Does this background work for you? I'm trying this on the daily trixie netinst and the installer gets stuck on 'Detect and mount installation media'.
Inspecting the process list; the preseed/early_command does not seem to background the script or process. I've tried the snippet inline and in a script that backgrounds itself (loop), and even that the preseed has an '&' but always the same result. I'm having a similar issue where apt-setup wants to access a local key that is on the cdrom, but I have yet to find a way to copy it onto the the target for apt-setup to pick it up (late_command is too late since apt-setup will have failed by then). Use case: I want to use the CD repository to be able to install and to be used by pbuilder. For the latter, I have self-signed the image Release files; but by doing that, I'm running into apt-setup that uses the keys on the /target and that key is not there yet. So either I get pbuilder to work with the singed repository, or I get the iso installer to work with the unsigned repository. -- g. Marc GPG: 827C FD74 BA46 8152 A041 F3A0 7A6A 4F17 5995 A65B