Mount Propogation not working as expected(/var, /var:shared and /mnt/s3data are not in sync)

[Sud369]

    command: ["./goofys", "-f", "mybucket3", "/var"]
    securityContext:
      privileged: true
    volumeMounts:
    - name: s3data
      mountPath: /var:shared
    env:
      - name: S3_BUCKET
        value: mybucket3
      - name: MOUNT_PATH
        value: /var
  volumes:
  - name: s3data
    hostPath:
      path: /mnt/s3data

===========================================================
With the following lines in daemonset.yaml
/var is mounted with s3 (i.e. changes made in s3 is reflected in /var folder in container and vice versa)
/var:shared is mounted with /mnt/s3data (i.e changes made in /var:shared folder in container is reflected in host and vv)
However /var , /var:shared and s3 bucket is not in sync.
Probably mount Propagation is not working as expected.
Kindly suggest in case of any suggestion or possible workarounds/solutions.

[renierwoo]

Hi!

I have experienced the same behavior but with the mountpoint-s3 application (from awslabs). I was able to get it working by doing the following:

[DaemonSet]
...
spec:
  containers:
    - name: <example.app>
       image: <example.repo>
       command:
          - '/bin/sh'
          - '-c'
       args:
          - |
            mkdir -p /var/s3data/bucket && /mount-s3 -f --auto-unmount <example.bucket> /var/s3data/bucket
       volumeMounts:
         - name: mys3data
           mountPath: /var/s3data
           mountPropagation: Bidirectional
       securityContext:
         privileged: true
         capabilities:
           add:
           - SYS_ADMIN
  volumes:
    - name: mys3data
       hostPath:
         path: /mnt/mys3data
  serviceAccount: example.serviceAccount
...

You should try making a mount point in /var (the directory that will map to the host directory /mnt/s3data) without using :shared. In the command section, first generate the directory where the s3 bucket will be mounted, which must be inside /var (e.g /var/bucket) because when the daemonset makes the mount point /var it overlaps the content from /var folder inside the container . In the section volumeMounts you need to add mountPropagation: Bidirectional to convey with Mount Propagation by Kubernetes

So I think if you can translate it to your scenario, maybe it will work for you.