Kubernetes 从入门到进阶 第一个Helloworld程序
本文将使用kubernetes-ansible进行安装，由于其kubernetes-ansible更新很快，细小的地方又发生了一定变化，简单记录一下，同时由于特殊原因，一般网内用户都无法正常运行k8s。所以这个系列准备写一些咱们自己能用的例子来学习k8s的基础知识。
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本文将使用kubernetes-ansible进行安装，由于其kubernetes-ansible更新很快，细小的地方又发生了一定变化，简单记录一下，同时由于特殊原因，一般网内用户都无法正常运行k8s。所以这个系列准备写一些咱们自己能用的例子来学习k8s的基础知识。
构成说明
演示程序使用下列的集群构成。
| No | type | IP | OS |
|---|---|---|---|
| 1 | master | 192.168.32.131 | CENTOS7.2 |
| 2 | etcd | 192.168.32.131 | CENTOS7.2 |
| 3 | minion | 192.168.32.132 | CENTOS7.2 |
| 3 | minion | 192.168.32.133 | CENTOS7.2 |
| 3 | minion | 192.168.32.134 | CENTOS7.2 |
Step 1：安装ansible
在192.168.32.131上安装ansible
[root@host131 local]# yum -y install epel-release
[root@host131 local]# yum -y install ansible确认安装
[root@host131 local]# ansible --version
ansible 2.1.0.0
config file = /etc/ansible/ansible.cfg
configured module search path = Default w/o overrides
[root@host131 local]#Step 2：设定ssh通路和ansible
分别在4台机器上生成ssh的key
设定4台机器的/etc/hosts
设定4台机器ssh通路
在ansible所安装的机器上，追加机器信息到/etc/ansible/hosts中
确认ansible正常动作
Step 3：下载contrib
[root@host31 local]# cd ..
[root@host31 /]# mkdir -p /local; cd /local
[root@host131 local]# git clone https://github.com/kubernetes/contrib
Cloning into 'contrib'...
remote: Counting objects: 30938, done.
remote: Compressing objects: 100% (31/31), done.
remote: Total 30938 (delta 12), reused 0 (delta 0), pack-reused 30907
Receiving objects: 100% (30938/30938), 32.69 MiB | 153.00 KiB/s, done.
Resolving deltas: 100% (14922/14922), done.
Checking out files: 100% (16114/16114), done.
[root@host131 local]#Step 4：生成kubernetes-ansible设定文件
按照构成说明中的4台机器构成，设定inventory文件
[root@host131 inventory]# pwd
/local/contrib/ansible/inventory
[root@host131 inventory]# ll
total 4
drwxr-xr-x. 2 root root 20 Aug 29 20:06 group_vars
-rw-r--r--. 1 root root 132 Aug 29 20:06 localhost.ini
[root@host131 inventory]# cp localhost.ini inventory
[root@host131 inventory]# vi inventory
[root@host131 inventory]# cat inventory
[masters]
host131
[nodes]
host132
host133
host134
[etcd]
host131
[root@host131 inventory]#设定inventory/group_vars/all.yml，将kube-ui打开，从default的false该为true
85 # Turn to false to disable the kube-ui addon for this cluster
86 kube-ui: false
Step 6：安装所需package
依赖关系整理的真不错，只有一个package在github的说明中虽然没有提到，但是实际是需要提前安装的
| No | package | 机器 | 安装命令 |
|---|---|---|---|
| 1 | python-netaddr | 192.168.32.131 | yum -y install python-netaddr |
Step 7：执行安装文件
执行安装文件deploy-cluster.sh
[root@host131 ansible]# pwd
/local/contrib/ansible
[root@host131 ansible]# cd scripts/ && ./deploy-cluster.shStep 8：确认kubernetes
确认node
确认services
确认版本
[root@host131 scripts]# kubectl version
Client Version: version.Info{Major:"1", Minor:"2", GitVersion:"v1.2.0", GitCommit:"ec7364b6e3b155e78086018aa644057edbe196e5", GitTreeState:"clean"}
Server Version: version.Info{Major:"1", Minor:"2", GitVersion:"v1.2.0", GitCommit:"ec7364b6e3b155e78086018aa644057edbe196e5", GitTreeState:"clean"}
[root@host131 scripts]#
[root@host131 scripts]# kubectl get nodes
NAME STATUS AGE
host132 Ready 2m
host133 Ready 2m
host134 Ready 2m
[root@host131 scripts]# kubectl get service
NAME CLUSTER-IP EXTERNAL-IP PORT(S) AGE
kubernetes 10.254.0.1 <none> 443/TCP 12m
[root@host131 scripts]#Hello world示例
事前准备
因为pod在创建的时候会用到一个helper的镜像，以前叫pause-amd64，在k8s1.2之后都是叫做pause，因为它需要从gcr.io下载，所以大部分用户都无法下载，所以pod的状态会一直是ContainerCreating。我把这个放到一个docker用户都可以访问的地方，你也可以使用各种方法，只要取到对应的版本，将其部署到各个节点即可。在本文示例中，如下操作将在4个node都同样作一下。
[root@host131 ~]# docker search liumiaocn
INDEX NAME DESCRIPTION STARS OFFICIAL AUTOMATED
docker.io docker.io/liumiaocn/pause-amd64 gcr.io/google_containers/pause:2.0: Kubern... 0 [OK]
[root@host131 ~]# docker pull docker.io/liumiaocn/pause-amd64
Using default tag: latest
Trying to pull repository docker.io/liumiaocn/pause-amd64 ...
latest: Pulling from docker.io/liumiaocn/pause-amd64
8f216013977d: Pull complete
a3ed95caeb02: Pull complete
Digest: sha256:51dbbd8636156e778a30c9eaf481b6e751552aac4fc654795d58cdbfb516d25e
Status: Downloaded newer image for docker.io/liumiaocn/pause-amd64:latest
[root@host131 ~]# docker tag docker.io/liumiaocn/pause-amd64 gcr.io/google_containers/pause:2.0
[root@host131 ~]# docker images |grep 2.0
gcr.io/google_containers/pause 2.0 c5147e5f6708 Less than a second ago 350.2 kB
[root@host131 ~]#创建一个deployment
以前的RC现在逐渐会被deployment所替代，但是yml写法基本没有变法，不过cli的方式下有了明显的变化。用如下的命令创建一个运行起2个实例的redmine，端口为80。为了提高速度，可以事前在node的各节点将redmine的镜像提前pull下来。
kubectl run redminemgnt --image=redmine --replicas=2 --port=80确认结果
[root@host131 ~]# kubectl run redminemgnt --image=redmine --replicas=2 --port=80
deployment "redminemgnt" created
[root@host131 ~]# kubectl get pods
NAME READY STATUS RESTARTS AGE
redminemgnt-298222028-85fi9 1/1 Running 0 3m
redminemgnt-298222028-tfqi2 1/1 Running 0 3m
[root@host131 ~]# kubectl get deployment
NAME DESIRED CURRENT UP-TO-DATE AVAILABLE AGE
redminemgnt 2 2 2 2 4m
[root@host131 ~]#expose对外的port
export对外的port，以使得其他机器可以访问
[root@host131 ~]# kubectl expose deployment redminemgnt --port=80 --type=LoadBalancer
service "redminemgnt" exposed
[root@host131 ~]#确认2个实例如何启动在3个node上
通过如下可以看到，当我们把2个redmine的实例启动在3个node上的时候，k8s自动的进行的分配到了host133和host134，关于分配策略可以自己通过调整scale进行实验确认以加深理解。
[root@host131 ~]# kubectl get pods -o wide
NAME READY STATUS RESTARTS AGE NODE
redminemgnt-298222028-85fi9 1/1 Running 0 10m host134
redminemgnt-298222028-tfqi2 1/1 Running 0 10m host133
[root@host131 ~]#确认deploy
[root@host131 ~]# kubectl describe deployment redminemgnt
Name: redminemgnt
Namespace: default
CreationTimestamp: Tue, 30 Aug 2016 00:10:46 -0400
Labels: run=redminemgnt
Selector: run=redminemgnt
Replicas: 2 updated | 2 total | 2 available | 0 unavailable
StrategyType: RollingUpdate
MinReadySeconds: 0
RollingUpdateStrategy: 1 max unavailable, 1 max surge
OldReplicaSets: <none>
NewReplicaSet: redminemgnt-298222028 (2/2 replicas created)
Events:
FirstSeen LastSeen Count From SubobjectPath Type Reason Message
--------- -------- ----- ---- ------------- -------- ------ -------
13m 13m 1 {deployment-controller } Normal ScalingReplicaSet Scaled up replica set redminemgnt-298222028 to 2
[root@host131 ~]#确认pod
describe命令把各个组成部分清晰的列出来，所以对我们加深理解有很好的作用
[root@host131 ~]# kubectl describe pod redminemgnt-298222028-85fi9
Name: redminemgnt-298222028-85fi9
Namespace: default
Node: host134/192.168.32.134
Start Time: Tue, 30 Aug 2016 00:10:47 -0400
Labels: pod-template-hash=298222028,run=redminemgnt
Status: Running
IP: 172.16.64.4
Controllers: ReplicaSet/redminemgnt-298222028
Containers:
redminemgnt:
Container ID: docker://61e5320fc6877707c9cabeed8a272a41515d2a4ccf63f137d2eff760741e3865
Image: redmine
Image ID: docker://sha256:55ccd586ad119ceeb784ac924a15dd1060fa935beced3ce32e74967a0bc0ffac
Port: 80/TCP
QoS Tier:
cpu: BestEffort
memory: BestEffort
State: Running
Started: Tue, 30 Aug 2016 00:11:56 -0400
Ready: True
Restart Count: 0
Environment Variables:
Conditions:
Type Status
Ready True
Volumes:
default-token-8209b:
Type: Secret (a volume populated by a Secret)
SecretName: default-token-8209b
Events:
FirstSeen LastSeen Count From SubobjectPath Type Reason Message
--------- -------- ----- ---- ------------- -------- ------ -------
13m 13m 1 {default-scheduler } Normal Scheduled Successfully assigned redminemgnt-298222028-85fi9 to host134
12m 12m 1 {kubelet host134} spec.containers{redminemgnt} Normal Pulling pulling image "redmine"
12m 12m 1 {kubelet host134} spec.containers{redminemgnt} Normal Pulled Successfully pulled image "redmine"
12m 12m 1 {kubelet host134} spec.containers{redminemgnt} Normal Created Created container with docker id 61e5320fc687
12m 12m 1 {kubelet host134} spec.containers{redminemgnt} Normal Started Started container with docker id 61e5320fc687
[root@host131 ~]#这样第一个简单的kubernetes的Helloworld就完成了，接下我们会更加详细的学习k8s的其他基础知识。
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