diff --git a/lib/spack/spack/architecture.py b/lib/spack/spack/architecture.py
index 57e266722e6da1494f3636651b392617c6507e36..b14de35109e0939df612c554e349103843e73b85 100644
--- a/lib/spack/spack/architecture.py
+++ b/lib/spack/spack/architecture.py
@@ -83,7 +83,6 @@
import llnl.util.tty as tty
import spack
-import spack.compilers
from spack.util.naming import mod_to_class
from spack.util.environment import get_path
from spack.util.multiproc import parmap
@@ -276,6 +275,8 @@ def find_compilers(self, *paths):
# Once the paths are cleaned up, do a search for each type of
# compiler. We can spawn a bunch of parallel searches to reduce
# the overhead of spelunking all these directories.
+ # NOTE: we import spack.compilers here to avoid init order cycles
+ import spack.compilers
types = spack.compilers.all_compiler_types()
compiler_lists = parmap(lambda cmp_cls:
self.find_compiler(cmp_cls, *filtered_path),
diff --git a/lib/spack/spack/cmd/config.py b/lib/spack/spack/cmd/config.py
index c189e37036b50cea6116f0daad6f8f99aa7c05d2..5e041192e299b68e19425837a94fa61f44a6f9b4 100644
--- a/lib/spack/spack/cmd/config.py
+++ b/lib/spack/spack/cmd/config.py
@@ -29,13 +29,8 @@
def setup_parser(subparser):
# User can only choose one
- scope_group = subparser.add_mutually_exclusive_group()
- scope_group.add_argument(
- '--user', action='store_const', const='user', dest='scope',
- help="Use config file in user home directory (default).")
- scope_group.add_argument(
- '--site', action='store_const', const='site', dest='scope',
- help="Use config file in spack prefix.")
+ subparser.add_argument('--scope', choices=spack.config.config_scopes,
+ help="Configuration scope to read/modify.")
sp = subparser.add_subparsers(metavar='SUBCOMMAND', dest='config_command')
diff --git a/lib/spack/spack/config.py b/lib/spack/spack/config.py
index dec43726a03f208cd6ea78a6e555b1cfcaceae78..6a67f01d66fdcf5c6766d008cef30f2a99cc2231 100644
--- a/lib/spack/spack/config.py
+++ b/lib/spack/spack/config.py
@@ -30,18 +30,47 @@
When Spack runs, it pulls configuration data from several config
directories, each of which contains configuration files. In Spack,
-there are two configuration scopes:
-
-1. ``site``: Spack loads site-wide configuration options from
- ``$(prefix)/etc/spack/``.
-
-2. ``user``: Spack next loads per-user configuration options from
- ``~/.spack/``.
-
-Spack may read configuration files from both of these locations. When
-configurations conflict, the user config options take precedence over
-the site configurations. Each configuration directory may contain
-several configuration files, such as compilers.yaml or mirrors.yaml.
+there are three configuration scopes (lowest to highest):
+
+1. ``defaults``: Spack loads default configuration settings from
+ ``$(prefix)/etc/spack/defaults/``. These settings are the "out of the
+ box" settings Spack will use without site- or user- modification, and
+ this is where settings that are versioned with Spack should go.
+
+2. ``site``: This scope affects only this *instance* of Spack, and
+ overrides the ``defaults`` scope. Configuration files in
+ ``$(prefix)/etc/spack/`` determine site scope. These can be used for
+ per-project settings (for users with their own spack instance) or for
+ site-wide settings (for admins maintaining a common spack instance).
+
+3. ``user``: User configuration goes in the user's home directory,
+ specifically in ``~/.spack/``.
+
+Spack may read configuration files from any of these locations. When
+configurations conflict, settings from higher-precedence scopes override
+lower-precedence settings.
+
+fCommands that modify scopes (``spack compilers``, ``spack config``,
+etc.) take a ``--scope=<name>`` parameter that you can use to control
+which scope is modified.
+
+For each scope above, there can *also* be platform-specific
+overrides. For example, on Blue Gene/Q machines, Spack needs to know the
+location of cross-compilers for the compute nodes. This configuration is
+in ``etc/spack/defaults/bgq/compilers.yaml``. It will take precedence
+over settings in the ``defaults`` scope, but can still be overridden by
+settings in ``site``, ``site/bgq``, ``user``, or ``user/bgq``. So, the
+full list of scopes and their precedence is:
+
+1. ``defaults``
+2. ``defaults/<platform>``
+3. ``site``
+4. ``site/<platform>``
+5. ``user``
+6. ``user/<platform>``
+
+Each configuration directory may contain several configuration files,
+such as compilers.yaml or mirrors.yaml.
=========================
Configuration file format
@@ -118,6 +147,7 @@
Will make Spack take compilers *only* from the user configuration, and
the site configuration will be ignored.
+
"""
import copy
@@ -135,6 +165,7 @@
from llnl.util.filesystem import mkdirp
import spack
+import spack.architecture
from spack.error import SpackError
import spack.schema
@@ -267,16 +298,30 @@ def clear(self):
"""Empty cached config information."""
self.sections = {}
+#
+# Below are configuration scopes.
+#
+# Each scope can have per-platfom overrides in subdirectories of the
+# configuration directory.
+#
+_platform = spack.architecture.platform().name
+
"""Default configuration scope is the lowest-level scope. These are
versioned with Spack and can be overridden by sites or users."""
-ConfigScope('defaults', os.path.join(spack.etc_path, 'spack', 'defaults'))
+_defaults_path = os.path.join(spack.etc_path, 'spack', 'defaults')
+ConfigScope('defaults', _defaults_path)
+ConfigScope('defaults/%s' % _platform, os.path.join(_defaults_path, _platform))
"""Site configuration is per spack instance, for sites or projects.
No site-level configs should be checked into spack by default."""
-ConfigScope('site', os.path.join(spack.etc_path, 'spack'))
+_site_path = os.path.join(spack.etc_path, 'spack')
+ConfigScope('site', _site_path)
+ConfigScope('site/%s' % _platform, os.path.join(_site_path, _platform))
"""User configuration can override both spack defaults and site config."""
-ConfigScope('user', spack.user_config_path)
+_user_path = spack.user_config_path
+ConfigScope('user', _user_path)
+ConfigScope('user/%s' % _platform, os.path.join(_user_path, _platform))
def highest_precedence_scope():