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The Installation Process

After the Installer application opens a package, it performs the installation process in several phases:

• Requirements Check

  Installer ensures that the installation host meets the system and volume requirements specified by the package.

• Preinstall

  Installer runs preflight and preinstall/preupgrade executables. If an executable returns anything other than 0, the install is cancelled.

• Install

  Installer extracts the payload of component packages and copies it to the appropriate destinations.

• Save Receipt

  Installer copies the component package file (with its payload stripped) to the Library/Receipts directory in the installation volume.

• Postinstall

  Installer runs postinstall/postupgrade and postflight executables.

The following sections detail the operations that the Installer application performs in the Requirements Check, Preinstall, and Postinstall phases of the installation process for the three types of installation package files. For details on the purpose of the executable files used to define installation requirements and install operations (InstallationCheck, VolumeCheck, preflight, preinstall, preupgrade, postinstall, postupgrade, and postflight), see “Specifying Install Operations” and “Specifying System and Volume Requirements in Pre-Tiger Systems.”

In this section:

Component Package Installation Process
Metapackage Installation Process
Distribution Package Installation Process

Component Package Installation Process

This is how Installer performs the Requirements Check, Preinstall, and Postinstall phases of a component package’s installation process:

• Requirements Check

  InstallationCheck

  VolumeCheck on each available volume

• Preinstall

  preflight

  preinstall or preupgrade

• Postinstall

  postinstall or postupgrade

  postflight

Metapackage Installation Process

This is how the Installer application performs the Requirements Check, Preinstall, and Postinstall phases of a metapackage’s installation process:

• Requirements Check

  InstallationCheck for each package but not the top metapackage

  VolumeCheck on each available volume for each package but not the top metapackage

• Preinstall

  preflight for top metapackage

  preflight for each package

  preinstall or preupgrade for top metapackage

  preinstall or preupgrade for each package

• Postinstall

  postinstall or postupgrade for each package

  postinstall or postupgrade for top metapackage

  postflight for top metapackage

  postflight for each package

Distribution Package Installation Process

This is how the Installer application performs the Requirements Check, Preinstall, and Postinstall phases of a distribution package’s installation process:

• Requirements Check

  Installation Check script

  Volume Check script on each available volume

• Preinstall

  preflight for each package

  preinstall or preupgrade for each package

• Postinstall

  postinstall or postupgrade for each package

  postflight for each package

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