title: [WIP] Migrating Ceph Nautilus into Kubernetes + Rook --- pub_date: 2022-08-27 --- author: ungleich storage team --- twitter_handle: ungleich --- _hidden: no --- _discoverable: yes --- abstract: How we move our Ceph clusters into kubernetes --- body: ## Introduction At ungleich we are running multiple Ceph clusters. Some of them are running Ceph Nautilus (14.x) based on [Devuan](https://www.devuan.org/). Our newer Ceph Pacific (16.x) clusters are running based on [Rook](https://rook.io/) on [Kubernetes](https://kubernetes.io/) on top of [Alpine Linux](https://alpinelinux.org/). In this blog article we will describe how to migrate Ceph/Native/Devuan to Ceph/k8s+rook/Alpine Linux. ## Work in Progress [WIP] This blog article is work in progress. The migration planning has started, however the migration has not been finished yet. This article will feature the different paths we take for the migration. ## The Plan To continue operating the cluster during the migration, the following steps are planned: * Setup a k8s cluster that can potentially communicate with the existing ceph cluster * Using the [disaster recovery](https://rook.io/docs/rook/v1.9/Troubleshooting/disaster-recovery/) guidelines from rook to modify the rook configuration to use the previous fsid. * Spin up ceph monitors and ceph managers in rook * Retire existing monitors * Shutdown a ceph OSD node, remove it's OS disk, boot it with Alpine Linux * Join the node into the k8s cluster * Have rook pickup the existing disks and start the osds * Repeat if successful * Migrate to ceph pacific ### Original cluster The target ceph cluster we want to migrate lives in the 2a0a:e5c0::/64 network. Ceph is using: ``` public network = 2a0a:e5c0:0:0::/64 cluster network = 2a0a:e5c0:0:0::/64 ``` ### Kubernetes cluster networking inside the ceph network To be able to communicate with the existing OSDs, we will be using sub networks of 2a0a:e5c0::/64 for kubernetes. As these networks are part of the link assigned network 2a0a:e5c0::/64, we will use BGP routing on the existing ceph nodes to create more specific routes into the kubernetes cluster. As we plan to use either [cilium](https://cilium.io/) or [calico](https://www.tigera.io/project-calico/) as the CNI, we can configure kubernetes to directly BGP peer with the existing Ceph nodes. ## The setup ### Kubernetes Bootstrap As usual we bootstrap 3 control plane nodes using kubeadm. The proxy for the API resides in a different kuberentes cluster. We run ``` kubeadm init --config kubeadm.yaml ``` on the first node and join the other two control plane nodes. As usual, joining the workers last. ### k8s Networking / CNI For this setup we are using calico as described in the [ungleich kubernetes manual](https://redmine.ungleich.ch/projects/open-infrastructure/wiki/The_ungleich_kubernetes_infrastructure#section-23). ``` VERSION=v3.23.3 helm repo add projectcalico https://docs.projectcalico.org/charts helm upgrade --install --namespace tigera calico projectcalico/tigera-operator --version $VERSION --create-namespace ``` ### BGP Networking on the old nodes To be able to import the BGP routes from Kubernetes, all old / native hosts will run bird. The installation and configuration is as follows: ``` apt-get update apt-get install -y bird2 router_id=$(hostname | sed 's/server//') cat > /etc/bird/bird.conf < 64 then accept; else reject; }; export none; }; } EOF /etc/init.d/bird restart ``` The router id must be adjusted for every host. As all hosts have a unique number, we use that one as the router id. The bird configuration allows to use dynamic peers so that any k8s node in the network can peer with the old servers. We also use a filter to avoid receiving /64 routes, as they are overlapping with the on link route. ### BGP networking in Kubernetes Calico supports BGP peering and we use a rather standard calico configuration: ``` apiVersion: projectcalico.org/v3 kind: BGPConfiguration metadata: name: default spec: logSeverityScreen: Info nodeToNodeMeshEnabled: true asNumber: 65533 serviceClusterIPs: - cidr: 2a0a:e5c0:0:aaaa::/108 serviceExternalIPs: - cidr: 2a0a:e5c0:0:aaaa::/108 ``` Plus for each server and router we create a BGPPeer: ``` apiVersion: projectcalico.org/v3 kind: BGPPeer metadata: name: serverXX spec: peerIP: 2a0a:e5c0::XX asNumber: 65530 keepOriginalNextHop: true ``` We apply the whole configuration using calicoctl: ``` ./calicoctl create -f - < ~/vcs/k8s-config/bootstrap/p5-cow/calico-bgp.yaml ``` And a few seconds later we can observer the routes on the old / native hosts: ``` bird> show protocols Name Proto Table State Since Info device1 Device --- up 23:09:01.393 kernel1 Kernel master6 up 23:09:01.393 k8s BGP --- start 23:09:01.393 Passive k8s_1 BGP --- up 23:33:01.215 Established k8s_2 BGP --- up 23:33:01.215 Established k8s_3 BGP --- up 23:33:01.420 Established k8s_4 BGP --- up 23:33:01.215 Established k8s_5 BGP --- up 23:33:01.215 Established ``` ### Testing networking To verify that the new cluster is working properly, we can deploy a tiny test deployment and see if it is globally reachable: ``` apiVersion: apps/v1 kind: Deployment metadata: name: nginx-deployment spec: selector: matchLabels: app: nginx replicas: 2 template: metadata: labels: app: nginx spec: containers: - name: nginx image: nginx:1.20.0-alpine ports: - containerPort: 80 ``` And the corresponding service: ``` apiVersion: v1 kind: Service metadata: name: nginx-service spec: selector: app: nginx ports: - protocol: TCP port: 80 ``` Using curl to access a sample service from the outside shows that networking is working: ``` % curl -v http://[2a0a:e5c0:0:aaaa::e3c9] * Trying 2a0a:e5c0:0:aaaa::e3c9:80... * Connected to 2a0a:e5c0:0:aaaa::e3c9 (2a0a:e5c0:0:aaaa::e3c9) port 80 (#0) > GET / HTTP/1.1 > Host: [2a0a:e5c0:0:aaaa::e3c9] > User-Agent: curl/7.84.0 > Accept: */* > * Mark bundle as not supporting multiuse < HTTP/1.1 200 OK < Server: nginx/1.20.0 < Date: Sat, 27 Aug 2022 22:35:49 GMT < Content-Type: text/html < Content-Length: 612 < Last-Modified: Tue, 20 Apr 2021 16:11:05 GMT < Connection: keep-alive < ETag: "607efd19-264" < Accept-Ranges: bytes < Welcome to nginx!

Welcome to nginx!

If you see this page, the nginx web server is successfully installed and working. Further configuration is required.

For online documentation and support please refer to nginx.org.
Commercial support is available at nginx.com.

Thank you for using nginx.

* Connection #0 to host 2a0a:e5c0:0:aaaa::e3c9 left intact ``` So far we have found 1 issue: * Sometimes the old/native servers can reach the service, sometimes they get a timeout In old calico notes on github it is referenced that overlapping Pod/CIDR networks might be a problem. Additionally we cannot use kubeadm to initialise the podsubnet to be a proper subnet of the node subnet: ``` [00:15] server57.place5:~# kubeadm init --service-cidr 2a0a:e5c0:0:cccc::/108 --pod-network-cidr 2a0a:e5c0::/100 I0829 00:16:38.659341 19400 version.go:255] remote version is much newer: v1.25.0; falling back to: stable-1.24 podSubnet: Invalid value: "2a0a:e5c0::/100": the size of pod subnet with mask 100 is smaller than the size of node subnet with mask 64 To see the stack trace of this error execute with --v=5 or higher [00:16] server57.place5:~# ``` ### Networking 2022-09-03 * Instead of trying to merge the cluster networks, we will use separate ranges * According to the [ceph users mailing list discussion](https://www.spinics.net/lists/ceph-users/msg73421.html) it is actually not necessary for mons/osds to be in the same network. In fact, we might be able to remove these settings completely. So today we start with * podSubnet: 2a0a:e5c0:0:14::/64 * serviceSubnet: 2a0a:e5c0:0:15::/108 Using BGP and calico, the kubernetes cluster is setup "as usual" (for ungleich terms). ### Ceph.conf change Originally our ceph.conf contained: ``` public network = 2a0a:e5c0:0:0::/64 cluster network = 2a0a:e5c0:0:0::/64 ``` As of today they are removed and all daemons are restarted, allowing the native cluster to speak with the kubernetes cluster. ### Setting up rook Usually we deploy rook via argocd. However as we want to be easily able to do manual intervention, we will first bootstrap rook via helm directly and turn off various services ``` helm repo add rook https://charts.rook.io/release helm repo update ``` We will use rook 1.8, as it is the last version to support Ceph nautilus, which is our current ceph version. The latest 1.8 version is 1.8.10 at the moment. ``` helm upgrade --install --namespace rook-ceph --create-namespace --version v1.8.10 rook-ceph rook/rook-ceph ``` ### Joining the 2 clusters, step 1: monitors and managers In the first step we want to add rook based monitors and managers and replace the native ones. For rook to be able to talk to our existing cluster, it needs to know * the current monitors/managers ("the monmap") * the right keys to talk to the existing cluster * the fsid As we are using v1.8, we will follow [the guidelines for disaster recover of rook 1.8](https://www.rook.io/docs/rook/v1.8/ceph-disaster-recovery.html). Later we will need to create all the configurations so that rook knows about the different pools. ### Rook: CephCluster Rook has a configuration of type `CephCluster` that typically looks something like this: ``` apiVersion: ceph.rook.io/v1 kind: CephCluster metadata: name: rook-ceph namespace: rook-ceph spec: cephVersion: # see the "Cluster Settings" section below for more details on which image of ceph to run image: quay.io/ceph/ceph:{{ .Chart.AppVersion }} dataDirHostPath: /var/lib/rook mon: count: 5 allowMultiplePerNode: false storage: useAllNodes: true useAllDevices: true onlyApplyOSDPlacement: false mgr: count: 1 modules: - name: pg_autoscaler enabled: true network: ipFamily: "IPv6" dualStack: false crashCollector: disable: false # Uncomment daysToRetain to prune ceph crash entries older than the # specified number of days. daysToRetain: 30 ``` For migrating, we don't want rook in the first stage to create any OSDs. So we will replace `useAllNodes: true` with `useAllNodes: false` and `useAllDevices: true` also with `useAllDevices: false`. ### Extracting a monmap To get access to the existing monmap, we can export it from the native cluster using `ceph-mon -i {mon-id} --extract-monmap {map-path}`. More details can be found on the [documentation for adding and removing ceph monitors](https://docs.ceph.com/en/latest/rados/operations/add-or-rm-mons/). ### Rook and Ceph pools Rook uses `CephBlockPool` to describe ceph pools as follows: ``` apiVersion: ceph.rook.io/v1 kind: CephBlockPool metadata: name: hdd namespace: rook-ceph spec: failureDomain: host replicated: size: 3 deviceClass: hdd ``` In this particular cluster we have 2 pools: - one (ssd based, device class = ssd) - hdd (hdd based, device class = hdd-big) The device class "hdd-big" is specific to this cluster as it used to contain 2.5" and 3.5" HDDs in different pools. ### [old] Analysing the ceph cluster configuration Taking the view from the old cluster, the following items are important for adding new services/nodes: * We have a specific fsid that needs to be known * The expectation would be to find that fsid in a configmap/secret in rook * We have a list of running monitors * This is part of the monmap and ceph.conf * ceph.conf is used for finding the initial contact point * Afterwards the information is provided by the monitors * For rook it would be expected to have a configmap/secret listing the current monitors * The native clusters have a "ceph.client.admin.keyring" deployed which allows adding and removing resources. * Rook probably has a secret for keyrings * Maybe multiple depending on how services are organised ### Analysing the rook configurations Taking the opposite view, we can also checkout a running rook cluster and the rook disaster recovery documentation to identify what to modify. Let's have a look at the secrets first: ``` cluster-peer-token-rook-ceph kubernetes.io/rook 2 320d default-token-xm9xs kubernetes.io/service-account-token 3 320d rook-ceph-admin-keyring kubernetes.io/rook 1 320d rook-ceph-admission-controller kubernetes.io/tls 3 29d rook-ceph-cmd-reporter-token-5mh88 kubernetes.io/service-account-token 3 320d rook-ceph-config kubernetes.io/rook 2 320d rook-ceph-crash-collector-keyring kubernetes.io/rook 1 320d rook-ceph-mgr-a-keyring kubernetes.io/rook 1 320d rook-ceph-mgr-b-keyring kubernetes.io/rook 1 320d rook-ceph-mgr-token-ktt2m kubernetes.io/service-account-token 3 320d rook-ceph-mon kubernetes.io/rook 4 320d rook-ceph-mons-keyring kubernetes.io/rook 1 320d rook-ceph-osd-token-8m6lb kubernetes.io/service-account-token 3 320d rook-ceph-purge-osd-token-hznnk kubernetes.io/service-account-token 3 320d rook-ceph-rgw-token-wlzbc kubernetes.io/service-account-token 3 134d rook-ceph-system-token-lxclf kubernetes.io/service-account-token 3 320d rook-csi-cephfs-node kubernetes.io/rook 2 320d rook-csi-cephfs-plugin-sa-token-hkq2g kubernetes.io/service-account-token 3 320d rook-csi-cephfs-provisioner kubernetes.io/rook 2 320d rook-csi-cephfs-provisioner-sa-token-tb78d kubernetes.io/service-account-token 3 320d rook-csi-rbd-node kubernetes.io/rook 2 320d rook-csi-rbd-plugin-sa-token-dhhq6 kubernetes.io/service-account-token 3 320d rook-csi-rbd-provisioner kubernetes.io/rook 2 320d rook-csi-rbd-provisioner-sa-token-lhr4l kubernetes.io/service-account-token 3 320d ``` TBC ### Creating additional resources after the cluster is bootstrapped To let rook know what should be there, we already create the two `CephBlockPool` instances that match the existing pools: ```apiVersion: ceph.rook.io/v1 kind: CephBlockPool metadata: name: one namespace: rook-ceph spec: failureDomain: host replicated: size: 3 deviceClass: ssd ``` And for the hdd based pool: ``` apiVersion: ceph.rook.io/v1 kind: CephBlockPool metadata: name: hdd namespace: rook-ceph spec: failureDomain: host replicated: size: 3 deviceClass: hdd-big ``` Saving both of these in ceph-blockpools.yaml and applying it: ``` kubectl -n rook-ceph apply -f ceph-blockpools.yaml ``` ### Configuring ceph after the operator deployment As soon as the operator and the crds have been deployed, we deploy the following [CephCluster](https://rook.io/docs/rook/v1.8/ceph-cluster-crd.html) configuration: ``` apiVersion: ceph.rook.io/v1 kind: CephCluster metadata: name: rook-ceph namespace: rook-ceph spec: cephVersion: image: quay.io/ceph/ceph:v14.2.21 dataDirHostPath: /var/lib/rook mon: count: 5 allowMultiplePerNode: false storage: useAllNodes: false useAllDevices: false onlyApplyOSDPlacement: false mgr: count: 1 modules: - name: pg_autoscaler enabled: true network: ipFamily: "IPv6" dualStack: false crashCollector: disable: false # Uncomment daysToRetain to prune ceph crash entries older than the # specified number of days. daysToRetain: 30 ``` We wait for the cluster to initialise and stabilise before applying changes. Important to note is that we use the ceph image version v14.2.21, which is the same version as the native cluster. ### rook v1.8 is incompatible with ceph nautilus After deploying the rook operator, the following error message is printed in its logs: ``` 2022-09-03 15:14:03.543925 E | ceph-cluster-controller: failed to reconcile CephCluster "rook-ceph/rook-ceph". failed to reconcile cluster "rook-ceph": failed to configure local ceph cluster: failed the ceph version check: the version does not meet the minimum version "15.2.0-0 octopus" ``` So we need to downgrade to rook v1.7. Using `helm search repo rook/rook-ceph --versions` we identify the latest usable version should be `v1.7.11`. We start the downgrade process using ``` helm upgrade --install --namespace rook-ceph --create-namespace --version v1.7.11 rook-ceph rook/rook-ceph ``` After downgrading the operator is starting the canary monitors and continues to bootstrap the cluster. ### The ceph-toolbox To be able to view the current cluster status, we also deploy the ceph-toolbox for interacting with rook: ``` apiVersion: apps/v1 kind: Deployment metadata: name: rook-ceph-tools namespace: rook-ceph # namespace:cluster labels: app: rook-ceph-tools spec: replicas: 1 selector: matchLabels: app: rook-ceph-tools template: metadata: labels: app: rook-ceph-tools spec: dnsPolicy: ClusterFirstWithHostNet containers: - name: rook-ceph-tools image: rook/ceph:v1.7.11 command: ["/bin/bash"] args: ["-m", "-c", "/usr/local/bin/toolbox.sh"] imagePullPolicy: IfNotPresent tty: true securityContext: runAsNonRoot: true runAsUser: 2016 runAsGroup: 2016 env: - name: ROOK_CEPH_USERNAME valueFrom: secretKeyRef: name: rook-ceph-mon key: ceph-username - name: ROOK_CEPH_SECRET valueFrom: secretKeyRef: name: rook-ceph-mon key: ceph-secret volumeMounts: - mountPath: /etc/ceph name: ceph-config - name: mon-endpoint-volume mountPath: /etc/rook volumes: - name: mon-endpoint-volume configMap: name: rook-ceph-mon-endpoints items: - key: data path: mon-endpoints - name: ceph-config emptyDir: {} tolerations: - key: "node.kubernetes.io/unreachable" operator: "Exists" effect: "NoExecute" tolerationSeconds: 5 ``` ### Checking the deployments After the rook-operator finished deploying, the following deployments are visible in kubernetes: ``` [17:25] blind:~% kubectl -n rook-ceph get deployment NAME READY UP-TO-DATE AVAILABLE AGE csi-cephfsplugin-provisioner 2/2 2 2 21m csi-rbdplugin-provisioner 2/2 2 2 21m rook-ceph-crashcollector-server48 1/1 1 1 2m3s rook-ceph-crashcollector-server52 1/1 1 1 2m24s rook-ceph-crashcollector-server53 1/1 1 1 2m2s rook-ceph-crashcollector-server56 1/1 1 1 2m17s rook-ceph-crashcollector-server57 1/1 1 1 2m1s rook-ceph-mgr-a 1/1 1 1 2m3s rook-ceph-mon-a 1/1 1 1 10m rook-ceph-mon-b 1/1 1 1 8m3s rook-ceph-mon-c 1/1 1 1 5m55s rook-ceph-mon-d 1/1 1 1 5m33s rook-ceph-mon-e 1/1 1 1 4m32s rook-ceph-operator 1/1 1 1 102m rook-ceph-tools 1/1 1 1 17m ``` Relevant for us are the mgr, mon and operator. To stop the cluster, we will shutdown the deployments in the following order: * rook-ceph-operator: to prevent deployments to recover ### Data / configuration comparison Logging into a host that is running mon-a, we find the following data in it: ``` [17:36] server56.place5:/var/lib/rook# find . ./mon-a ./mon-a/data ./mon-a/data/keyring ./mon-a/data/min_mon_release ./mon-a/data/store.db ./mon-a/data/store.db/LOCK ./mon-a/data/store.db/000006.log ./mon-a/data/store.db/000004.sst ./mon-a/data/store.db/CURRENT ./mon-a/data/store.db/MANIFEST-000005 ./mon-a/data/store.db/OPTIONS-000008 ./mon-a/data/store.db/OPTIONS-000005 ./mon-a/data/store.db/IDENTITY ./mon-a/data/kv_backend ./rook-ceph ./rook-ceph/crash ./rook-ceph/crash/posted ./rook-ceph/log ``` Which is pretty similar to the native nodes: ``` [17:37:50] red3.place5:/var/lib/ceph/mon/ceph-red3# find . ./sysvinit ./keyring ./min_mon_release ./kv_backend ./store.db ./store.db/1959645.sst ./store.db/1959800.sst ./store.db/OPTIONS-3617174 ./store.db/2056973.sst ./store.db/3617348.sst ./store.db/OPTIONS-3599785 ./store.db/MANIFEST-3617171 ./store.db/1959695.sst ./store.db/CURRENT ./store.db/LOCK ./store.db/2524598.sst ./store.db/IDENTITY ./store.db/1959580.sst ./store.db/2514570.sst ./store.db/1959831.sst ./store.db/3617346.log ./store.db/2511347.sst ``` ### Checking how monitors are created on native ceph To prepare for the migration we take 1 step back and verify how monitors are created in the native cluster. The script used for monitoring creation can be found on [code.ungleich.ch](https://code.ungleich.ch/ungleich-public/ungleich-tools/src/branch/master/ceph/ceph-mon-create-start) and contains the following logic: * get "mon." key * get the monmap * Run ceph-mon --mkfs using the monmap and keyring * Start it In theory we could re-use these steps on a rook deployed monitor to join our existing cluster. ### Checking the toolbox and monitor pods for migration When the ceph-toolbox is deployed, we get a ceph.conf and a keyring in /ect/ceph. The keyring is actually the admin keyring and allows us to make modifications to the ceph cluster. The ceph.conf points to the monitors and does not contain an fsid. The ceph-toolbox gets this informatoin via 1 configmap ("rook-ceph-mon-endpoints") and a secret ("rook-ceph-mon"). The monitor pods on the other hand have an empty ceph.conf and no admin keyring deployed. ### Try 1: recreating a monitor inside the existing cluster Let's try to reuse an existing monitor and join it into the existing cluster. For this we will first shut down the rook-operator, to prevent it to intefere with our migration. Then modify the relevant configmaps and secrets and import the settings from the native cluster. Lastly we will patch one of the monitor pods, inject the monmap from the native cluster and then restart it. Let's give it a try. First we shutdown the rook-ceph-operator: ``` % kubectl -n rook-ceph scale --replicas=0 deploy/rook-ceph-operator deployment.apps/rook-ceph-operator scaled ``` Then we patch the mon deployments to not run a monitor, but only sleep: ``` for mon in a b c d e; do kubectl -n rook-ceph patch deployment rook-ceph-mon-${mon} -p \ '{"spec": {"template": {"spec": {"containers": [{"name": "mon", "command": ["sleep", "infinity"], "args": []}]}}}}'; kubectl -n rook-ceph patch deployment rook-ceph-mon-$mon --type='json' -p '[{"op":"remove", "path":"/spec/template/spec/containers/0/livenessProbe"}]' done ``` No the pod is restarted and when we execute into it, we will see that no monitor is running in it: ``` % kubectl -n rook-ceph exec -ti rook-ceph-mon-a-c9f8f554b-2fkhm -- sh Defaulted container "mon" out of: mon, chown-container-data-dir (init), init-mon-fs (init) sh-4.2# ps aux USER PID %CPU %MEM VSZ RSS TTY STAT START TIME COMMAND root 1 0.0 0.0 4384 664 ? Ss 19:44 0:00 sleep infinity root 7 0.0 0.0 11844 2844 pts/0 Ss 19:44 0:00 sh root 13 0.0 0.0 51752 3384 pts/0 R+ 19:44 0:00 ps aux sh-4.2# ``` Now for this pod to work with our existing cluster, we want to import the monmap and join the monitor to the native cluster. As with any mon, the data is stored below `/var/lib/ceph/mon/ceph-a/`. Before importing the monmap, let's have a look at the different rook configurations that influence the ceph components ### Looking at the ConfigMap in detail: rook-ceph-mon-endpoints As the name says, it contains the list of monitor endpoints: ``` kubectl -n rook-ceph edit configmap rook-ceph-mon-endpoints ... csi-cluster-config-json: '[{"clusterID":"rook-ceph","monitors":["[2a0a:e5c0:0:15::fc2]:6789"... data: b=[2a0a:e5c0:0:15::9cd9]:6789,.... mapping: '{"node":{"a":{"Name":"server56","Hostname":"server56","Address":"2a0a:e5c0::... ``` As eventually we want the cluster and csi to use the in-cluster monitors, we don't need to modify it right away. ### Looking at Secrets in detail: rook-ceph-admin-keyring The first interesting secret is **rook-ceph-admin-keyring**, which contains the admin keyring. The old one of course, so we can edit this secret and replace it with the client.admin secret from our native cluster. We encode the original admin keyring using: ``` cat ceph.client.admin.keyring | base64 -w 0; echo "" ``` And then we update the secret it: ``` kubectl -n rook-ceph edit secret rook-ceph-admin-keyring ``` [done] ### Looking at Secrets in detail: rook-ceph-config This secret contains two keys, **mon_host** and **mon_initial_members**. The **mon_host** is a list of monitor addresses. The **mon_host** only contains the monitor names, a, b, c, d and e. The environment variable **ROOK_CEPH_MON_HOST** in the monitor deployment is set to to **mon_host** key of that secret, so monitors will read from it. ### Looking at Secrets in detail: rook-ceph-mon This secret contains the following interesting keys: * ceph-secret: the admin key (just the base64 key no section around it) [done] * ceph-username: "client.admin" * fsid: the ceph cluster fsid * mon-secret: The key of the [mon.] section It's important to mention to use `echo -n` when inserting the keys or fsids. [done] ### Looking at Secrets in detail: rook-ceph-mons-keyring Contains the key "keyring" containing the [mon.] and [client.admin] sections: ``` [mon.] key = ... [client.admin] key = ... caps mds = "allow" caps mgr = "allow *" caps mon = "allow *" caps osd = "allow *" ``` Using `base64 -w0 < ~/mon-and-client`. [done] ### Importing the monmap Getting the current monmap from the native cluster: ``` ceph mon getmap -o monmap-20220903 scp root@old-monitor:monmap-20220903 ``` Adding it into the mon pod: ``` kubectl cp monmap-20220903 rook-ceph/rook-ceph-mon-a-6c46d4694-kxm5h:/tmp ``` Moving the old mon db away: ``` cd /var/lib/ceph/mon/ceph-a mkdir _old mv [a-z]* _old/ ``` Recreating the mon fails, as the volume is mounted directly onto it: ``` % ceph-mon -i a --mkfs --monmap /tmp/monmap-20220903 --keyring /tmp/mon-key 2022-09-03 21:44:48.268 7f1a738f51c0 -1 '/var/lib/ceph/mon/ceph-a' already exists and is not empty: monitor may already exist % mount | grep ceph-a /dev/sda1 on /var/lib/ceph/mon/ceph-a type ext4 (rw,relatime) ``` We can workaround this by creating all monitors on pods with other names. So we can create mon b to e on the mon-a pod and mon-a on any other pod. On rook-ceph-mon-a: ``` for mon in b c d e; do ceph-mon -i $mon --mkfs --monmap /tmp/monmap-20220903 --keyring /tmp/mon-key; done ``` On rook-ceph-mon-b: ``` mon=a ceph-mon -i $mon --mkfs --monmap /tmp/monmap-20220903 --keyring /tmp/mon-key ``` Then we export the newly created mon dbs: ``` for mon in b c d e; do kubectl cp rook-ceph/rook-ceph-mon-a-6c46d4694-kxm5h:/var/lib/ceph/mon/ceph-$mon ceph-$mon; done ``` ``` for mon in a; do kubectl cp rook-ceph/rook-ceph-mon-b-57d888dd9f-w8jkh:/var/lib/ceph/mon/ceph-$mon ceph-$mon; done ``` And finally we test it by importing the mondb to mon-a: ``` kubectl cp ceph-a rook-ceph/rook-ceph-mon-a-6c46d4694-kxm5h:/var/lib/ceph/mon/ ``` And the other mons: ``` kubectl cp ceph-b rook-ceph/rook-ceph-mon-b-57d888dd9f-w8jkh:/var/lib/ceph/mon/ ``` ### Re-enabling the rook-operator As the deployment ``` kubectl -n rook-ceph scale --replicas=1 deploy/rook-ceph-operator ``` Operator sees them running (with a shell) ``` 2022-09-03 22:29:26.725915 I | op-mon: mons running: [d e a b c] ``` Triggering recreation: ``` % kubectl -n rook-ceph delete deployment rook-ceph-mon-a deployment.apps "rook-ceph-mon-a" deleted ``` Connected successfully to the cluster: ``` services: mon: 6 daemons, quorum red1,red2,red3,server4,server3,a (age 8s) mgr: red3(active, since 8h), standbys: red2, red1, server4 osd: 46 osds: 46 up, 46 in ``` A bit later: ``` mon: 8 daemons, quorum (age 2w), out of quorum: red1, red2, red3, server4, server3, a, c, d mgr: red3(active, since 8h), standbys: red2, red1, server4 osd: 46 osds: 46 up, 46 in ``` And a little bit later also the mgr joined the cluster: ``` services: mon: 8 daemons, quorum red2,red3,server4,server3,a,c,d,e (age 46s) mgr: red3(active, since 9h), standbys: red1, server4, a, red2 osd: 46 osds: 46 up, 46 in ``` And a few minutes later all mons joined successfully: ``` mon: 8 daemons, quorum red3,server4,server3,a,c,d,e,b (age 31s) mgr: red3(active, since 105s), standbys: red1, server4, a, red2 osd: 46 osds: 46 up, 46 in ``` We also need to ensure the toolbox is being updated/recreated: ``` kubectl -n rook-ceph delete pods rook-ceph-tools-5cf88dd58f-fwwlc ``` ### Retiring the old monitors ### The actual migration At this point we have 2 ceph clusters: * A new one in rook * The old/native one The next steps are: Replace fsid in secrets/rook-ceph-mon with that of the old one. ## Changelog ### 2022-09-03 * Next try starting for migration * Looking deeper into configurations ### 2022-08-29 * Added kubernetes/kubeadm bootstrap issue ### 2022-08-27 * The initial release of this blog article * Added k8s bootstrapping guide ## Follow up or questions You can join the discussion in the matrix room `#kubernetes:ungleich.ch` about this migration. If don't have a matrix account you can join using our chat on https://chat.with.ungleich.ch.