Before installing IRIX/IRAF, one must 1) obtain an appropriate IRIX/IRAF distribution, e.g., from the IRAF network archive on iraf.noao.edu (one of it's mirror sites, or by ordering a tape or CD-ROM distribution from NOAO), 2) select the server or node on which the system is to be installed and arrange for sufficient disk space to hold the system, and 3) set aside sufficient time to do the installation. If these directions are followed carefully and mistakes are avoided the basic installation should only take a few minutes on a fast machine. Additional time may be required to customize the system, to configure the local tape drives and other devices, set up IRAF networking, and so on.
The amount of disk space required to install a full IRAF system depends upon the system configuration, including the number of layered packages installed on top of the core IRAF system. The main system, including both the core IRAF system and NOAO package sources, requires approximately 177 Mb. See the IRIX/IRAF README for more information on installation options.