Add an option to setup mountpoints when fetching a plugin

Add the option --mountpoints/-M to the fetch subcommand. It gives the
possibility to setup one or many mountpoints at the jail creation of
a plugin, before the initial start. It mimicks the format of the Docker
--volume option: source:destination[:options]

Example:
  iocage fetch -P ./plugin.json -M /mnt/tank/plugin-data:/data:ro

iocage_cli/fetch.py

@@ -150,6 +150,12 @@ def validate_count(ctx, param, value):
     '--proxy', '-S', default=None,
     help='Provide proxy to use for creating jail'
 )
+@click.option(
+    "--mountpoints", "-M", multiple=True,
+    help="Specify a mountpoint to setup in the jail. Format is "
+         "source:destination[:options].\n(only applicable if "
+         "fetching a plugin)"
+)
 def cli(**kwargs):
     """CLI command that calls fetch_release()"""
     release = kwargs.get("release", None)

iocage_lib/ioc_plugin.py

@@ -46,6 +46,7 @@
 import iocage_lib.ioc_create
 import iocage_lib.ioc_destroy
 import iocage_lib.ioc_exec
+import iocage_lib.ioc_fstab
 import iocage_lib.ioc_list
 import iocage_lib.ioc_json
 import iocage_lib.ioc_start
@@ -94,6 +95,7 @@ def __init__(
             self.plugin_json_path = None
         self.plugin = plugin
         self.jail = jail
+        self.mountpoints = kwargs.pop("mountpoints", [])
         self.http = kwargs.pop("http", True)
         self.hardened = kwargs.pop("hardened", False)
         self.date = datetime.datetime.utcnow().strftime("%F")
@@ -321,6 +323,7 @@ def fetch_plugin(self, props, num, accept_license):
 
         try:
             jaildir, _conf, repo_dir = self.__fetch_plugin_create__(props)
+            self.__fetch_plugin_add_mountpoints__(jaildir)
             # As soon as we create the jail, we should write the plugin manifest to jail directory
             # This is done to ensure that subsequent starts of the jail make use of the plugin
             # manifest as required
@@ -607,6 +610,52 @@ def __fetch_plugin_create__(self, create_props):
 
         return jaildir, _conf, repo_dir
 
+    def __fetch_plugin_add_mountpoints__(self, jaildir):
+        for mountpoint in self.mountpoints:
+            fstype = "nullfs"
+            options = "rw"
+            dump = "0"
+            _pass = "0"
+
+            parts = mountpoint.split(":")
+            if len(parts) < 2 or len(parts) > 3:
+                raise RuntimeError(
+                    f"Ignoring invalid mountpoint `{mountpoint}`, expecting "
+                    "`source:destination[:options]`."
+                )
+            else:
+                source = parts[0].strip()
+                destination = parts[1].strip()
+                if len(parts) == 3:
+                    options = parts[2]
+
+            if (not source or source[0] != "/"
+                or not destination or destination[0] != "/"
+                or not options):
+                raise RuntimeError(
+                    f"Ignoring invalid mountpoint `{mountpoint}`, source and "
+                    "destination must be absolute path, options cannot be "
+                    "empty."
+                )
+
+            destination = f"{jaildir}/root{destination}"
+            if destination and len(destination) > 88:
+                iocage_lib.ioc_common.logit(
+                    {
+                        "level":
+                        "WARNING",
+                        "message":
+                        "The destination's mountpoint exceeds 88 "
+                        "characters, this may cause failure!"
+                    },
+                    silent=self.silent)
+
+            os.makedirs(destination, exist_ok=True)
+            iocage_lib.ioc_fstab.IOCFstab(
+                self.jail, "add", source, destination,
+                fstype, options, dump, _pass
+            )
+
     def __fetch_plugin_install_packages__(self, jaildir, conf, pkg_repos,
                                           create_props, repo_dir):
         """Attempts to start the jail and install the packages"""