diff --git a/mibios/glamr/tables.py b/mibios/glamr/tables.py
index a03f991..5f3914a 100644
--- a/mibios/glamr/tables.py
+++ b/mibios/glamr/tables.py
@@ -294,6 +294,7 @@ def order_storage_size(self, qs, is_descending):
 
 
 class FileTable(OmicsFileTable):
+    """ List files belonging to a sample """
     class Meta:
         model = omics_models.File
         fields = ['download_url', 'filetype', 'size', 'modtime']
diff --git a/mibios/omics/models.py b/mibios/omics/models.py
index cda6504..27f1132 100644
--- a/mibios/omics/models.py
+++ b/mibios/omics/models.py
@@ -1033,7 +1033,12 @@ def public_root(self):
     @property
     def relpath(self):
         """ The path relative to the common path prefix """
-        return self.path.relative_to(self.root)
+        if self.root:
+            return self.path.relative_to(self.root)
+        elif self.path.is_absolute():
+            raise ValueError('path is absolute abnd no root configured')
+        else:
+            return self.path
 
     @property
     def relpublic(self):
@@ -1042,12 +1047,15 @@ def relpublic(self):
 
         This property may be exposed on a public page.
 
-        Returns None if no public path is set or if the common prefix is not
-        configured.
+        Returns None if no public path is set.
         """
-        if self.public_root is None or self.public is None:
-            return None
-        return self.public.relative_to(self.public_root)
+        if self.public_root:
+            return self.public.relative_to(self.public_root)
+        elif self.public and self.public.is_absolute():
+            raise ValueError('public path is absolute and no root configured')
+        else:
+            # is a rel path or None
+            return self.public
 
     def compute_public_path(self):
         """
diff --git a/mibios/omics/settings.py b/mibios/omics/settings.py
index c71d04d..cc374ac 100644
--- a/mibios/omics/settings.py
+++ b/mibios/omics/settings.py
@@ -62,9 +62,8 @@ def get_db_settings(db_dir='.', db_infix=''):
 """ root Globus url for file app, publicly shared directory """
 
 PUBLIC_DATA_ROOT = None
-""" path to publicly accessible directory on staging server, this needs to be
-set even on other deployments so that relative paths to the public files can be
-computed """
+""" path to root of publicly accessible directory tree on staging server, leave
+at None on other deployments """
 
 OMICS_CHECKOUT_FILE = None
 """ path to the file checkout listing """
diff --git a/mibios/omics/tables.py b/mibios/omics/tables.py
index 3ee5ba2..c8bcc6c 100644
--- a/mibios/omics/tables.py
+++ b/mibios/omics/tables.py
@@ -30,14 +30,14 @@ class Meta:
 
     def render_download_url(self, value, record):
         if record.public:
-            path = record.public.relative_to(File.get_public_prefix())
-            if value:
-                return format_html('<a href="{}">{}</a>', value, path)
-            else:
-                return f'{path} (unavailable)'
+            path = record.relpublic
         else:
-            path = record.path.relative_to(File.get_path_prefix())
-            return str(path)
+            path = record.relpath
+
+        if value:
+            return format_html('<a href="{}">{}</a>', value, path)
+        else:
+            return f'{"" if record.public else "*"}{path}'
 
     def order_download_url(self, queryset, is_descending):
         qs = queryset.annotate(path0=Coalesce('public', 'path'))