CODEWITHSUNDEEP
kubernetes
Shahar Hamuzim Rajuan
Shahar Hamuzim Rajuan

Reputation: 6129

Running a shell script to initialize pods in kubernetes (initializing my db cluster)

I need to be able to run a shell script (my script is for initializing my db cluster) to initialize my pods in Kubernetes,

I don't want to create my script inside my dockerfile because I get my image directly from the web so I don't want to touch it.

So I want to know if there is a way to get my script in to one of my volumes so I can execute it like that:

spec:
  containers:
  - name: command-demo-container
    image: debian
    command: ["./init.sh"]
  restartPolicy: OnFailure

Upvotes: 5

Views: 14378

Answers (2)

Shahar Hamuzim Rajuan
Shahar Hamuzim Rajuan

Reputation: 6129

I finally decided to take the approach of creating a config file with the script we want to run and then call this configMap from inside the volume.

this is a short explanation:

In my pod.yaml file there is a VolumeMount called "/pgconf" which is the directory that the docker image reads any SQL script that you put there and run it when the pod is starting. And inside Volumes I will put the configMap name (postgres-init-script-configmap) which is the name of the config defined inside the configmap.yaml file.

There is no need to create the configMap using kubernetes, The pod will take the configuration from the configMap file as long as you place it in the same directory as the pod.yaml .

my POD yaml file:

apiVersion: v1
kind: Pod
metadata:
  name: "{{.Values.container.name.primary}}"
  labels:
    name: "{{.Values.container.name.primary}}"
spec:
  securityContext:
    fsGroup: 26
  restartPolicy: {{default "Always" .Values.restartPolicy}}

  containers:
  - name: {{.Values.container.name.primary}}
    image: "{{.Values.image.repository}}/{{.Values.image.container}}:{{.Values.image.tag}}"
    ports:
    - containerPort: {{.Values.container.port}}
    env:
    - name: PGHOST
      value: /tmp
    - name: PG_PRIMARY_USER
      value: primaryuser
    - name: PG_MODE
      value: primary
    resources:
      requests:
        cpu: {{ .Values.resources.cpu }}
        memory: {{ .Values.resources.memory }}
    volumeMounts:
    - mountPath: /pgconf
      name: init-script
      readOnly: true
  volumes:
  - name: init-script
    configMap:
      name: postgres-init-script-configmap

my configmap.yaml (Which contains the SQL script that will initial the DB):

apiVersion: v1
kind: ConfigMap
metadata:
  name: postgres-init-script-configmap
data:
  setup.sql: |-
    CREATE USER david WITH PASSWORD 'david';

Upvotes: 2

Jakub
Jakub

Reputation: 4006

It depends what exactly does your init script do. But the InitContainers should be helpful in such cases. Init containers are run before the main application container is started and can do some preparation work such as create configuration files etc.

You would still need your own Docker image, but it doesn't have to be the same image as the database one.

Upvotes: 2

Related Questions