decode ... GitLabRepoProvider: hostname: my-domain.com ... Finally a configuration file inside the Binder pod is populated from the Secret, using the Kubernetes Volume construct. Looking at the Pod, we do see a volume called `config`, created from the `binder-secret` Secret: $ kubectl get pod -l component=binder -o yaml | grep --context 4 binder-secret volumes: - name: config secret: defaultMode: 420 secretName: binder-secret That volume is mounted inside the pod at `/etc/binderhub/config`: volumeMounts: - mountPath: /etc/binderhub/config/ name: config readOnly: true ### Runtime verification Looking inside our pod we see our hostname value available in a file underneath the mount point: oc exec binder-74d9c7db95-qtp8r -- grep hostname /etc/binderhub/config/values.yaml hostname: my-domain.com