feat(zfspv): mounting the root filesystem to remove the dependency on the Operating system (#204)

* feat(zfspv): mounting the root filesystem to remove the dependency on the OS

We are mounting the individual library to run the zfs
binary inside the ZFS-LocalPV daemonset. The problem with this
is each OS has different sets of libraries. We need to have different
Operator yamls for different OS versions.

Here we are mounting the root directory inside the ZFS-LocalPV daemonset Pod
which does chroot to this path and run the command. As all the libraries will
be available which are present on the host inside the Pod, so we don't need to mount each
library here and also it will work for all the Operating systems.

To be on the safe side, we are mounting the host's root directory
as Readonly filesystem.

Signed-off-by: Pawan <pawan@mayadata.io>

* adding comment for namespace

Signed-off-by: Pawan <pawan@mayadata.io>

deploy/zfs-operator.yaml

@@ -1531,6 +1531,24 @@ roleRef:
 
 ---
 
+kind: ConfigMap
+apiVersion: v1
+metadata:
+  name: openebs-zfspv-bin
+  namespace: kube-system # should be the same namespace where it is getting mounted
+data:
+  zfs: |
+    #!/bin/sh
+    if [ -x /host/sbin/zfs ]; then
+      chroot /host /sbin/zfs "$@"
+    elif [ -x /host/usr/sbin/zfs ]; then
+      chroot /host /usr/sbin/zfs "$@"
+    else
+      chroot /host zfs "$@"
+    fi
+
+---
+
 kind: DaemonSet
 apiVersion: apps/v1
 metadata:
@@ -1607,18 +1625,13 @@ spec:
               mountPath: /dev
             - name: encr-keys
               mountPath: /home/keys
-            - name: zfs-bin
+            - name: chroot-zfs
               mountPath: /sbin/zfs
-            - name: libzpool
-              mountPath: /lib/libzpool.so.2
-            - name: libzfscore
-              mountPath: /lib/libzfs_core.so.1
-            - name: libzfs
-              mountPath: /lib/libzfs.so.2
-            - name: libuutil
-              mountPath: /lib/libuutil.so.1
-            - name: libnvpair
-              mountPath: /lib/libnvpair.so.1
+              subPath: zfs
+            - name: host-root
+              mountPath: /host
+              mountPropagation: "HostToContainer"
+              readOnly: true
             - name: pods-mount-dir
               mountPath: /var/lib/kubelet/
               # needed so that any mounts setup inside this container are
@@ -1633,30 +1646,14 @@ spec:
           hostPath:
             path: /home/keys
             type: DirectoryOrCreate
-        - name: zfs-bin
+        - name: chroot-zfs
+          configMap:
+            defaultMode: 0555
+            name: openebs-zfspv-bin
+        - name: host-root
           hostPath:
-            path: /sbin/zfs
-            type: File
-        - name: libzpool
-          hostPath:
-            path: /lib/libzpool.so.2.0.0
-            type: File
-        - name: libzfscore
-          hostPath:
-            path: /lib/libzfs_core.so.1.0.0
-            type: File
-        - name: libzfs
-          hostPath:
-            path: /lib/libzfs.so.2.0.0
-            type: File
-        - name: libuutil
-          hostPath:
-            path: /lib/libuutil.so.1.0.1
-            type: File
-        - name: libnvpair
-          hostPath:
-            path: /lib/libnvpair.so.1.0.1
-            type: File
+            path: /
+            type: Directory
         - name: registration-dir
           hostPath:
             path: /var/lib/kubelet/plugins_registry/