.. _config-yaml:
====================================
Basic settings in ``config.yaml``
====================================
Spack's basic configuration options are set in ``config.yaml``. You can
see the default settings by looking at
``etc/spack/defaults/config.yaml``:
.. literalinclude:: ../../../etc/spack/defaults/config.yaml
:language: yaml
These settings can be overridden in ``etc/spack/config.yaml`` or
``~/.spack/config.yaml``. See :ref:`configuration-scopes` for details.
.. _config-file-variables:
------------------------------
Config file variables
------------------------------
You may notice some variables prefixed with ``$`` in the settings above.
Spack understands several variables that can be used in values of
configuration parameters. They are:
* ``$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}``.
--------------------
``install_tree``
--------------------
The location where Spack will install packages and their dependencies.
Default is ``$spack/opt/spack``.
---------------------------------------------------
``install_hash_length`` and ``install_path_scheme``
---------------------------------------------------
The default Spack installation path can be very long and can create
problems for scripts with hardcoded shebangs. There are two parameters
to help with that. Firstly, the ``install_hash_length`` parameter can
set the length of the hash in the installation path from 1 to 32. The
default path uses the full 32 characters.
Secondly, it is
also possible to modify the entire installation scheme. By default
Spack uses
``${ARCHITECTURE}/${COMPILERNAME}-${COMPILERVER}/${PACKAGE}-${VERSION}-${HASH}``
where the tokens that are available for use in this directive are the
same as those understood by the ``Spec.format`` method. Using this parameter it
is possible to use a different package layout or reduce the depth of
the installation paths. For example
.. code-block:: yaml
config:
install_path_scheme: '${PACKAGE}/${VERSION}/${HASH:7}'
would install packages into sub-directories using only the package
name, version and a hash length of 7 characters.
When using either parameter to set the hash length it only affects the
representation of the hash in the installation directory. You
should be aware that the smaller the hash length the more likely
naming conflicts will occur. These parameters are independent of those
used to configure module names.
.. warning:: Modifying the installation hash length or path scheme after
packages have been installed will prevent Spack from being
able to find the old installation directories.
--------------------
``module_roots``
--------------------
Controls where Spack installs generated module files. You can customize
the location for each type of module. e.g.:
.. code-block:: yaml
module_roots:
tcl: $spack/share/spack/modules
lmod: $spack/share/spack/lmod
dotkit: $spack/share/spack/dotkit
See :ref:`modules` for details.
--------------------
``build_stage``
--------------------
Spack is designed to run out of a user home directories, and on many
systems the home directory a (slow) network filesystem. On most systems,
building in a temporary filesystem results in faster builds than building
in the home directory. Usually, there is also more space available in
the temporary location than in the home directory. So, Spack tries to
create build stages in temporary space.
By default, Spack's ``build_stage`` is configured like this:
.. code-block:: yaml
build_stage:
- $tempdir
- /nfs/tmp2/$user
- $spack/var/spack/stage
This is an ordered list of paths that Spack should search when trying to
find a temporary directory for the build stage. The list is searched in
order, and Spack will use the first directory to which it has write access.
See :ref:`config-file-variables` for more on ``$tempdir`` and ``$spack``.
When Spack builds a package, it creates a temporary directory within the
``build_stage``, and it creates a symbolic link to that directory in
``$spack/var/spack/stage``. This is used totrack the stage.
After a package is successfully installed, Spack deletes the temporary
directory it used to build. Unsuccessful builds are not deleted, but you
can manually purge them with :ref:`spack purge --stage
<cmd-spack-purge>`.
.. note::
The last item in the list is ``$spack/var/spack/stage``. If this is the
only writable directory in the ``build_stage`` list, Spack will build
*directly* in ``$spack/var/spack/stage`` and will not link to temporary
space.
--------------------
``source_cache``
--------------------
Location to cache downloaded tarballs and repositories. By default these
are stored in ``$spack/var/spack/cache``. These are stored indefinitely
by default. Can be purged with :ref:`spack purge --downloads
<cmd-spack-purge>`.
--------------------
``misc_cache``
--------------------
Temporary directory to store long-lived cache files, such as indices of
packages available in repositories. Defaults to ``~/.spack/cache``. Can
be purged with :ref:`spack purge --misc-cache <cmd-spack-purge>`.
--------------------
``verify_ssl``
--------------------
When set to ``true`` (default) Spack will verify certificates of remote
hosts when making ``ssl`` connections. Set to ``false`` to disable, and
tools like ``curl`` will use their ``--insecure`` options. Disabling
this can expose you to attacks. Use at your own risk.
--------------------
``checksum``
--------------------
When set to ``true``, Spack verifies downloaded source code using a
checksum, and will refuse to build packages that it cannot verify. Set
to ``false`` to disable these checks. Disabling this can expose you to
attacks. Use at your own risk.
--------------------
``dirty``
--------------------
By default, Spack unsets variables in your environment that can change
the way packages build. This includes ``LD_LIBRARY_PATH``, ``CPATH``,
``LIBRARY_PATH``, ``DYLD_LIBRARY_PATH``, and others.
By default, builds are ``clean``, but on some machines, compilers and
other tools may need custom ``LD_LIBRARY_PATH`` setings to run. You can
set ``dirty`` to ``true`` to skip the cleaning step and make all builds
"dirty" by default. Be aware that this will reduce the reproducibility
of builds.
