.. _configuration:
==============================
Configuration Files in Spack
==============================
Spack has many configuration files. Here is a quick list of them, in
case you want to skip directly to specific docs:
* :ref:`compilers.yaml <compiler-config>`
* :ref:`config.yaml <config-yaml>`
* :ref:`mirrors.yaml <mirrors>`
* :ref:`modules.yaml <modules>`
* :ref:`packages.yaml <build-settings>`
* :ref:`repos.yaml <repositories>`
-------------------------
YAML Format
-------------------------
Spack configuration files are written in YAML. We chose YAML because
it's human readable, but also versatile in that it supports dictionaries,
lists, and nested sections. For more details on the format, see `yaml.org
<http://yaml.org>`_ and `libyaml <http://pyyaml.org/wiki/LibYAML>`_.
Here is an example ``config.yaml`` file:
.. code-block:: yaml
config:
install_tree: $spack/opt/spack
module_roots:
lmod: $spack/share/spack/lmod
build_stage:
- $tempdir
- /nfs/tmp2/$user
Each spack configuration files is nested under a top-level section
corresponding to its name. So, ``config.yaml`` starts with ``config:``,
and ``mirrors.yaml`` starts with ``mirrors:``, etc.
.. _configuration-scopes:
-------------------------
Configuration Scopes
-------------------------
Spack pulls configuration data from files in several directories. There
are four configuration scopes. From lowest to highest:
#. **defaults**: Stored in ``$(prefix)/etc/spack/defaults/``. These are
the "factory" settings. Users should generally not modify the settings
here, but should override them in other configuration scopes. The
defaults here will change from version to version of Spack.
#. **system**: Stored in ``/etc/spack``. These are settings for this
machine, or for all machines on which this file system is
mounted. The site scope can be used for settings idiosyncratic to a
particular machine, such as the locations of compilers or external
packages. These settings are presumably controlled by someone with
root access on the machine.
#. **site**: Stored in ``$(prefix)/etc/spack/``. Settings here affect
only *this instance* of Spack, and they override defaults. The site
scope can can be used for per-project settings (one spack instance per
project) or for site-wide settings on a multi-user machine (e.g., for
a common spack instance).
3. **user**: Stored in the home directory: ``~/.spack/``. These settings
affect all instances of Spack and take higher precedence than site or
default scopes.
3. **command line**: Optionally specified by the user on the command
line. These settings take the highest precedence. If multiple
scopes are listed on the command line, they are ordered from lowest
to highest precedence.
Each configuration directory may contain several configuration files,
such as ``config.yaml``, ``compilers.yaml``, or ``mirrors.yaml``. When
configurations conflict, settings from higher-precedence scopes override
lower-precedence settings.
Commands that modify scopes (e.g., ``spack compilers``, ``spack repo``,
etc.) take a ``--scope=<name>`` parameter that you can use to control
which scope is modified. By default they modify the highest-precedence
scope.
.. _command-line-scopes:
^^^^^^^^^^^^^^^^^^^
Command-line Scopes
^^^^^^^^^^^^^^^^^^^
In addition to the ``system``, ``site``, and ``user`` scopes, you may add
configuration scopes directly on the command line with the
``--config-scope`` argument, or ``-C`` for short.
For example, the following adds two configuration scopes, named `scopea`
and `scopeb`, to a `spack spec` command:
.. code-block:: console
$ spack -C ~/myscopes/scopea -C ~/myscopes/scopeb spec ncurses
Command-line scopes come *after* the ``spack`` command and *before* the
subcommand, and they specify a single path to a directory full of
configuration files. You can add the same configuration files to that
directory that you can add to any other sope (``config.yaml``,
``packages.yaml``, etc.).
If multiple scopes are provided:
1. each must be preceded with the ``--config-scope`` or ``-C`` flag.
2. they must be ordered from lowest to highest precedence.
"""""""""""""""""""""""""""""""""""""""""""
Example: scopes for release and development
"""""""""""""""""""""""""""""""""""""""""""
suppose that you need to support simultaneous building of release and
development versions of a `mypackage`, where `mypackage` -> `A` -> `B`.
You could create The following files:
.. code-block:: yaml
~/myscopes/release/packages.yaml
--------------------------------
packages:
mypackage:
version: [1.7]
A:
version: [2.3]
B:
version: [0.8]
.. code-block:: yaml
~/myscopes/develop/packages.yaml
--------------------------------
packages:
mypackage:
version: [develop]
A:
version: [develop]
B:
version: [develop]
You can switch between ``release`` and ``develop`` configurations using
configuration arguments. You would type ``spack -C ~/myscopes/release``
when you want to build the designated release versions of ``mypackage``,
``A``, and ``B``, and you would type ``spack -C ~/myscopes/develop`` when
you want to build all of these packages at the ``develop`` version.
"""""""""""""""""""""""""""""""
Example: swapping MPI providers
"""""""""""""""""""""""""""""""
Suppose that you need to build two software packages, `packagea` and
`packageb`. PackageA is Python2-based and PackageB is Python3-based.
PackageA only builds with OpenMPI and PackageB only builds with MPICH.
You can create different configuration scopes for use with Package A and
B:
.. code-block:: yaml
~/myscopes/packgea/packages.yaml
--------------------------------
packages:
python:
version: [2.7.11]
all:
providers:
mpi: [openmpi]
.. code-block:: yaml
~/myscopes/packageb/packages.yaml
--------------------------------
packages:
python:
version: [3.5.2]
all:
providers:
mpi: [mpich]
.. _platform-scopes:
-------------------------
Platform-specific scopes
-------------------------
For each scope above, there can *also* be platform-specific settings.
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 ``system``, ``system/bgq``, ``site``, ``site/bgq``,
``user``, or ``user/bgq``. So, the full scope precedence is:
1. ``defaults``
2. ``defaults/<platform>``
3. ``system``
4. ``system/<platform>``
5. ``site``
6. ``site/<platform>``
7. ``user``
8. ``user/<platform>``
9. ``command-line``
10. ``command-line/<platform>``
You can get the name to use for ``<platform>`` by running ``spack arch
--platform``. The system config scope has a ``<platform>`` section for
sites at which ``/etc`` is mounted on multiple heterogeneous machines.
-------------------------
Scope precedence
-------------------------
When spack queries for configuration parameters, it searches in
higher-precedence scopes first. So, settings in a higher-precedence file
can override those with the same key in a lower-precedence one. For
list-valued settings, Spack *prepends* higher-precedence settings to
lower-precedence settings. Completely ignoring higher-level configuration
options is supported with the ``::`` notation for keys (see
:ref:`config-overrides` below).
^^^^^^^^^^^^^^^^^^^^^^^^
Simple keys
^^^^^^^^^^^^^^^^^^^^^^^^
Let's look at an example of overriding a single key in a Spack file. If
your configurations look like this:
**defaults** scope:
.. code-block:: yaml
config:
install_tree: $spack/opt/spack
module_roots:
lmod: $spack/share/spack/lmod
build_stage:
- $tempdir
- /nfs/tmp2/$user
**site** scope:
.. code-block:: yaml
config:
install_tree: /some/other/directory
Spack will only override ``install_tree`` in the ``config`` section, and
will take the site preferences for other settings. You can see the
final, combined configuration with the ``spack config get <configtype>``
command:
.. code-block:: console
:emphasize-lines: 3
$ spack config get config
config:
install_tree: /some/other/directory
module_roots:
lmod: $spack/share/spack/lmod
build_stage:
- $tempdir
- /nfs/tmp2/$user
$ _
.. _config-overrides:
^^^^^^^^^^^^^^^^^^^^^^^^^^
Overriding entire sections
^^^^^^^^^^^^^^^^^^^^^^^^^^
Above, the site ``config.yaml`` only overrides specific settings in the
default ``config.yaml``. Sometimes, it is useful to *completely*
override lower-precedence settings. To do this, you can use *two* colons
at the end of a key in a configuration file. For example, if the
**site** ``config.yaml`` above looks like this:
.. code-block:: yaml
:emphasize-lines: 1
config::
install_tree: /some/other/directory
Spack will ignore all lower-precedence configuration under the
``config::`` section:
.. code-block:: console
$ spack config get config
config:
install_tree: /some/other/directory
^^^^^^^^^^^^^^^^^^^^^^
List-valued settings
^^^^^^^^^^^^^^^^^^^^^^
Let's revisit the ``config.yaml`` example one more time. The
``build_stage`` setting's value is an ordered list of directories:
**defaults**
.. code-block:: yaml
build_stage:
- $tempdir
- /nfs/tmp2/$user
Suppose the user configuration adds its *own* list of ``build_stage``
paths:
**user**
.. code-block:: yaml
build_stage:
- /lustre-scratch/$user
- ~/mystage
Spack will first look at the paths in the site ``config.yaml``, then the
paths in the user's ``~/.spack/config.yaml``. The list in the
higher-precedence scope is *prepended* to the defaults. ``spack config
get config`` shows the result:
.. code-block:: console
:emphasize-lines: 7-10
$ spack config get config
config:
install_tree: /some/other/directory
module_roots:
lmod: $spack/share/spack/lmod
build_stage:
- /lustre-scratch/$user
- ~/mystage
- $tempdir
- /nfs/tmp2/$user
$ _
As in :ref:`config-overrides`, the higher-precedence scope can
*completely* override the lower-precedence scope using `::`. So if the
user config looked like this:
**user**
.. code-block:: yaml
:emphasize-lines: 1
build_stage::
- /lustre-scratch/$user
- ~/mystage
The merged configuration would look like this:
.. code-block:: console
:emphasize-lines: 7-8
$ spack config get config
config:
install_tree: /some/other/directory
module_roots:
lmod: $spack/share/spack/lmod
build_stage:
- /lustre-scratch/$user
- ~/mystage
$ _
.. _config-file-variables:
------------------------------
Config file variables
------------------------------
Spack understands several variables which can be used in config file paths
where ever they appear. There are three sets of these variables, Spack specific
variables, environment variables, and user path variables. Spack specific
variables and environment variables both are indicated by prefixing the variable
name with ``$``. User path variables are indicated at the start of the path with
``~`` or ``~user``. Let's discuss each in turn.
^^^^^^^^^^^^^^^^^^^^^^^^
Spack Specific Variables
^^^^^^^^^^^^^^^^^^^^^^^^
Spack understands several special variables. These are:
* ``$spack``: path to the prefix of this spack installation
* ``$tempdir``: default system temporary directory (as specified in
Python's `tempfile.tempdir
<https://docs.python.org/2/library/tempfile.html#tempfile.tempdir>`_
variable.
* ``$user``: name of the current user
Note that, as with shell variables, you can write these as ``$varname``
or with braces to distinguish the variable from surrounding characters:
``${varname}``. Their names are also case insensitive meaning that ``$SPACK``
works just as well as ``$spack``. These special variables are also
substituted first, so any environment variables with the same name will not
be used.
^^^^^^^^^^^^^^^^^^^^^
Environment Variables
^^^^^^^^^^^^^^^^^^^^^
Spack then uses ``os.path.expandvars`` to expand any remaining environment
variables.
^^^^^^^^^^^^^^
User Variables
^^^^^^^^^^^^^^
Spack also uses the ``os.path.expanduser`` function on the path to expand
any user tilde paths such as ``~`` or ``~user``. These tilde paths must appear
at the beginning of the path or ``os.path.expanduser`` will not properly
expand them.
