To understand what a probe keyword is, you first need to recall what a rule keyword is. A rule keyword is a predefined lexical unit or word that describes a general system attribute, such as host name, hostname, or memory size, memsize. Rule keywords and the values that are associated with them enable you to match a system that has the same attribute to a profile. This match of a system's attributes defines how the Solaris software is to be installed on each system in the group.
Custom JumpStart environment variables, which you use in begin and finish scripts, are set on demand. For example, information about which operating system is already installed on a system is only available in SI_INSTALLED after the installed rule keyword is used.
In some situations, you might need to extract the same information in a begin or finish script for a purpose other than to match a system and run a profile. Probe keywords provide the solution. Probe keywords extract attribute information and remove the need for you to set up a matching condition and run a profile.
For a list of probe keywords and values, see Probe Keywords and Values.