example of init containers

deployment.yaml

apiVersion: extensions/v1beta1
kind: Deployment
metadata:
  name: my-app
spec:
  replicas: 1
  template:
    metadata:
      labels:
        app: my-app
    spec:
      containers:
        - name: my-app-container
          resources:
            limits:
              cpu: 200m
              memory: 200Mi
          image: mhart/alpine-node:10.11.0
          ports:
            - containerPort: 5000
          env:
            - name: NODE_ENV
              value: production
            - name: NPM_CONFIG_LOGLEVEL
              value: warn
          command: ["/bin/sh"]
          args: ["-c", "cd /var/www/app; yarn start"]
          volumeMounts:
            - name: git-repo
              mountPath: /var/www/app
      initContainers:
        - name: init-git
          image: alpine/git
          env:
            - name: GH_TOKEN
              valueFrom:
                secretKeyRef:
                  name: github-token-secret
                  key: GH_TOKEN
          args:
            - clone
            - --single-branch
            - --
            - https://$(GH_TOKEN)@github.com/yourorganization/yourapp.git
            - /var/www/app
          volumeMounts:
            - name: git-repo
              mountPath: /var/www/app
        - name: init-yarn
          image: mhart/alpine-node:10.11.0
          env:
            - name: NODE_ENV
              value: production
            - name: NPM_CONFIG_LOGLEVEL
              value: warn
            - name: NPM_TOKEN
              valueFrom:
                secretKeyRef:
                  name: npm-token-secret
                  key: NPM_TOKEN
          command: ["/bin/sh"]
          args:
            [
              "-c",
              "cd /var/www/app; echo \\/\\/registry.npmjs.org\\/:_authToken=$(NPM_TOKEN) > .npmrc; yarn install; rm .npmrc;",
            ]
          volumeMounts:
            - name: git-repo
              mountPath: /var/www/app
      volumes:
        - name: git-repo
          emptyDir: {}