Installing a lab computer

What you do on the lab computer

Configuration of an out-of-the-box lab computer is done using an off-the-shelf Debian minimal/network install CD/DVD. This was debian-10.10.0-amd64-netinst.iso at time of writing.

1. Connect the lab computer/host to the network.
2. Boot from the install media.
3. At the installer selection menu, press the ESC key. If that doesn't give you a boot: prompt, go to step 5.
4. At the boot: prompt enter:
   • auto url=http://192.168.100.1/lab.cfg (if the host is a VM on Peter’s Mac Mini)
   • auto url=http://129.94.173.33/lab.cfg (if the host is on CSE’s K17 “trusted” subnetwork)

     and press the ENTER/RETURN key.

5. If you don't get a boot: prompt when you press the ESC key, select “Advanced options” and then choose either of the automated install options. In the fullness of time you will get a prompt where you can enter a URL. Enter the appropriate URL from the step above.
6. The screen of the computer will show the progress of the installation of both the operating system and the initial set of packages. When this initial phase is complete, the computer will reboot automatically.

   Most likely though the computer will boot again from the install media and redisplay the installer selection menu. If it does, remove the install media and reboot manually.

7. The computer should boot and display a shaded graphical login window (emphasis on “shaded”). Logging in at this stage is possible but not necessarily useful. User accounts will not be available yet and the only account which will be login-able will be root.
8. In the background the configuration engine (cfengine/cf-agent) will launch and and will start modifying configuration files in /etc and elsewhere, will start copying in files from its warehouse and will be running apt-get to install required Debian packages.
9. Towards the end of this background process, the shaded graphic login window be replaced by a monochrome (black/white) login window which mentions both “CSE” and the computer’s host name.
10. At around this point you should be able to log in with a user account and the computer will be ready for use. Rebooting will not be required.

Configuration of the process

This auth-configuration process relies on what's called a “preseed” file. See DebianInstaller → Preseed. The preseed file automatically provides answers to the questions the Debian installer would typically ask the user via the console/mouse/keyboard.

The preseed file can come from any of a range of sources, such as the install media or USB key. In our case, it comes from a local web server. This makes it easy to edit/update.

The preseed file is located in the web server’s /srv/http subdirectory, depending on the Linux distribution hosting the server (in this particular case: ArchLinux). It could be /var/www/html for Debian or CentOS/RedHat.