Petter Reinholdtsen

Debian Jessie, PXE and automatic firmware installation
17th October 2014

When PXE installing laptops with Debian, I often run into the problem that the WiFi card require some firmware to work properly. And it has been a pain to fix this using preseeding in Debian. Normally something more is needed. But thanks to my isenkram package and its recent tasksel extension, it has now become easy to do this using simple preseeding.

The isenkram-cli package provide tasksel tasks which will install firmware for the hardware found in the machine (actually, requested by the kernel modules for the hardware). (It can also install user space programs supporting the hardware detected, but that is not the focus of this story.)

To get this working in the default installation, two preeseding values are needed. First, the isenkram-cli package must be installed into the target chroot (aka the hard drive) before tasksel is executed in the pkgsel step of the debian-installer system. This is done by preseeding the base-installer/includes debconf value to include the isenkram-cli package. The package name is next passed to debootstrap for installation. With the isenkram-cli package in place, tasksel will automatically use the isenkram tasks to detect hardware specific packages for the machine being installed and install them, because isenkram-cli contain tasksel tasks.

Second, one need to enable the non-free APT repository, because most firmware unfortunately is non-free. This is done by preseeding the apt-mirror-setup step. This is unfortunate, but for a lot of hardware it is the only option in Debian.

The end result is two lines needed in your preseeding file to get firmware installed automatically by the installer:

base-installer base-installer/includes string isenkram-cli
apt-mirror-setup apt-setup/non-free boolean true

The current version of isenkram-cli in testing/jessie will install both firmware and user space packages when using this method. It also do not work well, so use version 0.15 or later. Installing both firmware and user space packages might give you a bit more than you want, so I decided to split the tasksel task in two, one for firmware and one for user space programs. The firmware task is enabled by default, while the one for user space programs is not. This split is implemented in the package currently in unstable.

If you decide to give this a go, please let me know (via email) how this recipe work for you. :)

So, I bet you are wondering, how can this work. First and foremost, it work because tasksel is modular, and driven by whatever files it find in /usr/lib/tasksel/ and /usr/share/tasksel/. So the isenkram-cli package place two files for tasksel to find. First there is the task description file (/usr/share/tasksel/descs/isenkram.desc):

Task: isenkram-packages
Section: hardware
Description: Hardware specific packages (autodetected by isenkram)
 Based on the detected hardware various hardware specific packages are
Test-new-install: show show
Relevance: 8
Packages: for-current-hardware

Task: isenkram-firmware
Section: hardware
Description: Hardware specific firmware packages (autodetected by isenkram)
 Based on the detected hardware various hardware specific firmware
 packages are proposed.
Test-new-install: mark show
Relevance: 8
Packages: for-current-hardware-firmware

The key parts are Test-new-install which indicate how the task should be handled and the Packages line referencing to a script in /usr/lib/tasksel/packages/. The scripts use other scripts to get a list of packages to install. The for-current-hardware-firmware script look like this to list relevant firmware for the machine:

export PATH
isenkram-autoinstall-firmware -l

With those two pieces in place, the firmware is installed by tasksel during the normal d-i run. :)

If you want to test what tasksel will install when isenkram-cli is installed, run DEBIAN_PRIORITY=critical tasksel --test --new-install to get the list of packages that tasksel would install.

Debian Edu will be pilots in testing this feature, as isenkram is used there now to install firmware, replacing the earlier scripts.

Tags: debian, english, isenkram, sysadmin.

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