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Add your namespaces with HNS

info

Feature available with Babel 2.1+

Manage your namespaces​

Customer's namespaces are managed with the concept of Hierarchical Namespaces. In its simplest form, a hierarchical namespace is a regular Kubernetes namespace that contains a small custom resource that identifies a single, optional, parent namespace. This establishes the concept of ownership across namespaces, not just within them. This concept of ownership enables the policy inheritance: if one namespace is a child of another, policy objects such as RBAC RoleBindings are copied from the parent to the child.

The cluster service owner has permission to create namespace under its own namespaces such as customer-namespaces in your case. The created namespaces wil have the exact same permission has the parent namespace.

Example of customer namespace structure

customer-namespaces
├── namespace-a
├── namespace-b
└── ...

Setup tools​

Install hns kubectl plugin

  1. Install krew macOS/Linux (Bash or ZSH shells). Reference

    1. Make sure that git is installed.
    2. Run this command to download and install krew: 
      (
      set -x; cd "$(mktemp -d)" &&
      OS="$(uname | tr '[:upper:]' '[:lower:]')" &&
      ARCH="$(uname -m | sed -e 's/x86_64/amd64/' -e 's/\(arm\)\(64\)\?.*/\1\2/' -e 's/aarch64$/arm64/')" &&
      KREW="krew-${OS}_${ARCH}" &&
      curl -fsSLO "https://github.com/kubernetes-sigs/krew/releases/latest/download/${KREW}.tar.gz" &&
      tar zxvf "${KREW}.tar.gz" &&
      ./"${KREW}" install krew
      )
    3. Add the $HOME/.krew/bin directory to your PATH environment variable. To do this, update your .bashrc or .zshrc file and append the following line: export PATH="${KREW_ROOT:-$HOME/.krew}/bin:$PATH" and restart your shell.
    4. Run kubectl krew to check the installation

  2. Install hns plugin with krew

    kubectl krew update && kubectl krew install hns

  3. Test installation

    kubectl hns

    Output:

    Manipulates hierarchical namespaces provided by HNC

    Usage:
    kubectl-hns [command]

    Available Commands:
    completion  generate the autocompletion script for the specified shell
    [...]

Manage your namespaces​

  • Create namespace

    kubectl hns create <my-new-namespace> -n customer-namespaces

  • List namespaces

    kubectl get ns

    Output:

    cert-manager                Active   6d
    default                     Active   6d1h
    [...]

    Note: All cluster namespaces. No distinction between regular namespace and hierarchical namespace

  • Show namespace structure

    kubectl hns tree customer-namespaces

    Output:

    customer-namespaces
    ├── namespace-a
    ├── namespace-b
    └── ...

  • Detail namespace

    kubectl describe ns <my-new-namespace>

    Output:

    Name:         my-new-namespace
    Labels:       customer-namespaces.tree.hnc.x-k8s.io/depth=1
                hnc.x-k8s.io/included-namespace=true
                kubernetes.io/metadata.name=my-new-namespace
                my-new-namespace.tree.hnc.x-k8s.io/depth=0
    Annotations:  hnc.x-k8s.io/subnamespace-of: customer-namespaces
    Status:       Active

    No resource quota.

    No LimitRange resource.

    Note: Labels and annotations contain information about the parent's namespace.

  • Delete namespace

    kubectl delete subnamespaceanchor <my-namespace-to-delete> -n customer-namespaces

    Output:

    subnamespaceanchor.hnc.x-k8s.io "my-sub-namespace" deleted

Work with namespace​

Use service account​

For any subnamespaces of customer-namespaces or customer-namespaces use customer-namespaces

  1. Download kubeconfig script
  2. Set k8saas-service-account-kubeconfig.sh executable
  3. Retrieve customer-namespaces kubeconfig 
    k8saas-service-account-kubeconfig.sh customer-namespaces
  4. Do your operations on customer-namespaces or its child Some examples 
    kubectl get secret -n customer-namespaces --kubeconfig <customer-namespaces-sa-kubeconfig-file>
    kubectl get pod -n customer-namespaces-child --kubeconfig <customer-namespaces-sa-kubeconfig-file>
    ...

Known limitations and troubleshooting​

Service account permission issue while using child SA in child namespace​

Current HNC version propagates SA from parent to child namespace however the secret associated to the SA is not propagated. Using the child SA for operations on cluster returns permission errors.

The workaround is to use the parent SA for all operations on sub-child. Using the parent SA for its child isn't a security concern because HNC is based on the assumption that if you have access to the parent, it's normal to have access to its childs.

In case where you are deploying in a customer-namespaces child a pod using SA permission, the SA in customer-namespaces(parent) is not accessible. Error creating: pods "..." is forbidden: error looking up service account <customer-namespaces child>/k8saas-generic-sa-cicd: serviceaccount "k8saas-generic-sa-cicd" not found

The solution is to create a new SA in the customer-namespaces child and use this new SA inside the deployed pod. Retrieve new SA kubeconfig

k8saas-service-account-kubeconfig.sh <service-account-namespace> <service-account-name>