Add ability to run the provisioner directly on the ZFS host.

The default is to run kubernetes-zfs-provisioner in a container and
create datasets via SSH on a remote host.
To do that, the docker image is created with the zfs and
update-permissions stubs that will both call commands on the remote host
using SSH.

Allows running kubernetes-zfs-provisioner directly on the ZFS host by
making the update-permissions script presence optional. The zfs stub is
already optional because it merely replaces the command of the same name
on the remote host. The provisionner now uses the command specified in
the ZFS_UPDATE_PERMISSIONS environment variable, which is set to
/usr/bin/update-permissions by default in the docker image, otherwise it
falls back to chmod.

Fixes #130.

docker/Dockerfile

@@ -11,3 +11,4 @@ COPY docker/update-permissions.sh /usr/bin/update-permissions
 COPY kubernetes-zfs-provisioner /usr/bin/
 
 USER zfs:root
+ENV ZFS_UPDATE_PERMISSIONS=/usr/bin/update-permissions

docker/update-permissions.sh

@@ -2,10 +2,9 @@
 
 set -eo pipefail
 
-zfs_mod="${ZFS_MOD:-g+w}"
-chmod_bin=${ZFS_CHOWN_BIN:-sudo -H chmod}
+chmod_bin=${ZFS_CHMOD_BIN:-sudo -H chmod}
 
-zfs_host="${1}"
-zfs_mountpoint="${2}"
+# Do not try to manually modify these Env vars, they will be updated by the provisioner just before invoking the script.
+zfs_host="${ZFS_HOST}"
 
-ssh "${zfs_host}" "${chmod_bin} ${zfs_mod} ${zfs_mountpoint}"
+ssh "${zfs_host}" "${chmod_bin} ${*}"

pkg/zfs/zfs.go

@@ -114,7 +114,20 @@ func (z *zfsImpl) SetPermissions(dataset *Dataset) error {
 	if dataset.Mountpoint == "" {
 		return fmt.Errorf("undefined mountpoint for dataset: %s", dataset.Name)
 	}
-	cmd := exec.Command("update-permissions", dataset.Hostname, dataset.Mountpoint)
+	updatePermissions, found := os.LookupEnv("ZFS_UPDATE_PERMISSIONS")
+	if !found {
+		updatePermissions = "chmod"
+	}
+	mode, found := os.LookupEnv("ZFS_MOD")
+	if !found {
+		mode = "g+w"
+	}
+	globalLock.Lock()
+	defer globalLock.Unlock()
+	if err := setEnvironmentVars(dataset.Hostname); err != nil {
+		return nil, err
+	}
+	cmd := exec.Command(updatePermissions, mode, dataset.Mountpoint)
 	out, err := cmd.CombinedOutput()
 	if err != nil {
 		return fmt.Errorf("could not update permissions on '%s': %w: %s", dataset.Hostname, err, out)