OpenShift Container Platform

Create Init Containers

You create an init container by creating a pod spec that contains an initContainers configuration.

The following example outlines a simple pod which has two init containers. The first init continer waits for the myservice service to complete. After that, the second waits for mydb service to complete. After both init containers complete, the pod begins.

Procedure

Create the pod for the Init Container:

Create a YAML file similar to the following:

apiVersion: v1
kind: Pod
metadata:
  name: myapp-pod
  labels:
    app: myapp
spec:
  securityContext:
    runAsNonRoot: true
    seccompProfile:
      type: RuntimeDefault
  containers:
  - name: myapp-container
    image: registry.access.redhat.com/ubi9/ubi:latest
    command: ['sh', '-c', 'echo The app is running! && sleep 3600']
    securityContext:
      allowPrivilegeEscalation: false
      capabilities:
        drop: [ALL]
  initContainers:
  - name: init-myservice
    image: registry.access.redhat.com/ubi9/ubi:latest
    command: ['sh', '-c', 'until getent hosts myservice; do echo waiting for myservice; sleep 2; done;']
    securityContext:
      allowPrivilegeEscalation: false
      capabilities:
        drop: [ALL]
  - name: init-mydb
    image: registry.access.redhat.com/ubi9/ubi:latest
    command: ['sh', '-c', 'until getent hosts mydb; do echo waiting for mydb; sleep 2; done;']
    securityContext:
      allowPrivilegeEscalation: false
      capabilities:
        drop: [ALL]

Create the pod by using the following command:
```
$ oc create -f myapp.yaml
```

View the status of the pod by using the following command:

$ oc get pods

Example output

NAME                          READY     STATUS              RESTARTS   AGE
myapp-pod                     0/1       Init:0/2            0          5s

The pod status, Init:0/2, indicates it is waiting for the two services.

Create the myservice service.

Create a YAML file similar to the following:

kind: Service
apiVersion: v1
metadata:
  name: myservice
spec:
  ports:
  - protocol: TCP
    port: 80
    targetPort: 9376

Create the pod by using the following command:
```
$ oc create -f myservice.yaml
```
View the status of the pod by using the following command:
```
$ oc get pods
```
Example output
```
NAME                          READY     STATUS              RESTARTS   AGE
myapp-pod                     0/1       Init:1/2            0          5s
```
The pod status, Init:1/2, indicates it is waiting for one service, in this case the mydb service.

Create the mydb service:

Create a YAML file similar to the following:

kind: Service
apiVersion: v1
metadata:
  name: mydb
spec:
  ports:
  - protocol: TCP
    port: 80
    targetPort: 9377

Create the pod by using the following command:
```
$ oc create -f mydb.yaml
```
View the status of the pod by using the following command:
```
$ oc get pods
```
Example output
```
NAME                          READY     STATUS              RESTARTS   AGE
myapp-pod                     1/1       Running             0          2m
```
The pod status, Running, indicates that it is no longer waiting for the services and is running.