I am trying to clone a private git repository(gitLab) into a kubernetes pod, using SSH keys for authentication. I have stored my keys in a secret. Here is the yaml file for the job that does the desired task.

Heres the same question, but doesnt give the exact solution :

Clone a secure git repo in Kubernetes pod

Logs of the init container after execution:

fetch http://dl-cdn.alpinelinux.org/alpine/v3.7/main/x86_64/APKINDEX.tar.gz
fetch http://dl-cdn.alpinelinux.org/alpine/v3.7/community/x86_64/APKINDEX.tar.gz
v3.7.1-66-gfc22ab4fd3 [http://dl-cdn.alpinelinux.org/alpine/v3.7/main]
v3.7.1-55-g7d5f104fa7 [http://dl-cdn.alpinelinux.org/alpine/v3.7/community]
OK: 9064 distinct packages available
OK: 23 MiB in 23 packages
Cloning into '/tmp'...
Host key verification failed.
fatal: Could not read from remote repository.

Please make sure you have the correct access rights
and the repository exists.

The yaml file which works perfectly for public repo:

apiVersion: batch/v1
kind: Job
metadata:
  name: nest-build-kaniko
  labels:
    app: nest-kaniko-example
spec:
  template:
    spec:
      containers:
        -
          image: 'gcr.io/kaniko-project/executor:latest'
          name: kaniko
          args: ["--dockerfile=/workspace/Dockerfile",
                "--context=/workspace/",
                "--destination=aws.dest.cred"]
          volumeMounts:
            -
              mountPath: /workspace
              name: source
            -
              name: aws-secret
              mountPath: /root/.aws/
            -
              name: docker-config
              mountPath: /kaniko/.docker/
      initContainers:
        -
          name: download
          image: alpine:3.7
          command: ["/bin/sh","-c"]
          args: ['apk add --no-cache git && git clone https://github.com/username/repo.git /tmp/']
          volumeMounts:
            -
              mountPath: /tmp
              name: source
      restartPolicy: Never
      volumes:
        -
          emptyDir: {}
          name: source
        -
          name: aws-secret
          secret:
            secretName: aws-secret
        -
          name: docker-config
          configMap:
            name: docker-config

The yaml file after using git-sync for cloning private repository:

apiVersion: batch/v1
kind: Job
metadata:
  name: nest-build-kaniko
  labels:
    app: nest-kaniko-example
spec:
  template:
    spec:
      containers:
        -
          image: 'gcr.io/kaniko-project/executor:latest'
          name: kaniko
          args: ["--dockerfile=/workspace/Dockerfile",
                "--context=/workspace/",
                "--destination=aws.dest.cred"]
          volumeMounts:
            -
              mountPath: /workspace
              name: source
            -
              name: aws-secret
              mountPath: /root/.aws/
            -
              name: docker-config
              mountPath: /kaniko/.docker/
      initContainers:
        -
          name: git-sync
          image: gcr.io/google_containers/git-sync-amd64:v2.0.4
          volumeMounts:
            -
              mountPath: /git/tmp
              name: source
            -
              name: git-secret
              mountPath: "/etc/git-secret"
          env:
            - name: GIT_SYNC_REPO
              value: "git@gitlab.com:username/repo.git"
            - name: GIT_SYNC_SSH
              value: "true"
            - name: GIT_SYNC_DEST
              value: "/tmp"
            - name: GIT_SYNC_ONE_TIME
              value: "true"
          securityContext:
            runAsUser: 0
      restartPolicy: Never
      volumes:
        -
          emptyDir: {}
          name: source
        -
          name: aws-secret
          secret:
            secretName: aws-secret
        -
          name: git-secret
          secret:
            secretName: git-creds
            defaultMode: 256
        -
          name: docker-config
          configMap:
            name: docker-config