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Create a Linux kiosk at your library

Start without a guest account

The first few steps of this process don’t actually require a guest user directory to exist, so do NOT create your guest user account yet. However, you do need to choose what your guest user account is going to be called. A reasonable account name for Don’s purposes is libraryguest. On my personal computer I call my guest account guestaccount, and I’ve used kioskguest on some installations. I avoid just the name “guest” because in modern computing the term “guest” gets used in a few other ways (such as a “guest operating system” in a virtual environment), and it’s just easier to find something unique in logs.

Choose a unique name for you guest account, but don’t create it yet. For this article, I’m using libraryguest.

Create the PostSession script

By default, GDM recognises several states: Init, PostLogin, PreSession, and PostSession. Each state has a directory located in /etc/gdm. When you place a shell script called Default in one of those directories, GDM runs the script when it reaches that state.

To trigger actions to clean up a user’s environment upon logout, create the file /etc/gdm/PostSession/Default. You can add whatever actions you want to run upon logout to the Default script. In the case of Don’s library, we wanted to clear everything from the guest’s home directory, including browser history, any LibreOffice files or GIMP files they may have created, and so on. It was important that we limited the very drastic action of removing all user data to just the guest user. We didn’t want the admin’s data to be erased upon logout, so whatever rule we added to /etc/gdm/PostSession/Default had to be limited to the guest user.

Here’s what we came up with:

#!/usr/bin/sh

echo "$USER logged out at `date`" >> /tmp/PostSession.log

if [ "X$USER" = "Xlibraryguest" ]; then

    rm -rf "$HOME"

fi

exit 0

The first line is for logging purposes. The /tmp directory gets cleared out on most distributions automatically, so we weren’t worried about creating a file that’ll grow forever and eventually crash the computer. If your distribution of choice doesn’t clean out /tmp automatically,

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