Re: hard disk installation method fails

[Charles Curley <charlescurley@charlescurley.com>]

On Sat, 18 Feb 2023 12:05:11 +0800
lsg <loushanguan2015@sina.com> wrote:

> Really? i am afraid vmlinuz and initrd pair in iso file don't include 
> program that search disk for iso file, as pair in hd-media directory
> does
> 
> Debian11.6/main/installer-amd64/current/images/hd-media
> 
> though it's possible to boot iso file with grub, but it's too
> complicated
> 
> it seems few users are using hard disk installation method theses days

I haven't been entirely clear about what I do. I do boot d-i using
grub. The following should make it a bit less opaque.

root@dti386:~# cat /etc/grub.d/50_netinst 
#!/bin/sh
exec tail -n +3 $0
# This file provides an easy way to add custom menu entries.  Simply type the
# menu entries you want to add after this comment.  Be careful not to change
# the 'exec tail' line above.
menuentry "Install Debian 12 OS (preseeded)" {
    set root='hd0,msdos5'
    set isofile=/firmware-testing-i386-netinst.iso
    insmod part_msdos
    insmod loopback
    loopback loop (hd0,msdos5)$isofile
    linux (loop)/install.386/vmlinuz auto=true file=/media/preseed.cfg
    initrd (loop)/install.386/initrd.gz
}
menuentry "Install Debian 12 OS (Expert)" {
    set root='hd0,msdos5'
    set isofile=/firmware-testing-i386-netinst.iso
    insmod part_msdos
    insmod loopback
    loopback loop (hd0,msdos5)$isofile
    linux (loop)/install.386/vmlinuz rescue/enable=true
    initrd (loop)/install.386/initrd.gz
}
root@dti386:~# 

The key is the loopback module: grub mounts the iso file as a loopback
device, pulls what it needs from the iso file, and goes from there.
Using the loopback facility eliminates the necessity of a separate
initrd and kernel.

The iso file is on /dev/[vs]da5, the first extended partition, with a
FAT file system. The idea is that the main partitions could get badly
mangled, but grub and this partition survive. This gives you a rescue
or re-installation capability without CD-ROMs, USB sticks, etc.

And, yes, these use Testing/Bookworm's weekly build, not Bullseye's.
The same principle applies to Bullseye.

-- 
Does anybody read signatures any more?

https://charlescurley.com
https://charlescurley.com/blog/