Routines for handling the runtime configuration and external data dependencies in CASA. These functions are needed to manipulate the runtime data necessary for proper CASA operation.


List available casarundata versions on CASA server at


Check for updates to the installed casarundata and install the update or change to the requested version when appropriate.


Use measurespath, data_auto_update, and measures_auto_update from configDict to do any auto updates as necessary.


Get configuration values as a list of strings which can be logged, stored, or evaluated.


Get the summary information on the 3 types of data managed by casaconfig.


List available measures versions on the ASTRON server


Update or install the IERS data used for measures calculations from the ASTRON server at path.


Pull the casarundata contents from the CASA host and install it in path.


Set the path in .casarc to the desired data directory


Update the data contants at path to the most recently released versions of casarundata and measures data.

configuration values
from casaconfig import config

Each modular CASA package as well as the full monolithic installation reads a set of configuration files to set the CASA runtime options. The configuration is set when config is imported from casaconfig. The configuration files include the default values (provided by casaconfig), an optional site configuration file, and an optional user configuration file.

The optional user configuration file is found in their home .casa folder as (~/.casa/

The optional site configuration file is found in a number of different ways (the first found is the one used):

  • as given by the CASASITECONFIG environment variable

  • /opt/casa/

  • /home/casa/

  • found anywhere within sys.path following the usual python import rules.

Note: when CASASITECONFIG is set then that is the only location used for the site configuration file. If that path does not exist then a warning message is printed and no attempt is made to find a site configuration file at any other location. Execution then continues without using any site configuration file.

The user configuration file is ignored when --noconfig is used on the command line.

The site configuration file is ignored when --nositeconfig is used on the command line.

An alternative path to the user configuration file can be given using the --configfile <path_to_file> option on the command line.

The configuration files are used in order of defaults, site configuration, user configuration. The optional configuration files need only set parameters that differ from the defaults. The resulting configuration will always include the full set of configuration parameters recognized by CASA. The configuration files are evaluated python files so any valid python can be used.

On import, the dict of config values also contains 2 functions: load_success and load_failure. load_success returns a list of config file paths used when config was imported, in the order they were used. load_failure returns a dictionary of exceptions encountered by config file when loading that config file (and then that config file is not found in the list returned by load_success).

Note: configuration happens before any parts of CASA are loaded so no CASA modules should be used within the configuration steps.

Note: during use of the configuration process in module execution (the “-m” python option, used by “casa” startup and the casaconfig command line for example) all print output is suppressed so that it does not interfere with module initialization.

Use the get_config() function to get a list of strings showing the configuration parameters with values.

Note: all path configuration values are expanded using expanduser and abspath.

The following parameters can be set in a configuration file. Many of these parameters can be set or ignored through the casashell command line options. The default values are also shown here.

  • datapath : list of paths where CASA should search for data subdirectories. Default [measurespath].

  • measurespath : location of required measures data, takes precedence over any measures data also present in datapath. Default “~/.casa/data”.

  • measures_auto_update : when True, casatools uses measures_update() to update the measures data as necessary when casatools starts. See measures_update() for additional details. Default True.

  • data_auto_update : when True, casatools uses data_update() followed by measures_update() to update the reference AND measures data. See data_update() and measures_update() for additional details. Default True.

  • startupfile : path to a python script used at startup by casashell when present. Default “~/.casa/”.

  • cachedir : location of the directory where ipython writes information (history, etc), also the location of the rc file used by the casaviewer. Default “~/.casa”.

  • logfile : log file path/name. Default “casa-yyyymmdd-hhmmss.log”. Note that this default value is set using gmtime() from the time module on import of config.

  • nologfile : do not create a log file when True, default False. If nologfile is True, then any logfile value is ignored and there is no log file.

  • log2term : print log output to terminal when True (in addition to any logfile and CASA logger), default False.

  • nologger : do not start the CASA logger GUI when True, default False.

  • nogui : avoid starting GUI tools when True, default False. If nogui is True then the CASA logger is not started even if nologger is False.

  • colors : the IPython prompt color scheme. Must be one of “Neutral”, “NoColor”, “Linux” or “LightBG”, default “Neutral”. If an invalid color is given a warning message is shown but CASA continues using the default color.

  • agg : startup without a graphical backend if True, default False.

  • pipeline : attempt to load the pipeline modules and set other options appropriate for pipeline use if True, default False. When pipeline is True then agg will be assumed to be True even if agg is set to False here or on the command line.

  • iplog : create and use an IPython log if True, default False.

  • iplogfile : IPython log file path/name, used only when iplog is True. Default “ipython-yyyymmdd-hhmmss.log”. Note that this default value is set using gmtime() from the time module on import of config.

  • user_site : include the user’s local site-packages in the python path if True. Normally these should be excluded to avoid potential conflicts with CASA modules. Default False.

Note: The auto update parameters are used during casatools initialization.

Note: It is an error for measures_auto_update to be False when data_auto_update is True. In that case no auto updates will happen and CASA will continue after printing out an error message.

This example user configuration has a measurespath that is different from the default of “~/.casa/data”, turned off auto updates, turned off the GUI logger, and print logger output to the terminal.

data_auto_update = False
measures_auto_update = False

Distribtions of casa do not come with the required casarundata, expected at measurespath. The casaconfig module provides functions to install and maintain that data.

A monolithic CASA site installation will typically provide a that sets measurespath to a shared data location and sets data_auto_update and measures_auto_update to False (the site is then responsible for regularly updating that data and individual users will not be able to do that).

Individual users may chose to install and maintain their own copy of the casarundata installed at measurespath. The installed size of casarundata is about 830MB. If that location exists and is empty when casa starts (the casatools module is initialized) and the auto update config values are True (the default) then the casarundata will be installed at measurespath automatically. Future use of casa (the casatools module) will keep that location up to date as new measures data becomes available (daily) or new data is available (a few times a year). Users of a site installation of casa may chose to install and maintain their own copy of the casarundata because they may want to control exactly when that data is updated/

Note that the default logfile and the default iplogfile use the time module to set the value to a string that depends on when the config file is evaluated.

See “ExternalData” for additional details.

Site installations may choose to maintain a site configuration file. The usual name for that file is although any name is possible when using the CASASITECONFIG environment variable.

When present, this file is evaluated after the default configuration values are set and before any user’s is used. The site configuration file is ignored when the --nositeconfig command line option is used.

A site installation may provide a site configuration file that sets measurespath to the location of casarundata that can be shared by multiple users. The site would then turn off auto updates for that installation and regular updates of the data is then done by the site administrators. An example site configuration file, found at private/ in the casaconfig module, is shown below. The measurespath value in this example should be edited to be the path where the site has installed casarundata.

# An example site config file.
# Place this in a location checked by casaconfig:
#  /opt/casa/
#  /home/casa/
#  the environment value CASASITECONFIG - use the fully qualified path
#  anywhere in the python path, e.g. the site-packages directory in the CASA being used

# This file should be edited to set measurespath as appropriate

# Set this to point to the location where the site maintained casarundata can be found
# by default datapath will include measurespath

measurespath = "/path/to/installed/casarundata"

# turn off all auto updates of data

measures_auto_update = False
data_auto_update = False

When config is imported from the casaconfig module it will search for a site configuration file by first checking to see if the CASASITECONFIG environment value is set. If that value is set then it will use that value as the location of the site configuration file. If that value is not set then it looks for a at “/opt/casa”, “/home/casa” or anywhere in the python path. It uses the first site configuration file found.

Note: If CASASITECONFIG is set and that value is not a path to an existing file then a warning message is printed and the configuration continues without using any site configuration file (none of the other possible locations are checked if CASASITECONFIG is set).

Site data can be shared across multiple CASA installations. The site administrators are responsible for installing the CASA data and keeping it up to date. Methods provided by casaconfig should be used to populate that location (update_all() or pull_data()) and keep it up to date (data_update() or measures_update() or --update_all casaconfig module command-line option.

Auto updates are turned off in a site configuration file because the site data location should not be updated by individual users (auto updates also require that the user own meausurespath, which is not typical for a site installation).

Note measurespath must be set to some valid location when CASA starts. For monolithic CASA, when measurespath is set to a location that does not exist it will exit with a message that it needs to be set.

Individual users using a site installation may choose to have their own casarundata installed (e.g. they may wish to control when the data upates happen or they may wish to use an older version of the casarundata). Users can do that by setting measurespath to a personally controlled location in their personal configuration file (typically at ~/.casa/

This section only applies to the monolithic/tar-file CASA distribution

The '' file found at the startupfile configuration value (defaults to ~/.casa/ is evaluated by the CASA shell just before the CASA prompt is presented to the user. This allows users to customize their CASA shell environment beyond the standard settings in '', by importing packages, setting variables or modifying the python system path. The startup file is optional. It can be ignored by setting startupfile in their configuration file to indicate a path that does not exist or by using the --nostartupfile casashell command line option.

One case where this is useful is for configuring CASA for ALMA data reduction. A package called 'analysisUtils' is often used as part of ALMA analysis. It is typically imported and instantiated in

$ cat ~/.casa/

import sys, os
import analysisUtils as aUes = aU.stuffForScienceDataReduction()

In this example, the standard python modules os and sys are made available in the CASA shell. The path where the analysisUtils module can be found is added to the Python system path, and finally the package is imported and an object is created. These modules and objects will then be available for the user within the CASA shell environment.

casa command line

casa(-h, --help, --configfile, ---noconfig, --nositeconfig, --startupfile, --nostartupfile, --logfile, --log2term, --nologger, --nologfile, --nogui, --cachedir, --colors, --pipeline, --agg, --iplog, --datapath, --reference-testing, --no-auto-update, --user-site, -v, --version, -c)

With the full installation of CASA (monolithic CASA), the python environment itself is included and started through <CASA_installation_Path>/bin/casa. This <CASA_installation_path>/bin/casa executable can be provided the following options to change configuration values at run time:

-h, --help               show this help message and exit
--configfile CONFIGFILE  location of the user configuration file
--noconfig               do not load user configuration file
--nositeconfig           do not load site configuration file
--startupfile STARTFILE  path to user's startup file
--nostartupfile          do not use any startup file
--logfile LOGFILE        path to log file
--log2term               direct output to terminal
--nologger               do not start CASA logger
--nologfile              do not create a log file
--nogui                  avoid starting GUI tools
--cachedir CACHEDIR      location for internal working files
--colors {Neutral,NoColor,Linux,LightBG} prompt color
--pipeline               start CASA pipeline run
--agg                    startup without graphical backend
--iplog                  create ipython log
--datapath DATAPATH      data path(s) [colon separated]
--reference-testing      force *measurespath* to contain the casarundata when this version was produced, used for testing purposes
--no-auto-update         turn off all auto updates
--user-site              include user's local site-packages lib in path
-v, --version            show CASA version
-c ...                   python eval string or python script to execute

These options take precedence over the configuration files.

The --configfile option is used to provide an alternative path to the user’s configuration file. When that option is used the file at that location is used instead of the default user configuration file (~/.casa/ The --noconfig option turns off all use of the user’s configuration file. If --configfile and --noconfig file are used at the same time, the user’s configuration file is ignored and a warning message is printed.

The --nostartupfile option is provided as a way to turn off loading of the startup file, That can also be done by setting startupfile to a non-existant file or empty string in a configuration file. If --startupfile and --nostartupfile are used at the same time no startup file is used and a warning message is printed.

The --reference-testing option is provided to help testers ensure that a known casarundata is installed in measurespath before CASA starts. Use of this option turns off all auto updates.

The --no-auto-update option turns off any automatic data updates even if data_auto_update or measures_auto_update are True.

Note: The casaviewer instance launched from within interactive tclean will not inherit these casa command line arguments. Consequently, interactive tclean in CASA 6.6.4 requires either ~/.casa/, ~/.casa/data or a locatable in order to run properly.

casaconfig command line

casaconfig(-h, --help, --configfile, ---noconfig, --nositeconfig, --measurespath, --pull-data, --data-update, --measures-update, --update-all, --reference-testing, --current-data, --summary, --force)

The casaconfig module may be used by itself with these options. The full set of config files are first used (except as omitted by the options) then the options are used and then python exits.

For all of the update options the most recent version is assumed and the force argument is False. These are NOT auto updates so the auto update rules do not apply. If the user has permission to update that data then that data will be updated if a new version is found.

The casaconfig module can be used to initially populate a measurespath location with data or to update it or to check on the status of a measurespath. Note that unlike the auto update rules, measurespath need not already exist before it’s used here.

python -m casaconfig .. options ...
-h, --help                  show this help message and exit
--configfile CONFIGFILE     location of the user configuration file
--noconfig                  do not load user configuration file
--nositeconfig              do not load site configuration file
--measurespath MEASUREPATH  location of casarundata
--pull-data                 invoke pull_data() to populate measurespath with the latest casarundata
--data-update               invoke data_update() to update measurespath to the latest casarundata
--measures-update           invoke measures_update() to update measurespath to the latest measures data
--update-all                invoke update_all() to populate (update) measurespath with the latest casarundata and measures data.
--reference-testing         set measurespath to contain the casarundata when this version was produced, used for testing purposes
--current-data              print out a summary of the current casarundata and measures data installed in measurespath and then exit.
--summary                   print out a summary of casaconfig data handling and exit
--force                     force an update using the force=True option to update_all, data_update, and measures_update

For a monolithic CASA installation the python to use on the command line is the one that is packaged in the bin directory with the casa script and is typically python3. For modular casa the python should be the one with the environment containing the installed casaconfig module.

The --configfile option is used to provide an alternative path to the user’s configuration file. When that option is used the file at that location is used instead of the default user configuration file (~/.casa/

The --noconfig option turns off all use of any user’s configuration file. If –configfile and –noconfig file are both used then the user’s configuration file is ignored and a warning message is printed.

The --nositeconfig option turns off all use of any site configuration file.

The --measurespath option allows the user to specify the path to the data for use by the data related options. This overrides the value of measurespath in the configuration files.

The data related options (--pull-data,--data-update, --measures-update, and --update-all) use measurespath without explicitly setting the version string. The force parameter remains False as does the auto_update_rules parameter. This means that if a new version exists and the user has read and write permissions in measurespath then an update will happen as if those functions were used from a python session.

When the --current-data option is used no updates happen even if those options are also used.

The --reference-testing option can not be used with --pull-data, --data-update, --measures-update, and --update-all.

The --summary option summarizes the configuration steps. It shows the paths to the loaded config files (default first, then any optional site configuration file, and finally any user configuration file). Any errors when loading each configuration file are then shown (files with errors are not loaded and will not show up in the list of loaded files). The measurespath set by those configure steps is shown. Finally the version strings for casarundata and measures are shown as are the release version strings if available (these are only available for monolithic casa installations). This option can be useful when debugging and testing configuration files.

The --force option can be used to force casaconfig to check for updates (and install any that are available) when the normal once-a-day checking rules might have caused it to not update measurespath.

Note that if measurespath does not exist then --pull-data, --update-all, and --reference-testing will create it before populating it.