Update cluster class to install NFS client on Ubuntu 22.04 and TKGm 2.5.1
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Update cluster class to install NFS client on Ubuntu 22.04 and TKGm 2.5.1

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Article ID: 376737

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Updated On:

Products

VMware Tanzu Kubernetes Grid Plus

Issue/Introduction

After upgrade of Ubuntu based classy clusters to 22.04 TKGm 2.5.1 the NFS client is no longer available (installed by default).

kubectl describe node $NODE
#> MountVolume.SetUp failed for volume "######" : mount failed: exit status 32 Mounting command: mount Mounting arguments: -t nfs #####:/#####/ /var/lib/kubelet/pods/####/volumes/kubernetes.io~nfs/#### Output: mount: /var/lib/kubelet/pods/####/volumes/kubernetes.io~nfs/####: bad option; for several filesystems (e.g. nfs, cifs) you might need a /sbin/mount.<type> helper program.

Environment

  • TKGm 2.5.1
  • TKGm 2.5.x

Cause

NFS client  packages were removed on 2.5.1 due to the NFS usage of RPCbind (which is bound on port 111 by default);  it was disabled to comply with the Ubuntu CIS Benchmark C-2.3.6.

TKGm does not support external NFS, and so far, there have been no reports of usage. NFS is only supported in the datastore via CSI.

Installing it back will regress a security issue and is out of the scope.
There are two alternatives to toggle the hardening procedures:

1) Bring Your Own Image, change the variables passed (adding these packages), and export a new template that can be used - this is more complex procedure and is not covered with this article 
2) Create a custom ClusterClass, to install the package before the node joins the cluster (preKubeadmCommand) - Procedure below

Resolution

Prerequisites

TKGm management cluster is created (tested with 2.5)
ytt installed
kubectl installed and set to management cluster context
Tanzu CLI

This process involves creating a custom cluster class that allows for deploying worker nodes in a workload cluster with NFS common utils installed. Creating custom clusterclasses is roughly documented here.

  1. In Tanzu Kubernetes Grid 2.3.0 and later, after you deploy a management cluster, you can find the default ClusterClass manifest in the ~/.config/tanzu/tkg/clusterclassconfigs folder.
    • cp ~/.config/tanzu/tkg/clusterclassconfigs/tkg-vsphere-default-v1.2.0.yaml .
  2. To customize your ClusterClass manifest, you create ytt overlay files alongside the manifest. 
    • mkdir overlays
cd overlays

Return to top folder after creating the files: cd ..
Create a file nfscommon.yaml:
#@ load("@ytt:overlay", "overlay")

#@overlay/match by=overlay.subset({"kind":"ClusterClass"})
---
apiVersion: cluster.x-k8s.io/v1beta1
kind: ClusterClass
metadata:
  name: tkg-vsphere-default-v1.2.0-extended
spec:
  #@overlay/match missing_ok=True
  variables:
  #@overlay/append
  - name: nfsCommon
    required: false
    schema:
      openAPIV3Schema:
        type: boolean
        default: false
  #@overlay/match expects=1
  patches:
  #@overlay/append
  - name: nfs
    enabledIf: '{{ .nfsCommon }}'
    definitions:
      - selector:
          apiVersion: bootstrap.cluster.x-k8s.io/v1beta1
          kind: KubeadmConfigTemplate
          matchResources:
            machineDeploymentClass:
              names:
                - tkg-worker
        jsonPatches:
          - op: add
            path: /spec/template/spec/preKubeadmCommands/-
            value: |
              sudo add-apt-repository -s https://mirrors.bloomu.edu/ubuntu/ jammy main [mirrors.bloomu.edu] -y && \
              sudo apt update -y && \
              sudo apt-get install -y libnfsidmap1=1:2.6.1-1ubuntu1 --allow-downgrades --allow-change-held-packages && \
              sudo apt-get install -y nfs-common --allow-change-held-packages


Create a file filter.yaml:
#@ load("@ytt:overlay", "overlay")

#@overlay/match by=overlay.not_op(overlay.subset({"kind": "ClusterClass"})),expects="0+"
---
#@overlay/remove
  3. Use the default ClusterClass manifest from step 1 to generate the base ClusterClass:
    • ytt -f tkg-vsphere-default-v1.2.0.yaml -f overlays/filter.yaml > default_cc.yaml
  4. Generate the custom ClusterClass this command will apply all files from the folder overlays:
    • ytt -f default_cc.yaml -f overlays/ > custom_cc.yaml
  5. Verify and Install the custom clusterClass in the Management cluster you should see in the file generated the new name and the apt-get install commands in it:
    • kubectl apply -f custom_cc.yaml
  6. You should see the following output when you run kubectl get clusterclasses: 
    • NAME                                  AGE
tkg-vsphere-default-v1.2.0            21h
tkg-vsphere-default-v1.2.0-extended   20h
  7. We have now created an "extended" cluster class that accepts a new variable: nfsCommon

 

In order to create a new cluster with the custom class follow the below steps where the cluster_overlay.yaml is visible below:

#@ load("@ytt:overlay", "overlay")

#@overlay/match by=overlay.subset({"kind":"Cluster"})
---
apiVersion: cluster.x-k8s.io/v1beta1
kind: Cluster
spec:
  topology:
    class: tkg-vsphere-default-v1.2.0-extended
    variables:
    - name: nfsCommon
      value: true

 

  1. Copy the config file to your working director There are multiple ways to complete this step and it is mainly for demo purposes:
    • cp ~/.config/tanzu/tkg/clusterconfigs\{config_file}.yaml ./workload-1.yaml
  2. Generate the custom workload cluster manifest
    • tanzu cluster create --file workload-1.yaml --dry-run > default_cluster.yaml
  3. Using the overlay, create the custom manifest:
    • ytt -f default_cluster.yaml -f cluster_overlay.yaml > custom_cluster.yaml
  4. Deploy
    • tanzu cluster create -f custom_cluster.yaml

For existing clusters the procedure is similar where we have to update two fields on existing cluster:

  1. Modify .spec.topology.class - tkg-vsphere-default-v1.2.0-extended
  2. Add Variable nfsCoommon in .spec.topology.variables as seen in the example below
spec:
...
  topology:
    class: tkg-vsphere-default-v1.2.0-extended
    controlPlane:
      metadata:
        annotations:
          run.tanzu.vmware.com/resolve-os-image: image-type=ova,os-name=ubuntu
      replicas: 1
    variables:
    - name: nfsCommon
      value: true
    - name: cni
      value: antrea
    - name: controlPlaneCertificateRotation
...

The update will trigger immediate update of the worker nodes and will recreate the workers with Nfs-common 

Troubleshooting steps in case the worker nodes are recreated but the NFS client is not installed verify with commands below to confirm if the package was installed successfully

  • journalctl | grep nfs-client
  • journalctl | grep apt-get

Used the below git page as a guide for this KB 

https://github.com/logankimmel/tkgm-nfs-common/tree/master

Additional Information

In case of emergencies, you can manually install the NFS packages temporarily on the worker node.

ssh capv@${WORKER_NODE_IPADDRESS}
sudo add-apt-repository -s https://mirrors.bloomu.edu/ubuntu/ jammy main [mirrors.bloomu.edu] -y
sudo apt update -y
sudo apt-get install -y libnfsidmap1=1:2.6.1-1ubuntu1 --allow-downgrades --allow-change-held-packages
sudo apt-get install -y nfs-common --allow-change-held-packages



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