Expert Training in Kubernetes and Rancher Join our free online training sessions to learn how to manage Kubernetes workloads with Rancher. In this post, you will go from 3 Ubuntu 16.04 nodes to a basic Kubernetes cluster in a few simple steps. To accomplish this, you will be using Rancher Kubernetes Engine (RKE). To be able to use RKE, you will need 3 Linux nodes with Docker installed (see Requirements below). This won’t be a production ready cluster, but enough to get you familiar with RKE, some Kubernetes and be able to play around with the cluster.
- Cant Ping Services Using Dns Inside Kubernetes Clusters
- Can't Ping Services Using Dns Inside Kubernetes Cluster
- Can't ping services or pods #7996. I can't ping the service from any node at all. --cluster_dns=192.168.3.10 --cluster_domain=kubernetes.local.
- DNS for your OpenShift v3 cluster. By Luke Meyer November 19. The internal SkyDNS server that resolves the local cluster URLs like kubernetes.default.svc.cluster.local. By default Kubernetes already injects this server IP into containers; we want to keep the existing resolution but also add hostnames and domain names. # Reverse DNS.
Keep an eye out for the post for building a production ready cluster. Requirements.
RKE You will be using RKE from your workstation. Download the latest version for your platform at:. kubectl After creating the cluster, we will use the default Kubernetes command-line tool called kubectl to interact with the cluster. Get the latest version for your platform at:. 3 Ubuntu 16.04 nodes with 2(v)CPUs, 4GB of memory and with swap disabled Most commonly used Linux distribution is Ubuntu 16.04, this is what will be used in this post. Make sure swap is disabled by running swapoff -a and removing any swap entry in /etc/fstab.
You must be able to access the node using SSH. As this is a multi-node cluster, need to be opened before proceeding. Docker installed on each Linux node Kubernetes only validates Docker up to 17.03.2 (See ). You can use to install Docker (make sure you install 17.03.2) or use this one-liner to install the correct version: curl sh Make sure the requirements listed above are fulfilled before you proceed. How RKE works RKE can be run from any platform (the binary is available for MacOS/Linux/Windows), in this example it will run on your workstation/laptop/computer.
However, almost every container deployed cannot resolve dns outside. Using the CentOS documentation provides no kube-system namespace services. Pinging any domain from one of the few images that actually starts. The only systems that have issues are pods in the kubernetes internal network.
The examples in this post are based on MacOS/Linux. RKE will connect to the nodes using a configured SSH private key (the nodes should have the matching SSH public key installed for the SSH user) and setup a tunnel to access the Docker socket (/var/run/docker.sock by default, but configurable). This means that the configured SSH user must have access to the Docker socket on the machine, we will go over this in Creating the Linux user account. Creating the Linux user account Note: Make sure Docker is installed following the instructions in the Requirements section above. The following steps need to be executed on every node. If you need to use sudo, prefix each command with sudo.
If you already have users that can access the machine using a SSH key and can access the Docker socket, you can skip this step. $ ssh-keygen Generating public/private rsa key pair. Enter file in which to save the key ($HOME/.ssh/idrsa): Enter passphrase (empty for no passphrase): Enter same passphrase again: Your identification has been saved in $HOME/.ssh/idrsa. Your public key has been saved in $HOME/.ssh/idrsa.pub. The key fingerprint is: xxx After creating the SSH key pair, you should have the following files:. $HOME/.ssh/idrsa (SSH private key, keep this secure).
$HOME/.ssh/idrsa.pub (SSH public key) Copy the SSH public key to the nodes To be able to access the nodes using the created SSH key pair, you will need to install the SSH public key onto the nodes. Execute this for every node (where hostname is the IP/hostname of the node). # Install the SSH public key on the node $ cat $HOME/.ssh/idrsa.pub ssh hostname 'sudo tee -a /home/rke/.ssh/authorizedkeys' Note: This post is demonstrating how you create a separate user for RKE. Because of this, we can’t use ssh-copy-id as it only works for installing keys to the same user as is used for the SSH connection. Setup ssh-agent Note: If you chose not to put a passphrase on your SSH private key, you can skip this step. This needs to be executed on your workstation/laptop/computer. $ ssh -i $HOME/.ssh/idrsa docker version Client: Version: 17.03.2-ce API version: 1.27 Go version: go1.7.5 Git commit: f5ec1e2 Built: Tue Jun 27 03: OS/Arch: linux/amd64 Server: Version: 17.03.2-ce API version: 1.27 (minimum version 1.12) Go version: go1.7.5 Git commit: f5ec1e2 Built: Tue Jun 27 03: OS/Arch: linux/amd64 Experimental: false Configuring and running RKE Get RKE for your platform at:.
RKE will run on your workstation/laptop/computer. For this post I’ve renamed the RKE binary to rke, to make the commands generic for each platform. You can do the same by running.
# Download RKE for MacOS (Darwin) $ wget # Rename binary to rke mv rkedarwin-amd64 rke # Make RKE binary executable $ chmod +x rke # Show RKE version $./rke -version rke version v0.1.9 Next step is to create a cluster configuration file (by default it will be cluster.yml). This contains all information to build the Kubernetes cluster, like node connection info, what roles to apply to what node etcetera. All can be found in the documentation.
You can create the cluster configuration file by running./rke config and answering the questions. For this post, you will create a 3 node cluster with every role on each node (answer y for every role), and we will add the Kubernetes Dashboard as addon (Using ). To access the Kubernetes Dashboard, you need a Service Account token which will be created by adding to the addons.
Cant Ping Services Using Dns Inside Kubernetes Clusters
Regarding answering the question to create the cluster configuration file:. The values in brackets, for instance 22 for SSH Port, are defaults and can just be used by pressing the Enter key. The default SSH Private Key would do, if you have another key, please change it. $./rke config + Cluster Level SSH Private Key Path /.ssh/idrsa: /.ssh/idrsa + Number of Hosts 1: 3 + SSH Address of host (1) none: ipordnshost1 + SSH Port of host (1) 22: + SSH Private Key Path of host (ipordnshost1) none: - You have entered empty SSH key path, trying fetch from SSH key parameter + SSH Private Key of host (ipordnshost1) none: - You have entered empty SSH key, defaulting to cluster level SSH key: /.ssh/idrsa + SSH User of host (ipordnshost1) ubuntu: rke + Is host (ipordnshost1) a Control Plane host (y/n)? y: y + Is host (ipordnshost1) a Worker host (y/n)? n: y + Is host (ipordnshost1) an etcd host (y/n)?
$./rke up INFO0000 Building Kubernetes cluster. INFO0151 Finished building Kubernetes cluster successfully If all went well, you should have a lot of output from the command but it should end with Finished building Kubernetes cluster successfully. It will also write a kubeconfig file as kubeconfigcluster.yml. You can use that file to connect to your Kubernetes cluster. Exploring your Kubernetes cluster Make sure you have kubectl installed, see how to get it for your platform. Note: When running kubectl, it automatically tries to use a kubeconfig from the default location; $HOME/.kube/config.
In the examples, we explicitly specify the kubeconfig file using -kubeconfig kubeconfigcluster.yml. If you don’t want to specify the kubeconfig file every time, you can copy the file kubeconfigcluster.yml to $HOME/.kube/config. (you probably need to create the directory $HOME/.kube first) Start with querying the server for its version. $ kubectl -kubeconfig kubeconfigcluster.yml get deploy -n kube-system -l k8s-app=kubernetes-dashboard NAME DESIRED CURRENT UP-TO-DATE AVAILABLE AGE kubernetes-dashboard 1 1 1 1 17m By default, the deployments are not exposed to the outside. If you want to visit the Kubernetes Dashboard in your browser, you will need to expose the deployment externally (which we will do in our demo application later) or use the built-in proxy functionality of kubectl.
This will open the 127.0.0.1:8001 (your local machine on port 8001) and tunnel it to the Kubernetes cluster. Before you can visit the Kubernetes Dashboard, you need to retrieve the token to login to the dashboard. By default, it runs under a very limited account and will not be able to show you all the resources in your cluster.
The second addon we added when creating the cluster configuration file created the account and token we need (this is based upon ) You can retrieve the token by running. $ kubectl -kubeconfig kubeconfigcluster.yml proxy Starting to serve on 127.0.0.1:8001 And open the following URL: When prompted for login, choose Token, paste the token and click Sign In. Note: When you don’t get a login screen, open it manually by clicking Sign In on the top right. Run a demo application Last step of this post, running a demo application and exposing it. For this example you will run a demo application superseb/rancher-demo, which is a web UI showing the scale of a deployment. It will be exposed using an Ingress, which is handled by the NGINX Ingress controller that is deployed by default.
If you want to know more about Ingress, please see Start by deploying and exposing the demo application (which runs on port 8080). $ kubectl -kubeconfig kubeconfigcluster.yml rollout status deployment/rancher-demo. Deployment 'rancher-demo' successfully rolled out The command kubectl run is the easiest way to get a container running on your cluster. It takes an image parameter to specify the Docker image and a name at minimum.
In this case, we also want to configure the port that this container exposes (internally), and expose it. What happened was that there was a Deployment created (and a ReplicaSet) with a scale of 1 (default), and a Service was created to abstract access to the pods (which can contain one or more containers, in this case 1). For more information on these subjects check the following links:. RKE deploys the NGINX Ingress controller by default on every node. This opens op port 80 and port 443, and can serve as main entrypoint for any created Ingress. An Ingress can contain a single host or multiple, multiple paths, and you can configure SSL certificates. In this post you will configure a basic Ingress, making our demo application accessible on a certain hostname.
In the example we will use rancher-demo.domain.test as hostname to access the demo application. Note: To access our test domain you have to add the domain name to /etc/hosts to visit the UI, as it’s not a valid DNS name. If you have access to your own domain, you can add a DNS A record pointing to each of the nodes. The only part that is not created, is the Ingress. Let’s create an Ingress calledrancher-demo-ingress, having a host specification to match requests to our test domain (rancher-demo.domain.test), and pointing it to our Service called rancher-demo on port 8080.
Save the following content to a file called ingress.yml. $ kubectl -kubeconfig kubeconfigcluster.yml scale deploy/rancher-demo -replicas=10 deployment.extensions/rancher-demo scaled Note: Make sure to clean up the /etc/hosts entry when you are done. Closing words This started as a post how to create a Kubernetes cluster in under 10 minutes, but along the way I tried to add some useful information how certain parts work. To avoid having a post that takes a day to read (explaining every part), there will be other posts describing certain parts. For now, I’ve linked as much resources as possible to existing documentation where you can learn more.
Can't Ping Services Using Dns Inside Kubernetes Cluster
John Belamaric Published: 8 May, 2017 and tagged, and using 881 words. Related Content. – 3 minutes. – 3 minutes. – 3 minutes.
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Last modified: 26 Aug, 2018 Copyright © 2019 The CoreDNS Authors. Copyright © 2019 The Linux Foundation速. All rights reserved. The Linux Foundation has registered trademarks and uses trademarks. For a list of trademarks of The Linux Foundation.
Resolved via. It basically is all the way down.