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The ungleich kubernetes infrastructure » History » Version 52

Nico Schottelius, 10/18/2021 10:52 AM

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h1. The ungleich kubernetes infrastructure and ungleich kubernetes manual
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{{toc}}
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h2. Status
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This document is **pre-production**.
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This document is to become the ungleich kubernetes infrastructure overview as well as the ungleich kubernetes manual.
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h2. k8s clusters
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| Cluster         | Purpose/Setup     | Maintainer   | Master(s)                                                | argo | rook | last verified |
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| c0.k8s.ooo      | Dev               | -            | UNUSED                                                   |      |      |    2021-10-05 |
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| c1.k8s.ooo      | Dev p6 VM         | Nico         | 2a0a-e5c0-2-11-0-62ff-fe0b-1a3d.k8s-1.place6.ungleich.ch |      |      |    2021-10-05 |
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| c2.k8s.ooo      | Dev p7 HW         | Nico         | server47 server53 server54                               | x    | x    |    2021-10-05 |
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| c3.k8s.ooo      | Test p7 PI        | -            | UNUSED                                                   |      |      |    2021-10-05 |
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| c4.k8s.ooo      | Dev2 p7 HW        | Fran/Jin-Guk | server52 server53 server54                               |      |      |             - |
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| c5.k8s.ooo      | Dev p6 VM Amal    | Nico/Amal    | 2a0a-e5c0-2-11-0-62ff-fe0b-1a46.k8s-1.place6.ungleich.ch |      |      |               |
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| c6.k8s.ooo      | Dev p6 VM Jin-Guk | Jin-Guk      |                                                          |      |      |               |
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| [[p6.k8s.ooo]]  | production        |              | server67 server69 server71                               | x    | x    |    2021-10-05 |
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| [[p10.k8s.ooo]] | production        |              | server63 server65 server83                               | x    | x    |    2021-10-05 |
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|                 |                   |              |                                                          |      |      |               |
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h2. General architecture and components overview
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* All k8s clusters are IPv6 only
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* We use BGP peering to propagate podcidr and serviceCidr networks to our infrastructure
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* The main public testing repository is "ungleich-k8s":https://code.ungleich.ch/ungleich-public/ungleich-k8s
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** Private configurations are found in the **k8s-config** repository
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h3. Cluster types
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| **Type/Feature**            | **Development**                | **Production**         |
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| Min No. nodes               | 3 (1 master, 3 worker)         | 5 (3 master, 3 worker) |
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| Recommended minimum         | 4 (dedicated master, 3 worker) | 8 (3 master, 5 worker) |
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| Separation of control plane | optional                       | recommended            |
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| Persistent storage          | required                       | required               |
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| Number of storage monitors  | 3                              | 5                      |
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h2. General k8s operations
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h3. Cheat sheet / external great references
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* "kubectl cheatsheet":https://kubernetes.io/docs/reference/kubectl/cheatsheet/
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h3. Get the argocd credentials
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<pre>
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kubectl -n argocd get secret argocd-initial-admin-secret -o jsonpath="{.data.password}" | base64 -d; echo ""
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</pre>
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h3. Get the cluster admin.conf
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* On the masters of each cluster you can find the file @/etc/kubernetes/admin.conf@
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* To be able to administrate the cluster you can copy the admin.conf to your local machine
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* Multi cluster debugging can very easy if you name the config ~/cX-admin.conf (see example below)
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<pre>
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% scp root@server47.place7.ungleich.ch:/etc/kubernetes/admin.conf ~/c2-admin.conf
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% export KUBECONFIG=~/c2-admin.conf    
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% kubectl get nodes
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NAME       STATUS                     ROLES                  AGE   VERSION
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server47   Ready                      control-plane,master   82d   v1.22.0
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server48   Ready                      control-plane,master   82d   v1.22.0
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server49   Ready                      <none>                 82d   v1.22.0
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server50   Ready                      <none>                 82d   v1.22.0
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server59   Ready                      control-plane,master   82d   v1.22.0
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server60   Ready,SchedulingDisabled   <none>                 82d   v1.22.0
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server61   Ready                      <none>                 82d   v1.22.0
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server62   Ready                      <none>                 82d   v1.22.0               
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</pre>
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h3. Installing a new k8s cluster
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* Decide on the cluster name (usually *cX.k8s.ooo*), X counting upwards
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** Using pXX.k8s.ooo for production clusters of placeXX
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* Use cdist to configure the nodes with requirements like crio
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* Decide between single or multi node control plane setups (see below)
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** Single control plane suitable for development clusters
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Typical init procedure:
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* Single control plane: @kubeadm init --config bootstrap/XXX/kubeadm.yaml@
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* Multi control plane (HA): @kubeadm init --config bootstrap/XXX/kubeadm.yaml --upload-certs@
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h3. Deleting a pod that is hanging in terminating state
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<pre>
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kubectl delete pod <PODNAME> --grace-period=0 --force --namespace <NAMESPACE>
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</pre>
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(from https://stackoverflow.com/questions/35453792/pods-stuck-in-terminating-status)
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h3. Listing nodes of a cluster
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<pre>
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[15:05] bridge:~% kubectl get nodes
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NAME       STATUS   ROLES                  AGE   VERSION
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server22   Ready    <none>                 52d   v1.22.0
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server23   Ready    <none>                 52d   v1.22.2
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server24   Ready    <none>                 52d   v1.22.0
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server25   Ready    <none>                 52d   v1.22.0
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server26   Ready    <none>                 52d   v1.22.0
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server27   Ready    <none>                 52d   v1.22.0
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server63   Ready    control-plane,master   52d   v1.22.0
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server64   Ready    <none>                 52d   v1.22.0
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server65   Ready    control-plane,master   52d   v1.22.0
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server66   Ready    <none>                 52d   v1.22.0
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server83   Ready    control-plane,master   52d   v1.22.0
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server84   Ready    <none>                 52d   v1.22.0
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server85   Ready    <none>                 52d   v1.22.0
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server86   Ready    <none>                 52d   v1.22.0
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</pre>
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h3. Removing / draining a node
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Usually @kubectl drain server@ should do the job, but sometimes we need to be more aggressive:
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<pre>
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kubectl drain --delete-emptydir-data --ignore-daemonsets server23
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</pre>
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h3. Readding a node after draining
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<pre>
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kubectl uncordon serverXX
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</pre>
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h3. (Re-)joining worker nodes after creating the cluster
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* We need to have an up-to-date token
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* We use different join commands for the workers and control plane nodes
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Generating the join command on an existing control plane node:
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<pre>
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kubeadm token create --print-join-command
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</pre>
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h3. (Re-)joining control plane nodes after creating the cluster
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* We generate the token again
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* We upload the certificates
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* We need to combine/create the join command for the control plane node
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Example session:
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<pre>
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% kubeadm token create --print-join-command
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kubeadm join p10-api.k8s.ooo:6443 --token xmff4i.ABC --discovery-token-ca-cert-hash sha256:longhash 
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% kubeadm init phase upload-certs --upload-certs
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[upload-certs] Storing the certificates in Secret "kubeadm-certs" in the "kube-system" Namespace
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[upload-certs] Using certificate key:
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CERTKEY
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# Then we use these two outputs on the joining node:
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kubeadm join p10-api.k8s.ooo:6443 --token xmff4i.ABC --discovery-token-ca-cert-hash sha256:longhash --control-plane --certificate-key CERTKEY
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</pre>
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Commands to be used on a control plane node:
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<pre>
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kubeadm token create --print-join-command
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kubeadm init phase upload-certs --upload-certs
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</pre>
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Commands to be used on the joining node:
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<pre>
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JOINCOMMAND --control-plane --certificate-key CERTKEY
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</pre>
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SEE ALSO
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* https://stackoverflow.com/questions/63936268/how-to-generate-kubeadm-token-for-secondary-control-plane-nodes
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* https://blog.scottlowe.org/2019/08/15/reconstructing-the-join-command-for-kubeadm/
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h2. How to fix etcd does not start when rejoining a kubernetes cluster as a control plane
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If during the above step etcd does not come up, @kubeadm join@ can hang as follows:
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<pre>
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[control-plane] Creating static Pod manifest for "kube-apiserver"                                                              
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[control-plane] Creating static Pod manifest for "kube-controller-manager"                                                     
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[control-plane] Creating static Pod manifest for "kube-scheduler"                                                              
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[check-etcd] Checking that the etcd cluster is healthy                                                                         
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error execution phase check-etcd: etcd cluster is not healthy: failed to dial endpoint https://[2a0a:e5c0:10:1:225:b3ff:fe20:37
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8a]:2379 with maintenance client: context deadline exceeded                                                                    
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To see the stack trace of this error execute with --v=5 or higher         
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</pre>
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Then the problem is likely that the etcd server is still a member of the cluster. We first need to remove it from the etcd cluster and then the join works.
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To fix this we do:
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* Find a working etcd pod
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* Find the etcd members / member list
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* Remove the etcd member that we want to re-join the cluster
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<pre>
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# Find the etcd pods
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kubectl -n kube-system get pods -l component=etcd,tier=control-plane
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# Get the list of etcd servers with the member id 
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kubectl exec -n kube-system -ti ETCDPODNAME -- etcdctl --endpoints '[::1]:2379' --cacert /etc/kubernetes/pki/etcd/ca.crt --cert  /etc/kubernetes/pki/etcd/server.crt --key /etc/kubernetes/pki/etcd/server.key member list
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# Remove the member
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kubectl exec -n kube-system -ti ETCDPODNAME -- etcdctl --endpoints '[::1]:2379' --cacert /etc/kubernetes/pki/etcd/ca.crt --cert  /etc/kubernetes/pki/etcd/server.crt --key /etc/kubernetes/pki/etcd/server.key member remove MEMBERID
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</pre>
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Sample session:
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<pre>
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[10:48] line:~% kubectl -n kube-system get pods -l component=etcd,tier=control-plane
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NAME            READY   STATUS    RESTARTS     AGE
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etcd-server63   1/1     Running   0            3m11s
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etcd-server65   1/1     Running   3            7d2h
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etcd-server83   1/1     Running   8 (6d ago)   7d2h
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[10:48] line:~% kubectl exec -n kube-system -ti etcd-server65 -- etcdctl --endpoints '[::1]:2379' --cacert /etc/kubernetes/pki/etcd/ca.crt --cert  /etc/kubernetes/pki/etcd/server.crt --key /etc/kubernetes/pki/etcd/server.key member list
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356891cd676df6e4, started, server65, https://[2a0a:e5c0:10:1:225:b3ff:fe20:375c]:2380, https://[2a0a:e5c0:10:1:225:b3ff:fe20:375c]:2379, false
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371b8a07185dee7e, started, server63, https://[2a0a:e5c0:10:1:225:b3ff:fe20:378a]:2380, https://[2a0a:e5c0:10:1:225:b3ff:fe20:378a]:2379, false
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5942bc58307f8af9, started, server83, https://[2a0a:e5c0:10:1:3e4a:92ff:fe79:bb98]:2380, https://[2a0a:e5c0:10:1:3e4a:92ff:fe79:bb98]:2379, false
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[10:48] line:~% kubectl exec -n kube-system -ti etcd-server65 -- etcdctl --endpoints '[::1]:2379' --cacert /etc/kubernetes/pki/etcd/ca.crt --cert  /etc/kubernetes/pki/etcd/server.crt --key /etc/kubernetes/pki/etcd/server.key member remove 371b8a07185dee7e
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Member 371b8a07185dee7e removed from cluster e3c0805f592a8f77
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</pre>
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SEE ALSO
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* We found the solution using https://stackoverflow.com/questions/67921552/re-installed-node-cannot-join-kubernetes-cluster
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h2. Rook / Ceph Related Operations
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h3. Inspecting the logs of a specific server
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<pre>
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# Get the related pods
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kubectl -n rook-ceph get pods -l app=rook-ceph-osd-prepare 
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...
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# Inspect the logs of a specific pod
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kubectl -n rook-ceph logs -f rook-ceph-osd-prepare-server23--1-444qx
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</pre>
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h3. Triggering server prepare / adding new osds
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The rook-ceph-operator triggers/watches/creates pods to maintain hosts. To trigger a full "re scan", simply delete that pod:
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<pre>
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kubectl -n rook-ceph delete pods -l app=rook-ceph-operator
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</pre>
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This will cause all the @rook-ceph-osd-prepare-..@ jobs to be recreated and thus OSDs to be created, if new disks have been added.
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h3. Removing an OSD
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* See "Ceph OSD Management":https://rook.io/docs/rook/v1.7/ceph-osd-mgmt.html
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h2. Infrastructure versions
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h3. ungleich kubernetes infrastructure v3
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* rook is now installed via helm via argocd instead of directly via manifests
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h3. ungleich kubernetes infrastructure v2
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* Replaced fluxv2 from ungleich k8s v1 with argocd
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** argocd can apply helm templates directly without needing to go through Chart releases
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* We are also using argoflow for build flows
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* Planned to add "kaniko":https://github.com/GoogleContainerTools/kaniko for image building
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h3. ungleich kubernetes infrastructure v1
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We are using the following components:
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* "Calico as a CNI":https://www.projectcalico.org/ with BGP, IPv6 only, no encapsulation
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** Needed for basic networking
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* "kubernetes-secret-generator":https://github.com/mittwald/kubernetes-secret-generator for creating secrets
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** Needed so that secrets are not stored in the git repository, but only in the cluster
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* "ungleich-certbot":https://hub.docker.com/repository/docker/ungleich/ungleich-certbot
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** Needed to get letsencrypt certificates for services
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* "rook with ceph rbd + cephfs":https://rook.io/ for storage
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** rbd for almost everything, *ReadWriteOnce*
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** cephfs for smaller things, multi access *ReadWriteMany*
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** Needed for providing persistent storage
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* "flux v2":https://fluxcd.io/
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** Needed to manage resources automatically