...
There is a number of built-in conditions which are statically pre-set on launching the installation and which can be only referenced by their ID:
izpack.aixinstall
True if the current OS is (any) IBM AIX.izpack.windowsinstall
True if the current OS is (any) Windows.izpack.windowsinstall.xp
True if the current OS is Windows XP.izpack.windowsinstall.2003
True if the current OS is Windows Server 2003.izpack.windowsinstall.vista
True if the current OS is Windows Vista.izpack.windowsinstall.7
True if the current OS is Windows 7.izpack.windowsinstall.8
True if the current OS is Windows 8.izpack.windowsinstall.10
True if the current OS is Windows 10.izpack.macinstall
True if the current OS is Mac OS..izpack.macinstall.osx
True if the current OS is Mac OS X.izpack.linuxinstall
True if the current OS is (any) Linux.izpack.solarisinstall
True if the current OS is (any) Solaris.izpack.solarisinstall.x86
True if the current OS is (any) Solaris x86.izpack.solarisinstall.sparc
True if the current OS is (any) Solaris Sparc.
...
where <packname> is the name attribute of the according pack. If the appropriate pack <pack name="..."> defined in the installation description is selected, the condition validates true. Packs can be selected either in unattended installations by replaying a record of a previous installation (auto-install.xml) or interactively by the user by means of PacksPanel or its derivates, ImgPacksPanel or TreePacksPanel.