If you have a python file: myfunction.py
def hours_to_minutes(minutes): hours = minutes / 60.0 return hours <span data-mce-type="bookmark" id="mce_SELREST_start" data-mce-style="overflow:hidden;line-height:0" style="overflow:hidden;line-height:0" ></span>
Then you can execute it with:
python -c ‘from function import *; print(hours_to_minutes(20))’
KUBELET
This is the first and most important component in Kubernetes. Kubelet’s responsibility is to spawn/kill pods and containers on its node, it communicates directly with Docker daemon so we need to install it first. For Ubuntu 16.04 the default version of Docker is 1.12.6.
root@node:~$ apt-get update && apt-get install -y docker.io root@node:~$ docker version Client: Version: 1.12.6 API version: 1.24 Go version: go1.6.2 Git commit: 78d1802 Built: Tue Jan 31 23:35:14 2017 OS/Arch: linux/amd64 Server: Version: 1.12.6 API version: 1.24 Go version: go1.6.2 Git commit: 78d1802 Built: Tue Jan 31 23:35:14 2017 OS/Arch: linux/amd64
So let’s download Kubernetes binaries and run kubelet.
root@node:~$ wget -q --show-progress https://dl.k8s.io/v1.7.6/kubernetes-server-linux-amd64.tar.gz kubernetes-server-linux-amd64.tar.gz 100%[==================================================================================================================================>] 417.16M 83.0MB/s in 5.1s root@node:~$ tar xzf kubernetes-server-linux-amd64.tar.gz root@node:~$ mv kubernetes/server/bin/* /usr/local/bin/ root@node:~$ rm -rf *
We run kubelet with –pod-manifest-path option. This is the directory that kubelet will watch for pod manifest yaml files.
root@node:~$ kubelet --pod-manifest-path /tmp/manifests &> /tmp/kubelet.log &
Let’s put simple nginx pod manifest file to that directory and see what happens.
apiVersion: v1 kind: Pod metadata: name: nginx labels: app: nginx spec: containers: - name: nginx image: nginx ports: - containerPort: 80
Now we can check docker ps to see that our container has been added and try to curl it:
root@node:~$ docker ps CONTAINER ID IMAGE COMMAND CREATED STATUS PORTS NAMES c3369c72ebb2 nginx@sha256:aa1c5b5f864508ef5ad472c45c8d3b6ba34e5c0fb34aaea24acf4b0cee33187e "nginx -g 'daemon off" 3 minutes ago Up 3 minutes k8s_nginx_nginx-node_default_594710e736bc86ef2c87ea5615da08b1_0 b603d65d8bfd gcr.io/google_containers/pause-amd64:3.0 "/pause" 3 minutes ago Up 3 minutes k8s_POD_nginx-node_default_594710e736bc86ef2c87ea5615da08b1_0 root@node:~$ docker inspect b603d65d8bfd | jq .[0].NetworkSettings.IPAddress "172.17.0.2" root@node:~$ curl 172.17.0.2 <!DOCTYPE html> <html> <head> <title>Welcome to nginx!</title>
The b603d65d8bfd is the id of a pause container. This is an infrastructure container that Kubernetes creates first when creating a pod. Using a pause container Kubernetes acquires IP and setup network namespace. All other containers in a pod shares the same IP address and network interface. When all your containers die, this is the last container that holds whole network namespace.
This is how our node looks like now:
KUBE API SERVER
Kubernetes use etcd, a distributed database with strong consistency data model to store the state of whole cluster. API Server is the only component that can talk to etcd directly, all other components (including kubelet) have to communicate through API Server. Let’s try to run API Server with kubelet.
First we need etcd:
root@node:~$ wget -q --show-progress https://github.com/coreos/etcd/releases/download/v3.2.6/etcd-v3.2.6-linux-amd64.tar.gz etcd-v3.2.6-linux-amd64.tar.gz 100%[==================================================================================================================================>] 9.70M 2.39MB/s in 4.1s root@node:~$ tar xzf etcd-v3.2.6-linux-amd64.tar.gz root@node:~$ mv etcd-v3.2.6-linux-amd64/etcd* /usr/local/bin/ root@node:~$ etcd --listen-client-urls http://0.0.0.0:2379 --advertise-client-urls http://localhost:2379 &> /tmp/etcd.log & root@node:~$ etcdctl cluster-health member 8e9e05c52164694d is healthy: got healthy result from http://46.101.177.76:2379 cluster is health
And the API Server:
root@node:~$ kube-apiserver --etcd-servers=http://localhost:2379 --service-cluster-ip-range=10.0.0.0/16 --bind-address=0.0.0.0 --insecure-bind-address=0.0.0.0 &> /tmp/apiserver.log &
root@node:~$ curl http://localhost:8080/api/v1/nodes
{
"kind": "NodeList",
"apiVersion": "v1",
"metadata": {
"selfLink": "/api/v1/nodes",
"resourceVersion": "45"
},
"items": []
}
Now we can connect kubelet to API Server and check if it was discovered by the cluster.
root@node:~$ pkill -f kubelet root@node:~$ kubelet --api-servers=localhost:8080 &> /tmp/kubelet.log & root@node:~$ kubectl get nodes NAME STATUS AGE VERSION node Ready 5m v1.7.6 root@node:~$ kubectl get pods No resources found.
We don’t have any pods yet, so let’s create one with kubectl create -f nginx.yaml using previous manifest file.
root@node:~$ kubectl create -f nginx.yaml pod "nginx" created root@node:~$ kubectl get pods NAME READY STATUS RESTARTS AGE nginx 0/1 Pending 0 6m
Notice here that the pod hangs in Pending status – but why ? This is because we don’t yet have another Kubernetes component responsible for choosing a node for the pod – Scheduler. We will talk about it later but for now we can just create nginx2 with updated manifest that determinates what node should be used.
root@node:~# git diff nginx.yaml nginx2.yaml diff --git a/nginx.yaml b/nginx2.yaml index 7053af0..36885ae 100644 --- a/nginx.yaml +++ b/nginx2.yaml @@ -1,10 +1,11 @@ apiVersion: v1 kind: Pod metadata: - name: nginx + name: nginx2 labels: app: nginx spec: + nodeName: node containers: - name: nginx image: nginx root@node:~$ kubectl create -f nginx2.yaml root@node:~$ kubectl get pod NAME READY STATUS RESTARTS AGE nginx 0/1 Pending 0 10m nginx2 1/1 Running 0 8s
Great, so now we can see that API Server and kubelet works. This is how our node looks like now:
KUBE SCHEDULER
Scheduler is responsible for assigning pod to a node. It watches pods and assigns available nodes to those without one.
We still have nginx pod that is in Pending state from previous example. Let’s run scheduler and see what happens.
root@node:~$ kube-scheduler --master=http://localhost:8080 &> /tmp/scheduler.log & root@node:~$ kubectl get pods NAME READY STATUS RESTARTS AGE nginx 1/1 Running 0 17m nginx2 1/1 Running 0 17m view raw10.sh hosted with by GitHub as you can see the scheduler kicks in, finds a pod and assigns it to the node. You can see it’s placement on our node schema: KUBE CONTROLLER MANAGER Controller Manager is responsible for managing (among others) Replication Controllers and Replica Sets so without it we can’t use Kubernetes Deployments. Here we are going to run it and create a deployment. apiVersion: apps/v1beta1 kind: Deployment metadata: name: nginx spec: replicas: 3 template: metadata: labels: run: nginx spec: containers: - name: nginx image: nginx ports: - containerPort: 80 view rawnginx-deploy.yaml hosted with by GitHub root@node:~$ kube-controller-manager --master=http://localhost:8080 &> /tmp/controller-manager.log & root@node:~$ kubectl create -f nginx-deploy.yaml deployment "nginx" created root@node:~$ kubectl get deploy NAME DESIRED CURRENT UP-TO-DATE AVAILABLE AGE nginx 3 3 3 2 7s root@node:~$ kubectl get po NAME READY STATUS RESTARTS AGE nginx 1/1 Running 0 32m nginx-31893996-3dnx7 1/1 Running 0 18s nginx-31893996-5d1ts 1/1 Running 0 18s nginx-31893996-9k93w 1/1 Running 0 18s nginx2 1/1 Running 0 32m
Updated version of our node scheme:
KUBE PROXY
Kubernetes (network) proxy is responsible for managing Kubernetes Services and thus internal load balancing and exposing pods internally for other pods and for external clients.
apiVersion: v1 kind: Service metadata: name: nginx labels: run: nginx spec: type: NodePort ports: - name: http port: 80 nodePort: 30073 selector: run: nginx root@node:~$ kube-proxy --master=http://localhost:8080 &> /tmp/proxy.log & root@node:~$ kubectl create -f nginx-svc.yaml service "nginx" created root@node:~$ kubectl get svc NAME CLUSTER-IP EXTERNAL-IP PORT(S) AGE kubernetes 10.0.0.1 <none> 443/TCP 2h nginx 10.0.167.201 <nodes> 80:30073/TCP 7s view raw2-12.sh hosted with by GitHub Nginx deployment is now exposed via 30073 port externally, we can check that with curl. $ doctl compute droplet list (env: st) ID Name Public IPv4 Private IPv4 Public IPv6 Memory VCPUs Disk Region Image Status Tags 63370004 node1 46.101.177.76 10.135.53.41 2048 2 40 fra1 Ubuntu 16.04.3 x64 active $ curl http://46.101.177.76:30073 <!DOCTYPE html> <html> <head> <title>Welcome to nginx!</title>
Edit .bashrc in your home directory and add the following line:
export PATH="/path/to/dir:$PATH"
You will need to source your .bashrc or logout/login (or restart the terminal) for the changes to take effect. To source your .bashrc, simply type
$ source ~/.bashrcI am concerned about pushing information such as passwords or IP addresses into remote Git repositories. Can I avoid this e.g. by making use of environment variables, e.g. with a deployment spec and actual deployment roughly as follows:
spec:
type: LoadBalancer
loadBalancerIP: ${SERVICE_ADDRESS}
and
export SERVICE_ADDRESS=<static-ip-address>
kubectl create -f Deployment.yaml
Obviously this specific syntax does not work yet. But is something like this possible and if so how?
Solution:
In deploy.yml:
LoadbalancerIP: $LBIP
Then just create your env var and run kubectl like this:
export LBIP="1.2.3.4" envsubst < deploy.yml | kubectl apply -f -envsubstis available in e.g. Ubuntu/Debiangettextpackage.
This issue is mainly with Java version or Maven version.
You can add Java version in the Manage Jenkins -> Tool configuration section as:
JDK -> JDK installations
Then you can choose the required java in the job as follows:
To change Maven:
1. First download maven from: https://maven.apache.org/download.cgi
2. Unzip it in a directory accessible by Jenkins suppose: /home/jenkins/apache-maven-3.2.3
3. Then add maven as
You can also add mvn to PATH and manually execute mvn clean for that project.
Well, ‘Loaded all jobs’ is not the last init stage, ‘Completed’ is. So there appears to be a problem
Do you have the extremenotification plugin installed? It’s the one referenced in JENKINS-37759.
#! /bin/bash
SAVEIFS=$IFS
IFS=$(echo -en "\n\b")
declare -i
for i in $(java -jar jenkins-cli.jar -s http://localhost:8080 list-jobs --username admin --password admin123);
do
echo $i;
java -jar jenkins-cli.jar -s http://localhost:8080 get-job --username admin --password admin123 ${i} > backup/${i}.xml;
echo "done";
done
