[stable/minio] k8s mountPath and minio server root DIR should be decoupled

[gzur]

Problem statement
The minio Pod to only mounts the exact path that's passed to the minio executable, making it impossible to point to symlinks that lie outside of the minio bucket root.

It would be nice if the minio helm chart could show the symlink targets without exposing/traversing their location directly.

I was unable to achieve this using the current helm chart, since it uses a single variable ( .Values.mountPath ) for both the volumeMount and the DIR argument for the minio executable in deployment.yaml:

# simplified yaml
command:
   - minio server {{ .Values.mountPath }}" 
and
volumeMounts:
  {{- if and .Values.persistence.enabled [...] }}
  - name: export
    mountPath: {{ .Values.mountPath }}

Describe the solution you'd like
Unless I'm missing something obvious, I propose adding a variable named .Values.bucketRoot that defaults to the value of .Values.mountPath unless explicitly overridden.

• .Values.bucketRoot is passed to the minio executable as the DIR argument
• .Values.mountPath still being used to control the volumeMount

This will allow this behaviour to be configured without breaking backwards compatibility.

I also volunteer to create the PR.

Additional context
I was able to get this working by manually overriding templates/deployment.yaml so that it mounted /export/mnt into the pod while passing /export/mnt/data/ to the executable, which resulted in something like this:

mnt  <--- This gets mounted into the minio pod under `/export/mnt`
│
├── data  <--- This gets passed to the minio executable as `/export/mnt/data/`
│   ├── bucket1 ( contains symlinks to /mnt/volumes/ )
│   └── bucket2 ( contains symlinks to /mnt/volumes/ )
│
└── volumes <--- This is not accessible directly via minio, 
                 only indirectly through symlinks.

which worked like a charm.