Add mkosi.precompress

[ragazenta]

I want to create Hybrid MBR disk image, currently I use CompressOutput=no and mkosi.postoutput for this. It would be nice if users could do something to the disk image before being compressed.

#!/bin/bash

set -e

disk_image="${OUTPUTDIR}/${IMAGE_ID}_${IMAGE_VERSION}.raw"

gdisk "$disk_image" > /dev/null <<EOF
r
h
1
n
c
n
n
w
y
EOF

xz --force --check=crc32 --threads=0 --stdout "$disk_image" > "$disk_image.xz"

[DaanDeMeyer]

I think we should implement MBR support in systemd-repart instead of adding precompress scripts to support this use case.

[bluca]

What's the use case for MBR? Don't we want to focus on modern formats like GPT?

[ragazenta]

Older Raspberry Pi models, Pi Zero, Pi 3, the bootloader only support MBR partitioned disk. As a workaround, GPT disk can be made as Hybrid MBR.

[bluca]

Aren't there new models being sold by now which are fully UEFI?

[septatrix]

Aren't there new models being sold by now which are fully UEFI?

For UEFI I think one has to install uboot (which e.g. Fedora does) but they definitely support GPT

PS: There is also https://github.com/pftf/RPi4 though I have not used it yet