[WIP] Migrating Ceph Nautilus into Kubernetes + Rook

Posted on 2022-08-27 by ungleich storage team

Introduction

At ungleich we are running multiple Ceph clusters. Some of them are running Ceph Nautilus (14.x) based on Devuan. Our newer Ceph Pacific (16.x) clusters are running based on Rook on Kubernetes on top of Alpine Linux.

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 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 or 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.

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 <<EOF

router id $router_id;

log syslog all;
protocol device {
}
 # We are only interested in IPv6, skip another section for IPv4
protocol kernel {
        ipv6 { export all; };
}
protocol bgp k8s {
        local     as 65530;
        neighbor range 2a0a:e5c0::/64 as 65533;
        dynamic name "k8s_"; direct;

        ipv6 {
            import filter { if net.len > 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
<
<!DOCTYPE html>
<html>
<head>
<title>Welcome to nginx!</title>
<style>
    body {
        width: 35em;
        margin: 0 auto;
        font-family: Tahoma, Verdana, Arial, sans-serif;
    }
</style>
</head>
<body>
<h1>Welcome to nginx!</h1>
<p>If you see this page, the nginx web server is successfully installed and
working. Further configuration is required.</p>

<p>For online documentation and support please refer to
<a href="http://nginx.org/">nginx.org</a>.<br/>
Commercial support is available at
<a href="http://nginx.com/">nginx.com</a>.</p>

<p><em>Thank you for using nginx.</em></p>
</body>
</html>
* 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 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.

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.

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



### Original monitors vanish

Did not add bgp peering.
Cannot reach ceph through the routers.

Seems like rook did remove them.

Updating the ceph.conf for the native nodes:

mon host = rook-ceph-mon-a.rook-ceph.svc..,


### Post monitor migration issue 1: OSDs start crashing

A day after the monitor migration some OSDs start to crash. Checking
out the debug log we found the following error:

2022-09-05 10:24:02.881 7fe005ce7700 -1 Processor -- bind unable to bind to v2:[2a0a:e5c0::225:b3ff:fe20:3554]:7300/3712937 on any port in range 6800-7300: (99) Cannot assign requested address 2022-09-05 10:24:02.881 7fe005ce7700 -1 Processor -- bind was unable to bind. Trying again in 5 seconds 2022-09-05 10:24:07.897 7fe005ce7700 -1 Processor -- bind unable to bind to v2:[2a0a:e5c0::225:b3ff:fe20:3554]:7300/3712937 on any port in range 6800-7300: (99) Cannot assign requested address 2022-09-05 10:24:07.897 7fe005ce7700 -1 Processor -- bind was unable to bind after 3 attempts: (99) Cannot assign requested address 2022-09-05 10:24:07.897 7fe0127b1700 -1 received signal: Interrupt from Kernel ( Could be generated by pthread_kill(), raise(), abort(), alarm() ) UID: 0 2022-09-05 10:24:07.897 7fe0127b1700 -1 osd.49 100709 Got signal Interrupt 2022-09-05 10:24:07.897 7fe0127b1700 -1 osd.49 100709 Immediate shutdown (osd_fast_shutdown=true)


Trying to bind to an IPv6 address that is **not** on the system.

https://tracker.ceph.com/issues/24602

Calico/CNI does IP rewriting and thus tells the OSD the wrong IPv6
address.

Adding

public_addr = 2a0a:e5c0::92e2:baff:fe26:642c


to the node. Verifying the binding after restarting the crashing OSD:

[10:35:06] server4.place5:/var/log/ceph# netstat -lnpW | grep 3717792 tcp6 0 0 2a0a:e5c0::92e2:baff:fe26:642c:6821 ::: LISTEN 3717792/ceph-osd tcp6 0 0 :::6822 ::: LISTEN 3717792/ceph-osd tcp6 0 0 :::6823 ::: LISTEN 3717792/ceph-osd tcp6 0 0 2a0a:e5c0::92e2:baff:fe26:642c:6816 ::: LISTEN 3717792/ceph-osd tcp6 0 0 2a0a:e5c0::92e2:baff:fe26:642c:6817 ::: LISTEN 3717792/ceph-osd tcp6 0 0 :::6818 ::: LISTEN 3717792/ceph-osd tcp6 0 0 :::6819 ::: LISTEN 3717792/ceph-osd tcp6 0 0 2a0a:e5c0::92e2:baff:fe26:642c:6820 ::: LISTEN 3717792/ceph-osd unix 2 [ ACC ] STREAM LISTENING 16880318 3717792/ceph-osd /var/run/ceph/ceph-osd.49.asok ```

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.