debirf

The goal of this project is to create a ​RIP-style kernel and initramfs that leaves the user in a functional debian system.

creating root:

$ mkdir -p debirf/root
$ cd debirf
$ /usr/sbin/debootstrap --exclude=aptitude etch ./root http://ftp.debian.org/debian
$ cd root
$ chroot .
chroot$ echo debirf > /etc/hostname
chroot$ apt-get update
chroot$ echo 'do_initrd = Yes' >> /etc/kernel-img.conf
(modify /etc/kernel-img.conf to not do symlinks?)
chroot$ apt-get install linux-image-2.6-486

* should be able to remove locales
$ find /usr/share/locale -maxdepth 1 -mindepth 1 -type d ! -iname 'en*' -exec rm -rf '{}' \;

chroot$ apt-cache clean
chroot$ rm /var/cache/apt/*.bin
chroot$ rm -rf /var/lib/apt/lists/*
chroot$ mkdir /var/lib/apt/lists/partial
chroot$ exit

extract kernel and initramfs:

mv boot/vmlinuz-* ../
mv boot/initrd.img-* ../

stupid simple method

clean etc/mtab

> etc/mtab

edit etc/fstab:

proc /proc proc defaults 0 0
dev /dev tmpfs size=10M,mode=0755 0 0 #necessary?

link sbin/init to init:

ln -s sbin/init init

archive/gzip filesystem:

find * | cpio -H newc --create  | gzip > ../debirf.cgz

...not quite working. get mount errors about /dev...

tweaked initramfs method

add debirf script to scripts/debirf (either directly or through mkinitramfs):

# debirf.top
cat scripts/debirf <<EOF
mountroot() {
 rootmnt="/"
}

make bin/run-init:

#!/bin/sh
if [ "$1" != "/" ] ; then
  exec /usr/lib/klibc/bin/run-init "$@"
else
  MOUNT_POINT="$1"
  INIT="$2"
  shift 2
  exec "$INIT" "$@"
fi

chmod a+x bin/run-init

archive/gzip filesystem and append to initramfs:

mv ../{initrd-img-*,debirf.cgz}
find * | cpio -H newc --create  | gzip >> ../debirf.cgz

give the following boot parameter:

boot=debirf

things to do:

• debirf/bootlogs
• debirf/commands

potentially useful commands:

dpkg-query -W --showformat='${Priority}: ${Package}\n' | grep ^required

notes

at the moment, our naive approach is failing with

No filesystem could mount root, tried:  ext2 cramfs
Kernel panic - not syncing: VFS: Unable to mount root fs on unknown-block(1,0)

and the main difference between debirf and RIP is that RIP says

Overmounted tmpfs 

just before

Freeing initrd memory

This seems to be from a ​kernel patch that Kent Robotti is using. Can we get this to work without patching the kernel? Can we avoid the attempted mount?

the kernel patch is not sufficient. I tried patching the stock debian kernel so that it "overmounted tmpfs", and the boot still fails with the same error message.

We're booting with the same kernel parameters, so what does the RIP kernel do that the stock debian one does not at boot time? Could we stuff the filesystem we want into a standard debian initramfs instead and loopmount it or something?

mkinitramfs -o ../debirf.cgz -r root
zcat /special-boot/debirf/debirf.cgz | cpio --quiet --extract