diff --git a/src/luamb/_entrypoint.py b/src/luamb/_entrypoint.py
index e97096b..a774971 100644
--- a/src/luamb/_entrypoint.py
+++ b/src/luamb/_entrypoint.py
@@ -1,4 +1,3 @@
-import os
 import sys
 
 
@@ -16,21 +15,19 @@ def error(msg, exit_status=1):
         print(msg, file=sys.stderr)
         sys.exit(exit_status)
 
+    import os
+
     from ._datadirs import ENVS_DIR
     from ._exceptions import LuambException
     from ._hererocks import import_hererocks
     from ._luamb import Luamb
 
-    hererocks = import_hererocks()
-    if not hererocks:
-        error("'hererocks' is not installed")
-
     luamb = Luamb(
         envs_dir=ENVS_DIR,
         active_env=os.environ.get('LUAMB_ACTIVE_ENV'),
         lua_default=os.environ.get('LUAMB_LUA_DEFAULT'),
         luarocks_default=os.environ.get('LUAMB_LUAROCKS_DEFAULT'),
-        hererocks=hererocks,
+        hererocks=import_hererocks(),
     )
 
     try:
diff --git a/src/luamb/_luamb.py b/src/luamb/_luamb.py
index 66b3f44..3910d40 100644
--- a/src/luamb/_luamb.py
+++ b/src/luamb/_luamb.py
@@ -6,16 +6,17 @@
 import shutil
 import sys
 from collections import OrderedDict
-from importlib import import_module
 from io import StringIO
 from typing import TYPE_CHECKING
 
 from . import __version__
 from ._exceptions import LuambException
+from ._hererocks import update_hererocks
 
 
 if TYPE_CHECKING:
     from pathlib import Path
+    from types import ModuleType
 
 
 class CMD(object):
@@ -47,10 +48,10 @@ def render_help(self):
                 continue
             cmd_str = cmd
             if cmd_info['aliases']:
-                cmd_str = '{0: <6}(aliases: {1})'.format(
+                cmd_str = '{0: <8}(aliases: {1})'.format(
                     cmd_str, ', '.join(cmd_info['aliases']))
             if cmd_info['desc']:
-                cmd_str = '{0: <38}{1}'.format(cmd_str, cmd_info['desc'])
+                cmd_str = '{0: <40}{1}'.format(cmd_str, cmd_info['desc'])
             help_list.append(cmd_str)
         return '\n'.join(help_list)
 
@@ -135,21 +136,21 @@ class Luamb(object):
 
     cmd = CMD()
 
+    # {product_key: {version_alias: version}}
+    supported_versions: dict[str, dict[str, str]]
+
     def __init__(
-        self, envs_dir: Path, active_env: str | None = None,
-        lua_default: str | None = None,
-        luarocks_default: str | None = None,
-        hererocks=None,
+        self, *,
+        envs_dir: Path, active_env: str | None = None,
+        lua_default: str | None = None, luarocks_default: str | None = None,
+        hererocks: ModuleType | None,
     ):
         self.envs_dir = envs_dir
         self.active_env = active_env
         self.lua_default = lua_default
         self.luarocks_default = luarocks_default
-        self.hererocks = hererocks or import_module('hererocks')
-        self.supported_versions = {
-            product_key: self._fetch_supported_versions(cls_name)
-            for product_key, cls_name in self.product_hererocks_classes.items()
-        }
+        self.hererocks = hererocks
+        self.supported_versions = {}
 
     def run(self, argv=None):
         if not argv:
@@ -198,6 +199,8 @@ def cmd_off(self, argv):
     @cmd.add('mk', 'new', 'create')
     def cmd_mk(self, argv):
         """create new environment"""
+        if not self._check_hererocks_is_installed():
+            return
         parser = argparse.ArgumentParser(
             prog='luamb mk',
             add_help=False,
@@ -375,6 +378,8 @@ def cmd_rm(self, argv):
     @cmd.add('info', 'show')
     def cmd_info(self, argv):
         """show environment info"""
+        if not self._check_hererocks_is_installed():
+            return
         if '-h' in argv or '--help' in argv:
             print("usage: luamb info [ENV_NAME]")
             return
@@ -387,6 +392,8 @@ def cmd_info(self, argv):
     @cmd.add('ls', 'list')
     def cmd_ls(self, argv):
         """list available environments"""
+        if not self._check_hererocks_is_installed():
+            return
         parser = argparse.ArgumentParser(prog='luamb ls')
         parser.add_argument(
             '-s', '--short',
@@ -404,6 +411,19 @@ def cmd_ls(self, argv):
             if detail:
                 print('\n')
 
+    @cmd.add('update', 'upgrade')
+    def cmd_update(self, argv):
+        """update hererocks"""
+        if '-h' in argv or '--help' in argv:
+            print("usage: luamb update")
+            return
+        print('updating hererocks')
+        updated = update_hererocks()
+        if updated:
+            print('updated')
+        else:
+            print('hererocks is already up-to-date')
+
     @contextlib.contextmanager
     def _maybe_capture_output(self, capture_output):
         string_buffer = StringIO()
@@ -470,7 +490,12 @@ def _fetch_supported_versions(self, hererocks_cls_name):
         return versions
 
     def _get_supported_versions(self, product_key, raise_exc=True):
-        versions = self.supported_versions[product_key]
+        supported_versions = self.supported_versions
+        if not supported_versions:
+            for prod_key, cls_name in self.product_hererocks_classes.items():
+                supported_versions[prod_key] = self._fetch_supported_versions(
+                    cls_name)
+        versions = supported_versions[product_key]
         if versions or not raise_exc:
             return versions
         raise LuambException(
@@ -524,3 +549,9 @@ def _is_local_path_or_git_uri(self, version_string, skip_path_check=False):
                 "'{}' is not a directory ".format(version_string)
             )
         return True
+
+    def _check_hererocks_is_installed(self) -> bool:
+        if self.hererocks is None:
+            print("'hererocks' is not installed, run 'luamb update'")
+            return False
+        return True