Kubernetesの基本を学ぶ

はじめに

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Google Compute Engine上でKubernetesを動かす

The example below creates a Kubernetes cluster with 3 worker node Virtual Machines and a master Virtual Machine (i.e. 4 VMs in your cluster). This cluster is set up and controlled from your workstation (or wherever you find convenient).

始める前に

If you want a simplified getting started experience and GUI for managing clusters, please consider trying Google Kubernetes Engine for hosted cluster installation and management.

For an easy way to experiment with the Kubernetes development environment, click the button below to open a Google Cloud Shell with an auto-cloned copy of the Kubernetes source repo.

Open in Cloud Shell

If you want to use custom binaries or pure open source Kubernetes, please continue with the instructions below.

前提条件

  1. You need a Google Cloud Platform account with billing enabled. Visit the Google Developers Console for more details.
  2. Install gcloud as necessary. gcloud can be installed as a part of the Google Cloud SDK.
  3. Enable the Compute Engine Instance Group Manager API in the Google Cloud developers console.
  4. Make sure that gcloud is set to use the Google Cloud Platform project you want. You can check the current project using gcloud config list project and change it via gcloud config set project <project-id>.
  5. Make sure you have credentials for GCloud by running gcloud auth login.
  6. (Optional) In order to make API calls against GCE, you must also run gcloud auth application-default login.
  7. Make sure you can start up a GCE VM from the command line. At least make sure you can do the Create an instance part of the GCE Quickstart.
  8. Make sure you can SSH into the VM without interactive prompts. See the Log in to the instance part of the GCE Quickstart.

クラスターの起動

You can install a client and start a cluster with either one of these commands (we list both in case only one is installed on your machine):

curl -sS https://get.k8s.io | bash

or

wget -q -O - https://get.k8s.io | bash

Once this command completes, you will have a master VM and four worker VMs, running as a Kubernetes cluster.

By default, some containers will already be running on your cluster. Containers like fluentd provide logging, while heapster provides monitoring services.

The script run by the commands above creates a cluster with the name/prefix “kubernetes”. It defines one specific cluster config, so you can’t run it more than once.

Alternately, you can download and install the latest Kubernetes release from this page, then run the <kubernetes>/cluster/kube-up.sh script to start the cluster:

cd kubernetes
cluster/kube-up.sh

If you want more than one cluster running in your project, want to use a different name, or want a different number of worker nodes, see the <kubernetes>/cluster/gce/config-default.sh file for more fine-grained configuration before you start up your cluster.

If you run into trouble, please see the section on troubleshooting, post to the Kubernetes Forum, or come ask questions on Slack.

The next few steps will show you:

  1. How to set up the command line client on your workstation to manage the cluster
  2. Examples of how to use the cluster
  3. How to delete the cluster
  4. How to start clusters with non-default options (like larger clusters)

ワークステーション上でのKubernetesコマンドラインツールのインストール

The cluster startup script will leave you with a running cluster and a kubernetes directory on your workstation.

The kubectl tool controls the Kubernetes cluster manager. It lets you inspect your cluster resources, create, delete, and update components, and much more. You will use it to look at your new cluster and bring up example apps.

You can use gcloud to install the kubectl command-line tool on your workstation:

gcloud components install kubectl
備考: The kubectl version bundled with gcloud may be older than the one downloaded by the get.k8s.io install script. See Installing kubectl document to see how you can set up the latest kubectl on your workstation.

クラスターの始まり

クラスターの様子を見る

Once kubectl is in your path, you can use it to look at your cluster. E.g., running:

kubectl get --all-namespaces services

should show a set of services that look something like this:

NAMESPACE     NAME          TYPE             CLUSTER_IP       EXTERNAL_IP       PORT(S)        AGE
default       kubernetes    ClusterIP        10.0.0.1         <none>            443/TCP        1d
kube-system   kube-dns      ClusterIP        10.0.0.2         <none>            53/TCP,53/UDP  1d
kube-system   kube-ui       ClusterIP        10.0.0.3         <none>            80/TCP         1d
...

Similarly, you can take a look at the set of pods that were created during cluster startup. You can do this via the

kubectl get --all-namespaces pods

command.

You’ll see a list of pods that looks something like this (the name specifics will be different):

NAMESPACE     NAME                                           READY     STATUS    RESTARTS   AGE
kube-system   coredns-5f4fbb68df-mc8z8                       1/1       Running   0          15m
kube-system   fluentd-cloud-logging-kubernetes-minion-63uo   1/1       Running   0          14m
kube-system   fluentd-cloud-logging-kubernetes-minion-c1n9   1/1       Running   0          14m
kube-system   fluentd-cloud-logging-kubernetes-minion-c4og   1/1       Running   0          14m
kube-system   fluentd-cloud-logging-kubernetes-minion-ngua   1/1       Running   0          14m
kube-system   kube-ui-v1-curt1                               1/1       Running   0          15m
kube-system   monitoring-heapster-v5-ex4u3                   1/1       Running   1          15m
kube-system   monitoring-influx-grafana-v1-piled             2/2       Running   0          15m

Some of the pods may take a few seconds to start up (during this time they’ll show Pending), but check that they all show as Running after a short period.

いくつかの例の実行

Then, see a simple nginx example to try out your new cluster.

For more complete applications, please look in the examples directory. The guestbook example is a good “getting started” walkthrough.

クラスターの解体

To remove/delete/teardown the cluster, use the kube-down.sh script.

cd kubernetes
cluster/kube-down.sh

Likewise, the kube-up.sh in the same directory will bring it back up. You do not need to rerun the curl or wget command: everything needed to setup the Kubernetes cluster is now on your workstation.

カスタマイズ

The script above relies on Google Storage to stage the Kubernetes release. It then will start (by default) a single master VM along with 3 worker VMs. You can tweak some of these parameters by editing kubernetes/cluster/gce/config-default.sh You can view a transcript of a successful cluster creation here.

トラブルシューティング

プロジェクトの設定

You need to have the Google Cloud Storage API, and the Google Cloud Storage JSON API enabled. It is activated by default for new projects. Otherwise, it can be done in the Google Cloud Console. See the Google Cloud Storage JSON API Overview for more details.

Also ensure that– as listed in the Prerequisites section– you’ve enabled the Compute Engine Instance Group Manager API, and can start up a GCE VM from the command line as in the GCE Quickstart instructions.

クラスター初期化のハング

If the Kubernetes startup script hangs waiting for the API to be reachable, you can troubleshoot by SSHing into the master and node VMs and looking at logs such as /var/log/startupscript.log.

Once you fix the issue, you should run kube-down.sh to cleanup after the partial cluster creation, before running kube-up.sh to try again.

SSH

If you’re having trouble SSHing into your instances, ensure the GCE firewall isn’t blocking port 22 to your VMs. By default, this should work but if you have edited firewall rules or created a new non-default network, you’ll need to expose it: gcloud compute firewall-rules create default-ssh --network=<network-name> --description "SSH allowed from anywhere" --allow tcp:22

Additionally, your GCE SSH key must either have no passcode or you need to be using ssh-agent.

ネットワーク

The instances must be able to connect to each other using their private IP. The script uses the “default” network which should have a firewall rule called “default-allow-internal” which allows traffic on any port on the private IPs. If this rule is missing from the default network or if you change the network being used in cluster/config-default.sh create a new rule with the following field values:

  • Source Ranges: 10.0.0.0/8
  • Allowed Protocols and Port: tcp:1-65535;udp:1-65535;icmp

サポートレベル

IaaS ProviderConfig. MgmtOSNetworkingDocsConformsSupport Level
GCESaltstackDebianGCEdocsProject

参考文献

Please see the Kubernetes docs for more details on administering and using a Kubernetes cluster.

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