after using k8s on GKE for a couple of months I've decided to install my own cluster. Now, I've two ubuntu VMs and one of them is the kube-master and the second one is a node. Cluster run as I expect and I can see nodes (kube-master is a node also) when run kubectl get nodes. I've launched one pod each VMs bat I'm experiencing an issue both pod have the same IP. Can anybody help me to resolve this issue? I'm using flannel as network plugin atm.
Thanks in advance
Update
I've found the solution, thanks kubernetes group on slack. I didn't install the [cni][1]plugin so the kubelet didn't know the subnetwork status. I installed the plugin using this guide, made a configuration file following that. Restarted the kubelete service finally I saw the cluster was work as I expected.
Related
I've created a new k8s cluster in a couple of VMware nodes, following this guide:
https://computingforgeeks.com/deploy-kubernetes-cluster-on-ubuntu-with-kubeadm/
After the installation the cluster is up and running, and the master and the node are READY.
So I've created a couple of Pods but I discovered that no one can reach the Internet.
In order to debug I've created the dnsutils Pod (from the Kubernetes page) and
logged into it with "kubectl exec -it pod/dnsutils bash"
If I do a "ping 8.8.8.8" I cannot get any response.
So is it possible that a classic kubernetes installation end up with a cluster unable to reach internet?
What is the fix to do in order to have Pods that "see" Internet?
Any help would be much appreciated
Thanks
\sergio
I've been encountering few major issues with my K8s cluster:
Windows pods running on my Windows nodes are unable to communicate (internally within the cluster) with my linux pods or services. BUT my Linux pods are able to communicate with my Windows pods.
Windows pods are also unable to resolve dns names for any service within K8s
Windows pods are unable to resolve domain names for anything on the internet. Though after opening a shell in the windows pod and manually adding 8.8.8.8 as a DNS server, it would start working
Windows pods are unable to communicate with other pods using the FQDN or ClusterIPs of services created for windows pods.
Things I've verified:
CoreDNS is running
I see no warnings or errors in logs or k8s description of either CoreDNS or Calico pods
I suspect that the issue might be with calico, but I'm quite lost on where to even begin now to troubleshoot these issues. Googling turned up this similar issue, but I've been unsuccessful so far
I've also tried running the following command, but no luck:
kubectl -n kube-system rollout restart deployment coredns
Any ideas any what I can try to take a look at? below is a diagram that I created to try and help visually explain my issue:
I am trying to install a Kubernetes cluster with one master node and two worker nodes.
I acquired 3 VMs for this purpose running on Ubuntu 21.10. In the master node, I installed kubeadm:1.21.4, kubectl:1.21.4, kubelet:1.21.4 and docker-ce:20.4.
I followed this guide to install the cluster. The only difference was in my init command where I did not mention the --control-plane-endpoint. I used calico CNI v3.19.1 and docker for CRI Runtime.
After I installed the cluster, I deployed minio pod and exposed it as a NodePort.
The pod got deployed in the worker node (10.72.12.52) and my master node IP is 10.72.12.51).
For the first two hours, I am able to access the login page via all three IPs (10.72.12.51:30981, 10.72.12.52:30981, 10.72.13.53:30981). However, after two hours, I lost access to the service via 10.72.12.51:30981 and 10.72.13.53:30981. Now I am only able to access the service from the node on which it is running (10.72.12.52).
I have disabled the firewall and added calico.conf file inside /etc/NetworkManager/conf.d with the following content:
[keyfile]
unmanaged-devices=interface-name:cali*;interface-name:tunl*;interface-name:vxlan.calico
What am I missing in the setup that might cause this issue?
This is a community wiki answer posted for better visibility. Feel free to expand it.
As mentioned by #AbhinavSharma the problem was solved by switching from Calico to Flannel CNI.
More information regarding Flannel itself can be found here.
I have just started experimenting with K8S a few days back, try to learn K8S with specific emphasis on networking, service mesh etc.
I am running 2 worker nodes and 1 master on VMs with Centos 7 and K8S, installed with kubeadm.
Default CNI of Flannel. Install was OK and everything except the networking was working. I could deploy containers etc, so a lot of control plane was working.
However, networking not working correctly, even container to container in same worker node. I checked all the usual suspects, the veths, IPs, MACs, briges on a single worker and everything seemed to check out... e.g. MACs where on the correct bridges i.e. cni0, IP address assignments etc. Even when pinging from busybox to busybox, I would see the ARP caches being populated but pings not working still.... disabled all FWs, IP forwarding enabled etc. Not an expert of IPtables but looked OK..... also when logged into the worker node shell I could ping the busybox containers, but they could not ping each other....
One question I have at this point, why is the docker0 bridge still present even when flannel is installed can I delete it or are there some dependencies associated with it ? I did not notice the veths for the containers were showing connected to docker0 bridge but docker bride0 was down... however I followed this website and it show a different way of validating and show veths connected to cni0, which is very confusing and frustrating.....
I gave up Flannel as I was just using Flannel to experiment and decided to try out Calico....
I followed install procedures from Calico site... was not entirely clear on the tidy up procedures for Flannel, not sure where this is documented?... this is where it went from bad to worse...
I started getting crash loops on calico containers and coredns stuck creating, reporting liveliness issues on calico ....and this is where I am stuck......... and would like some help.......
I am have read and tried many things on web and may have fixed some issues as there may be many in play, but would really appreciate any help....
=== install info and some output...
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Some questions...
The Container creating for the coredns..... is this dependent on successful install of Calico... are the issues related.... or should coredns install work independent of the CNI install ?
The Container creating for the coredns..... is this dependent on successful install of Calico... are the issues related.... or should coredns install work independent of the CNI install ?
Yes, it is. You need to install a CNI to have coredns working.
When you setup your cluster with kubeadm there's is a flag called --pod-network-cidr, depending on which CNI you intend to use, you need to specify the range with this flag.
For example, by default, Calico use the range 192.168.0.0/16 and Flannel use the range 10.244.0.0/16.
I have a guide how to setup a cluster using kubeadm, maybe it help you.
Please note, if you want to replace the CNI without delete the entire cluster, extras steps need to be taken in order to "cleanup" the firewall rules from the older CNI.
See here how to replace flannel to calico, for example.
And here how to migrate from flannel to calico.
Since yesterday, I am struggling with this strange issue: node "kmaster" not found.
I tried with multiple combinations of installing kubernetes on jetstream instance.
using calico in ubuntu
using flannel in centos
and few other ways
I looked it online and found many people have the same issue:
https://github.com/kubernetes/kubernetes/issues/61277
If someone ran into a similar issue, then please let me know what steps are needed to be taken to resolve it.
Thanks.
I would recommend to bootstrap Kubernetes cluster from scratch and share with you some helpful links with steps how to proceed:
Kubernetes cluster install on Ubuntu with Calico CNI
Kubernetes cluster install on Centos with Flannel CNI
Keep in mind to fulfill system requirements before you start with kubeadm installation procedure.
You can also take a look at the general kubeadm installation or runtime troubleshooting guide.
I have found my solution for this. I was having issue running kubernetes cluster because the kubernetes components are distributed on multiple servers. Once I created the master node and slave(worker) node on the same machine, the issue got resolved.
The steps that I took to resolve the issue:
1. on slave/worker machine, run this command: kubeadm reset
2. on master node, generate the token by running this command: kubeadm generate token.
3. use the token generated in master machine on the slave node, so that the node machine can join the kubernetes cluster.
Cheers!!