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Using SSH with git-sync

Git-sync supports using the SSH protocol for pulling git content.

Step 1: Create Secret

Create a Secret to store your SSH private key, with the Secret keyed as "ssh". This can be done one of two ways:

Method 1:

Obtain the host keys for your git server:

ssh-keyscan $YOUR_GIT_HOST > /tmp/known_hosts

Use the kubectl create secret command and point to the file on your filesystem that stores the key. Ensure that the file is mapped to "ssh" as shown (the file can be located anywhere).

kubectl create secret generic git-creds \
    --from-file=ssh=$HOME/.ssh/id_rsa \
    --from-file=known_hosts=/tmp/known_hosts

Method 2:

Write a config file for a Secret that holds your SSH private key, with the key (pasted in base64 encoded plaintext) mapped to the "ssh" field.

{
  "kind": "Secret",
  "apiVersion": "v1",
  "metadata": {
    "name": "git-creds"
  },
  "data": {
    "ssh": <base64 encoded private-key>
    "known_hosts": <base64 encoded known_hosts>
  }
}

Create the Secret using kubectl create -f.

kubectl create -f /path/to/secret-config.json

Step 2: Configure Pod/Deployment volume

In your Pod or Deployment configuration, specify a volume for mounting the Secret. Ensure that secretName matches the name you used when creating the Secret (e.g. "git-creds" used in both above examples).

      # ...
      volumes:
      - name: git-secret
        secret:
          secretName: git-creds
          defaultMode: 0400
      # ...

Step 3: Configure git-sync container

In your git-sync container configuration, mount the Secret volume at "/etc/git-secret". Ensure that the --repo flag (or the GITSYNC_REPO environment variable) is set to use the SSH protocol (e.g. git@github.com/foo/bar). You will also need to set your container's securityContext to run as user ID "65533" which is created for running git-sync as non-root.

      # ...
      containers:
      - name: git-sync
        image: registry.k8s.io/git-sync/git-sync:v4.2.4
        args:
         - "--repo=git@github.com:foo/bar"
         - "--link=bar"
        volumeMounts:
        - name: git-secret
          mountPath: /etc/git-secret
        securityContext:
          runAsUser: 65533 # git-sync user
      # ...

Lastly, you need to tell your Pod to run with the git-sync FS group. Note that this is a Pod-wide setting, unlike the container securityContext above.

      # ...
      securityContext:
        fsGroup: 65533 # to make SSH key readable
      # ...

If you want git-sync to run as a different (non-root) UID and GID, you can change these last blocks to any UID/GID you like. SSH demands that the current UID be present in /etc/passwd, so in this case you will need to add the --add-user flag to git-sync's args array.

Note: Kubernetes mounts the Secret with permissions 0444 by default (not restrictive enough to be used as an SSH key), so make sure you set the defaultMode.

Full example

In case the above YAML snippets are confusing (because whitespace matters in YAML), here is a full example:

apiVersion: apps/v1
kind: Deployment
metadata:
  name: git-sync
spec:
  selector:
    matchLabels:
      demo: git-sync
  template:
    metadata:
      labels:
        demo: git-sync
    spec:
      volumes:
      - name: git-secret
        secret:
          secretName: git-creds
          defaultMode: 0400
      containers:
      - name: git-sync
        image: registry.k8s.io/git-sync/git-sync:v4.2.4
        args:
         - "--repo=git@github.com:torvalds/linux"
         - "--depth=1"
        securityContext:
          runAsUser: 65533 # git-sync user
        volumeMounts:
        - name: git-secret
          mountPath: /etc/git-secret
          readOnly: true
      securityContext:
        fsGroup: 65533 # to make SSH key readable