St. Ignatius College Prep Tech Blog

Method #1: Use a Logout Hook

Why you might not want to use the logout hook

Apple deprecated the login/logout hooks as of Mac OS X 10.4 (Tiger), and—as of this writing—we're up to OS X 10.10 (Yosemite), and the hooks still work. In theory, though, Apple could yank support for the login/logout hooks at any time.

Credit where credit is due...

If you'd like to use a logout hook, this is what you do (credit to How to delete Keychains at logout for being the basis of these instructions).

Instructions

Make a location for your script

Amsys recommends creating one special for your organization (they use /Library/amsys, and we would use /Library/siprep), so create one appropriate for your organization.

In the terminal, you can create that directory using this command:

Make your script

To make the script, you can use the graphical text editor of your choice (e.g., TextWrangler or Sublime Text). If you prefer Mac OS X's built-in TextEdit, just be sure you're saving as plain text and not rich text format. Just remember, once you copy the script to /Library/nameofyourorg, that you need to change ownership of the file to root (owner) and wheel (group).

A simple way to use the terminal to make the script (and avoid having to change ownership of the file later) is to just use the built-in text editor, nano:

Then, paste in this code:

Then save (Control-X).

Amsys had $USER instead of $1, but I couldn't get the script to work unless I used $1.

Make the script executable

Whether you used a graphical text editor or a terminal based one, you'll still want to change the permissions on the file so anyone can execute it:

Add your script to the logout hook

To get the logout to invoke your script, use this command

Method #2: Use a Launch Daemon at boot time

Introduction

This second method uses a Launch Daemon (which is not deprecated), but it also assumes you will reboot the machine from time to time (for example, if you have your machines scheduled to reboot every night or every weekend).

The advantage, of course, is that if Apple decides to no longer support the logout hook, this method will likely still work. The disadvantage is that this will work only when you reboot the machine and not every time a user logs out.

I haven't found a way to successfully create a launchd process that executes at logout (instead of just login). someone on Stack Exchange claims to have been able to do it, but I couldn't replicate those steps with success.

So what this does is, at boot time at a system level, just delete all user keychains.

Instructions

Create the shell script

Similarly to the other method, we're going to create (if it doesn't already exist yet), a custom directory for your organization:

Then make the script (again, you can do this in your favorite graphical text editor, move it over to the directory, and then change ownership to root user and wheel group, but this is a fairly straightforward way to do it one fell swoop without having to change ownership later):

In the text editor, paste in:

Then save (Control-X).

Make it executable

Create the Launch Daemon

You're going to create a custom .plist file

In the text editor, put in:

Save the file (Control-X) and reboot.