Remaster your Own Knoppix

When you copy Knoppix to a new USB flash disk using flash-knoppix, it is possible to include personal settings, additional programs, and configuration changes (Figure 3). All changes are compressed to a new overlay image inside the destination's KNOPPIX folder, thus minimizing the required space.

Figure 3: Remastering a custom Knoppix.

A teacher could, for example, install documents and exercises and make a new version containing these changes for the students. It's still easy to reset the modified Knoppix version to the original state by simply deleting the additional overlay file.

The code necessary for creating a new overlay on-the-fly from the running Knoppix system, excluding some unwanted files and cloop-compressing the image to the destination file, is shown in Listing 2.

I'm somewhat surprised that the code in Listing 2 really worked right away. Apparently, it's sufficient to ignore temporary files and sockets in order to create the ISO filesystem stream for compression, and the cloop tool create_compressed_fs will pad missing data with zeros in order to always write full blocks.

UEFI Secure Boot Support

Knoppix has been coming with a signed UEFI secure bootloader for a while now, but this does not mean it will boot right away on computers with UEFI Secure Boot enabled in the firmware. On first boot with UEFI, a blue screen will be displayed (Figure 4), telling the user to enroll the file loader.efi into the secure boot configuration. This is not an error message, though it might look like one; don't give up yet!

Figure 4: Don't be discouraged by the blue screen: configuring a UEFI boot requires an extra step.

Just follow the instructions, which I describe in more detail online [5] . After this "enrollment" has been successfully conducted (it's only needed once to allow booting the Linux loader permanently), Knoppix will display its UEFI boot screen (without the usual penguin logo), and, in most cases, will continue to start up normally. In some cases, the boot procedure will be silent, because of missing text screen support in UEFI, until the graphical interface starts up.

Conclusion

Knoppix 8.1 is the latest update of the Debian-based Knoppix live distribution, which now comes as a single image for DVD and direct USB flash disk installation. For more information about the new release, see the Knoppix website.

init=/bin/bash

init=/bin/vim

The Author

Klaus Knopper is an engineer, creator of Knoppix, and cofounder of LinuxTag expo. He works as a regular professor at the University of Applied Sciences, Kaiserslautern, Germany.