Hi Gottfried, yes, making a backup is good.
You will want to backup the Guix configuration files and your data. So probably this means you should copy /etc/config.scm and the files in your home directory. You could plug in an ext4-formatted external disk and copy the files with the “cp -a” command. Or learn to use a complicated backup tool like borg, which other pages on the web explain better than I can. However, note that installing Guix on the same disk as another operating system will only be easy if you are using grub-efi-bootloader and if your computer has an OS selection tool built in or if you have installed something like rEFInd. Regards, Florian
