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Specifying Install Operations

In managed installs, install operations allow you to configure the destination environment before the payload is copied to the file system and to perform additional processing afterward. To specify install operations, you use executable files (known as install operation executables) that Installer invokes at specific stages during an install, as described in The Installation Process.

Install operation executables must be named according to the install operation you want to define. The files can be binary files or text files containing shell scripts. All install operations are optional. You define only the operations required by a packaged product.

This chapter shows how you use install operation executables to define the install operations the Installer application performs in a managed install.

Overview of Install Operations

After the Installer application finishes checking installation requirements, it performs an install through distinct operations, known as install operations. You can define all but one of these operations, which copy payloads to their installation destinations. You should not use install operations to fix install problems, such as incorrect ownership and access permissions. You should use install operations only when other managed-install features, such as installation requirements, are not adequate for the chore you need to perform as part of installing a package or metapackage.

Table 7-1 lists the install operations in the order Installer performs them.

**Table 7-1** Install operations and executables
Install operation	Operation executable	Description
Preflight	`preflight`	Prepares the target system for the install; for example, quitting or stopping specific applications or processes.
Preinstall	`preinstall`	Prepares the target system for a payload for which no receipt is found.
Preupgrade	`preupgrade`	Prepares the target system for a payload for which a receipt is found.
Payload Drop	None	Copies the payload to the installation destination. This operation is not modifiable.
Postinstall	`postinstall`	Cleanup or system setup for an installed payload.
Postupgrade	`postupgrade`	Cleanup or system setup for an upgraded payload.
Postflight	`postflight`	Install postprocessing; for example, setting up `cron(8)` jobs or launching the installed application.

The first three install operations, Preflight, Preinstall, and Preupgrade, can stop an install. When one of the corresponding executables returns anything other than 0, Installer cancels the install.

Arguments and Environment Variables for Install Operations

The following list describes the arguments and environment variables available to install operation executables. Note that not all environment variables are available to all executables (see Table 7-2).

$1: Full path to the installation package the Installer application is processing. For example:
/Volumes/Users/michelle/Desktop/Levon.mpkg
$2: Full path to the installation destination. For example:
/Applications
$3: Installation volume (or mountpoint) to receive the payload. For example:
/
/Volumes/Tools
$4: The root directory for the system:
/
$SCRIPT_NAME: Filename of the operation executable. For example:
preflight
$PACKAGE_PATH: Full path to the installation package. Same as $1.
$INSTALLER_TEMP: Scratch directory used by Installer to place its temporary work files. Install operations may use this area for their temporary work, too, but must not overwrite any Installer files. The Installer application erases this directory at the end of the install. For example:
/private/tmp/.Levon.pkg.897.install
$RECEIPT_PATH: Full path to a temporary directory containing the operation executable. This is a subdirectory of $INSTALLER_TEMP. This location may vary between installs. The executable can use this path to locate other files in the package. For example:
/private/tmp/.Levon.pkg.897.install/Receipts/Levon.pkg/Contents/Resources

The four arguments described earlier are available to all install operations. Table 7-2 shows the availability of the environment variables.

**Table 7-2** Environment variables in operation executables
Operation executable	Available environment variables
`preflight`	None.
`preinstall`, `preupgrade`	`$SCRIPT_NAME`, `$PACKAGE_PATH`, `$INSTALLER_TEMP`.
`postinstall`, `postupgrade`, `postflight`	`$SCRIPT_NAME`, `$INSTALLER_TEMP`, `$PACKAGE_PATH`, `$RECEIPT_PATH`.

Example: Install Operation Script

Listing 7-1 shows a postflight operation implemented as a shell script that launches an installed application.

Listing 7-1 Sample install operation script

#!/bin/sh

echo $SCRIPT_NAME: launching Levon.app

open -b com.mycompany.Levon

exit 0

After Installer executes this install operation script, its log shows an entry similar to the one in Listing 7-2.

Listing 7-2 Sample Installer log entry

Jun 20 13:30:03 Athene : postflight[2274]: postflight: launching Levon.app

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