diff --git a/doc/examples/defaults.conf-rsh b/doc/examples/defaults.conf-rsh
index 140201eb..84540798 100644
--- a/doc/examples/defaults.conf-rsh
+++ b/doc/examples/defaults.conf-rsh
@@ -4,7 +4,8 @@
 # Example defaults.conf file for clusters using rsh instead of ssh.
 #
 # To enable this file, install it in one of the following locations:
-#       /etc/clustershell/defaults.conf (system-wide)
+#       $CLUSTERSHELL_CFGDIR/defaults.conf (global configuration, default to
+#       /etc/clustershell/defaults.conf)
 #       $XDG_CONFIG_HOME/clustershell/defaults.conf (per-user)
 #       $HOME/.local/etc/clustershell/defaults.conf (per-user)
 #
diff --git a/doc/sphinx/config.rst b/doc/sphinx/config.rst
index 1320d48f..204baee2 100644
--- a/doc/sphinx/config.rst
+++ b/doc/sphinx/config.rst
@@ -8,13 +8,16 @@ Configuration
 clush
 -----
 
-The following configuration file defines system-wide default values for
+The following configuration file defines global default values for
 several *clush* tool parameters::
 
-    /etc/clustershell/clush.conf
+    $CLUSTERSHELL_CFGDIR/clush.conf
+    
+If *$CLUSTERSHELL_CFGDIR* is not defined, */etc/clustershell/clush.conf* will
+be used,
 
-*clush* settings might then be overridden per user if one of the following
-files is found, in priority order::
+*clush* settings might then be overridden (globally, or per user) if one of the
+following files is found, in priority order::
 
     $XDG_CONFIG_HOME/clustershell/clush.conf
     $HOME/.config/clustershell/clush.conf (only if $XDG_CONFIG_HOME is not defined)
@@ -123,13 +126,16 @@ ClusterShell loads *groups.conf* configuration files that define how to
 obtain node groups configuration, ie. the way the library should access
 file-based or external node group **sources**.
 
-The following configuration file defines system-wide default values for
+The following configuration file defines global default values for
 *groups.conf*::
 
-    /etc/clustershell/groups.conf
+    $CLUSTERSHELL_CFGDIR/groups.conf
+    
+If *$CLUSTERSHELL_CFGDIR* is not defined, */etc/clustershell/groups.conf* will
+be used,
 
-*groups.conf* settings might then be overridden per user if one of the
-following files is found, in priority order::
+*groups.conf* settings might then be overridden (globally, or per user) if one
+of the following files is found, in priority order::
 
     $XDG_CONFIG_HOME/clustershell/groups.conf
     $HOME/.config/clustershell/groups.conf (only if $XDG_CONFIG_HOME is not defined)
@@ -542,10 +548,13 @@ in *defaults.conf*.
 
 The following configuration file defines ClusterShell system-wide defaults::
 
-    /etc/clustershell/defaults.conf
+    $CLUSTERSHELL_CFGDIR/defaults.conf
 
-*defaults.conf* settings might then be overridden per user if one of the
-following files is found, in priority order::
+If *$CLUSTERSHELL_CFGDIR* is not defined, */etc/clustershell/defaults.conf*
+will be used,
+
+*defaults.conf* settings might then be overridden (globally, or per user) if
+one of the following files is found, in priority order::
 
     $XDG_CONFIG_HOME/clustershell/defaults.conf
     $HOME/.config/clustershell/defaults.conf (only if $XDG_CONFIG_HOME is not defined)
diff --git a/doc/sphinx/release.rst b/doc/sphinx/release.rst
index fbd1f116..574aa201 100644
--- a/doc/sphinx/release.rst
+++ b/doc/sphinx/release.rst
@@ -564,8 +564,11 @@ versions.
 Configuration files
 """""""""""""""""""
 
-When ``$XDG_CONFIG_HOME`` is defined, ClusterShell will use it to search for
-additional configuration files.
+When ``$CLUSTERSHELL_CFGDIR`` or ``$XDG_CONFIG_HOME`` are defined,
+ClusterShell will use them to search for additional configuration files.
+
+If ``$CLUSTERSHELL_CFGDIR`` is not defined, the global configuration files will
+be searched for in `/etc/clustershell`
 
 PIP user installation support
 """""""""""""""""""""""""""""
diff --git a/doc/txt/clush.conf.txt b/doc/txt/clush.conf.txt
index 34b928fe..938dbdf8 100644
--- a/doc/txt/clush.conf.txt
+++ b/doc/txt/clush.conf.txt
@@ -23,7 +23,8 @@ following order:
  1. command-line options
  2. user configuration file (*$XDG_CONFIG_HOME/clustershell/clush.conf*)
  3. local pip user installation (*$HOME/.local/etc/clustershell/clush.conf*)
- 4. system-wide configuration file (*/etc/clustershell/clush.conf*)
+ 4. global configuration file (*$CLUSTERSHELL_CFGDIR/clush.conf*, defaults to
+    */etc/clustershell/clush.conf*)
 
 For each parameter, the first obtained value will be used.
 
@@ -122,8 +123,9 @@ Simple configuration file.
 FILES
 =====
 
-*/etc/clustershell/clush.conf*
-  System-wide clush configuration file.
+*$CLUSTERSHELL_CFGDIR/clush.conf*
+  Global clush configuration file. If $CLUSTERSHELL_CFGDIR is not defined,
+  */etc/slutershell/clush.conf* is used instead.
 
 *$XDG_CONFIG_HOME/clustershell/clush.conf*
   User configuration file for clush. If $XDG_CONFIG_HOME is not defined,
diff --git a/doc/txt/clush.txt b/doc/txt/clush.txt
index 61aa8465..09c1df0a 100644
--- a/doc/txt/clush.txt
+++ b/doc/txt/clush.txt
@@ -278,8 +278,9 @@ Copy files
 FILES
 =====
 
-*/etc/clustershell/clush.conf*
-  System-wide clush configuration file.
+*$CLUSTERSHELL_CFGDIR/clush.conf*
+  Global clush configuration file. If $CLUSTERSHELL_CFGDIR is not defined,
+  */etc/clustershell/clush.conf* is used instead.
 
 *$XDG_CONFIG_HOME/clustershell/clush.conf*
   User configuration file for clush. If $XDG_CONFIG_HOME is not defined,
diff --git a/doc/txt/groups.conf.txt b/doc/txt/groups.conf.txt
index e361653c..9676526b 100644
--- a/doc/txt/groups.conf.txt
+++ b/doc/txt/groups.conf.txt
@@ -22,7 +22,8 @@ following sources in the following order:
 
  1. user configuration file (*$XDG_CONFIG_HOME/clustershell/groups.conf*)
  2. local pip user installation (*$HOME/.local/etc/clustershell/groups.conf*)
- 3. system-wide configuration file (*/etc/clustershell/groups.conf*)
+ 3. Global configuration file (*$CLUSTERSHELL_CFGDIR/groups.conf*, defaults to
+    */etc/clustershell/groups.conf*)
 
 If no *groups.conf* is found, group support will be disabled.
 
@@ -159,13 +160,14 @@ Simple configuration file for local groups and slurm partitions binding.
 FILES
 =====
 
-*/etc/clustershell/groups.conf*
-  System-wide node groups configuration file.
+*$CLUSTERSHELL_CFGDIR/groups.conf* (defaults to */etc/clustershell/groups.conf*)
+  Global node groups configuration file.
 
-*/etc/clustershell/groups.conf.d/*
+*$CLUSTERSHELL_CFGDIR/groups.conf.d/* (defaults to
+  */etc/clustershell/groups.conf.d/*)
   Recommended directory for additional configuration files.
 
-*/etc/clustershell/groups.d/*
+*$CLUSTERSHELL_CFGDIR/groups.d/* (defaults to */etc/clustershell/groups.d/*)
   Recommended directory for *autodir*, where native group definition files
   (.yaml files) are found.
 
diff --git a/lib/ClusterShell/Defaults.py b/lib/ClusterShell/Defaults.py
index ce8b4741..a4406688 100644
--- a/lib/ClusterShell/Defaults.py
+++ b/lib/ClusterShell/Defaults.py
@@ -90,7 +90,9 @@ def _distant_workerclass(defaults):
 
 def config_paths(config_name):
     """Return default path list for a ClusterShell config file name."""
-    return ['/etc/clustershell/%s' % config_name, # system-wide config file
+    return [os.path.join(os.environ.get('CLUSTERSHELL_CFGDIR',
+                                        '/etc/clustershell/%s'),
+			             config_name), # global config file
             # default pip --user config file
             os.path.expanduser('~/.local/etc/clustershell/%s' % config_name),
             # per-user config (top override)
diff --git a/tests/CLIConfigTest.py b/tests/CLIConfigTest.py
index 2853398c..42e6bf1c 100644
--- a/tests/CLIConfigTest.py
+++ b/tests/CLIConfigTest.py
@@ -319,6 +319,59 @@ def testClushConfigWithInstalledConfig(self):
         options, _ = parser.parse_args([])
         config = ClushConfig(options)
 
+    def testClushConfigCustomGlobal(self):
+        """test CLI.Config.ClushConfig (CLUSTERSHELL_CFGDIR global custom
+        config)
+        """
+
+        # Save existing environment variable, if it's defined
+        custom_config_save = os.environ.get('CLUSTERSHELL_CFGDIR')
+
+        # Create fake CLUSTERSHELL_CFGDIR
+        custom_cfg_dir = make_temp_dir()
+
+        try:
+            os.environ['CLUSTERSHELL_CFGDIR'] = custom_cfg_dir
+
+            cfgfile = open(os.path.join(custom_cfg_dir, 'clush.conf'), 'w')
+            cfgfile.write(dedent("""
+                [Main]
+                fanout: 42
+                connect_timeout: 14
+                command_timeout: 0
+                history_size: 100
+                color: never
+                verbosity: 2
+                ssh_user: joebar
+                ssh_path: ~/bin/ssh
+                ssh_options: -oSomeDummyUserOption=yes
+                """))
+
+            cfgfile.flush()
+            parser = OptionParser("dummy")
+            parser.install_clush_config_options()
+            parser.install_display_options(verbose_options=True)
+            parser.install_connector_options()
+            options, _ = parser.parse_args([])
+            config = ClushConfig(options) # filename=None to use defaults!
+            self.assertEqual(config.color, THREE_CHOICES[1])
+            self.assertEqual(config.verbosity, VERB_VERB) # takes biggest
+            self.assertEqual(config.fanout, 42)
+            self.assertEqual(config.connect_timeout, 14)
+            self.assertEqual(config.command_timeout, 0)
+            self.assertEqual(config.ssh_user, 'joebar')
+            self.assertEqual(config.ssh_path, '~/bin/ssh')
+            self.assertEqual(config.ssh_options, '-oSomeDummyUserOption=yes')
+            cfgfile.close()
+
+        finally:
+            if custom_config_save:
+                os.environ['CLUSTERSHELL_CFGDIR'] = custom_config_save
+            else:
+                del os.environ['CLUSTERSHELL_CFGDIR']
+            shutil.rmtree(custom_cfg_dir, ignore_errors=True)
+
+
     def testClushConfigUserOverride(self):
         """test CLI.Config.ClushConfig (XDG_CONFIG_HOME user config)"""