Relocatable Package Installers and quickpkg Update

In my book “Packaging for Apple Administrators” I show a great use of pkgbuild to wrap an application in a package installer:

$ pkgbuild --component /Applications/Numbers.app Numbers.pkg

If the application is not already in the /Applications folder, you have to add the --install-location:

$ pkgbuild --component /Volumes/Firefox/Firefox.app --install-location /Applications Firefox.pkg

This is great and wonderful, but has one drawback: the installers pkgbuild creates this way are ‘relocatable’. When the installer does not find the application in the target location, it will look if the application is installed elsewhere on the system. If it finds the ‘relocated’ application bundle, it will happily try to update it in the new location.

Usually this is not a big problem on managed systems. However, if users have copies of applications in unusual locations, e.g., because they do not have permission to install in /Applications or because they themselves are admins with dozens of versions in ~/Library/AutoPkg, then this can lead to unexpected behavior or failure.

The common solution to this is to create ‘non-relocatable’ installer packages.

What makes a pkg relocatable

The relocate element in the PackageInfo file in an installer package controls this behavior. You can see the PackageInfo file in Pacifist or with pkgutil:

$ pkgutil --expand Firefox.pkg Firefox_expanded
$ more Firefox_expanded/PackageInfo 

Among much other data you will see this xml element:

<relocate>
    <bundle id="org.mozilla.firefox"/>
</relocate>

This tells the Installer to look for an application bundle with the given identifier and install in that location. To disable this, you can replace the above element with an empty relocate element:

<relocate/>

Then installer will install or upgrade in the given install-location (e.g. /Applications) only.

You can apply this change to the expanded PackageInfo file with a text editor and re-create the pkg file with

$ pkgutil --flatten Firefox_expanded/ Firefox-nr.pkg

(‘nr’ for ‘non-relocatable’)

However, applying these steps after creating each package is tedious and error-prone, so we want to look for a better solution.

Telling pkgbuild to not re-locate

The pkgbuild man page mentions there is an option to create non-relocatable installer pkgs with the BundleIsRelocatable option in a ‘component property list’. This is great, since it is better to use documented options, rather than hacking the PackageInfo directly. However, to use the --component-plist option with pkgbuild you have to use the --root option rather than the --component option This requires a bit more effort.

First create a project folder:

$ mkdir -p Firefox/payload
$ cd Firefox

And copy the application to the payload directory:

$ cp -R /Volumes/Firefox/Firefox.app payload/

Then you can use pkgbuild’s --analyze to create a template component property list:

$ pkgbuild --analyze --root payload Firefox-component.plist
pkgbuild: Inferring bundle components from contents of payload
pkgbuild: Writing new component property list to Firefox-component.plist

You can then open the generated property list file in a text or property list editor. You will see several values for different settings and a list of ChildBundles. Change the value of the BundleIsRelocatable key from <true/> to <false/>. You can do this in the editor or with the plutil command:

$ plutil -replace BundleIsRelocatable -bool NO Firefox-component.plist

Then build the package with pkgbuild:

$  pkgbuild --root payload --identifier org.mozilla.firefox --version 53.0.3 --install-location /Applications --component-plist Firefox-component.plist Firefox-53.0.3.pkg

This will build the package installer with an empty relocate element.

Note: munki-pkg has an option suppress-bundle-relocation which achieves the same result.

QuickPkg

This approach can be useful but is still complicated. To simplify the creation I have updated my quickpkg tool to create non-relocatable packages by default. You can change the new default behavior with the --relocatable option.

$ quickpkg ~/Downloads/Firefox\ 53.0.3.dmg 
Firefox-53.0.3.pkg

Enjoy!

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