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Last modified: 22 August 2023


System Requirements

CIAO is supported on a number of operating systems, which are listed on the Platform Support page. Certain system requirements are necessary to successfully install and run CIAO.

Installation requirements: conda

When using conda to install CIAO, the conda command-line tool must be present, and be at least version 4.7.6:

$ conda --version
conda 4.10.3

If the command does not exist then the miniconda package can be installed from the Anaconda website, and if the version is too low then it can be updated with

$ conda update conda

macOS users must use the Intel x86_64 version of conda, as we currently do not support the ARM64 version.

Installation requirements: ciao-install

For CIAO installation by the ciao-install script, available from the download page. This script requires bash to run it, and either curl or wget to download the binary packages. The gzip tool is required to uncompress the binary packages, and tar to unpack them.

Memory and Disk Space

Chandra data files are large, which implies that certain processing and analysis operations will work more efficiently when they have access to large amounts of RAM. We recommend a minimum of 4Gb main memory. A full CIAO installation, including the background calibration files will require ~15Gb of disk space. The disk space for individual observations varies from a few megabyte to several gigabytes depending on the target as well as the exposure time and instrument configuration.


Pre-built binaries for CIAO 4.15.2 are built for Linux on CentOS 7 machines. These are expected to be compatible with most recent Linux distributions, but may not work with old versions.


X11, the X window system.

Apple macOS

Pre-built binaries for CIAO 4.15.2 for macOS were built on macOS 10.15 (Catalina) Intel chip, and are compatible with newer versions through macOS 13 (Ventura), both Intel and ARM (M1 and M2) chips via Rosetta2. At the moment, conda users must use the Intel x86_64 version, as we currently do not support the ARM64 version.

Visit our platform support page for our statement about support for macOS 11 and 12 with the M1 chip. .


X11 must be installed from the XQuartz website. Users must be using XQuartz version 2.7.11 or newer.

Some users have reported problems related to disappearing menus using ds9 with Xquartz version 2.8.5 which was released on January 26, 2023. This appears to be a bug in that version of Xquartz; users are advised to downgrade to version 2.8.4 to mitigate the problem.


CIAO requires users have the Apple's Xcode tools installed on OSX/macOS. These tools are needed during the installation process to configure the programs to run on users machine.

X11 System Libraries


These steps are normally not needed for users of a conda-install of CIAO.

CIAO requires several X11 related system libraries to be installed. These are usually already installed on most end-user Linux machines; however, they are frequently omitted when running on "headless" clusters and Apple users need to install XQuartz separately.

Users are responsible for installing them via the package manager (e.g. yum, fink).

The names may differ slightly but here are the known packages:

Doing an ldd on our executables and libraries will produce a list something like the following list of system libaries that will either be located in /lib or /usr/lib.