My plan was to create the img of the disk, and use mkisofs to create a bootable linux CD from it. However I'm stuck between 'how to turn installation into file you can make an iso' part.

Create a bootable USB stick from Linux I was keeping the best for last. If you are running Linux, you can use the dd command (as in the instructions for macOS above) to create the bootable drive.

Perhaps they referenced this guide to create a bootable Live USB on Windows, allowing them to test drive something like Ubuntu without making any changes to their PC.

Creating your bootable Linux USB involves several key steps: Download the ISO File: Visit the official website of your chosen Linux distribution and download the ISO file. Prepare the Bootable USB: ...

Thanks to open-source gem UNetbootin, you can quickly and easily transform a flash drive into the ultimate rescue tool.

We've previously featured rather involved guides to putting Linux on a flash drive, but UNetbootin does it all for you, from downloading the right ISO to setting up a USB stick as a bootable Linux ...

After the download, plug in a USB stick (2GB or larger), and select System→Administration→Startup Disk Creator from the Ubuntu menu. Select the downloaded .iso and the target USB device—in the case ...

We usually use Unetbootin to create a bootable thumb drive from a Linux ISO, but it turns out you don't even need a thumb drive if you want to boot the live CD on the same computer that has ...

S2-HyperCalc A minimal 64-bit bootable Linux ISO that runs a custom C program as init. Built using a precompiled Linux kernel, GRUB bootloader, and custom initramfs without a full Linux distro.