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Debian Bullseye netinst iso for serial

For some reason, Debian seems to refuse to ship an netinst ISO image that can do serial output. This seems to have been causing people problems since 2005, at least. To its credit, the Debian Installer will work out whether it’s running on serial and install the correct kernel cmdline for you in grub. Even though the media won’t boot on serial…

Anyway, we needed to install on a PCEngines APU1 which has a respectable 1GHz AMD Bobcat (AMD64) dual-core CPU running at 9W, 2GB of RAM, and three gigabit ports with a wifi card add-on. Totally fine for appliance work at a nice power budget even though it’s an older machine. For some reason there are lots of blogs out there saying to edit the files on the ISO9660 (which you can’t do) and to hit tab on ISOLINUX to get a boot loader (no, that doesn’t work – that’s grub). Very odd. The “right” answer is to unpack a current netinst, edit all the files for providing serial support, and re-pack it. We used lots of blogs’ “suggestions” and experimentation to find a set that works on Bullseye and the APU.

We’re putting our files up for those who need similar serial support or want to continue the work. Debian should get a patch that works on both VGA and serial devices. This will even help the cloud folks who are deploying to QEMU with no video buffer overhead. Be sure to verify the checksums and signature and apply all updates as soon as you install.