#!/bin/bash
# Filename:      ${GRML_FAI_CONFIG}/hooks/instsoft.ZFS
# Purpose:       Build zfs modules in the chroot, then get rid of packages installed for this alone
# Authors:       (c) András Korn <korn-grml@elan.rulez.org>
# Bug-Reports:   see http://grml.org/bugs/
# License:       This file is licensed under the GPL v2, or, at your option, any later version.
################################################################################

set -u
set -e

# We don't want to install build-essential, dkms et al via package_config
# because they will end up bloating the iso; it seems cleaner to install
# them, build the zfs modules, then remove them.
#
# TODO: if https://bugs.debian.org/cgi-bin/bugreport.cgi?bug=1009179 is ever
# fixed, switch to building a zfs-modules deb and including that.
#
# TODO: convert this into a framework for other classes to ship dkms
# modules: have a hook/script that installs the build-related packages,
# another that builds whatever must be built, and a third that does the cleanup.
#
# TODO: support other architectures grml and grml-live supports (PRs
# welcome, I'm sure).

echo "$0: Installing latest kernel and its headers, as well as build-essential."
# For some reason, apt's autoremove function doesn't pick up some of the
# extra packages we install here, e.g. gcc-11, so work around that by
# keeping track of what gets installed. This is an ugly hack and should not
# be needed, but without it the resulting ISO is hundreds of megabytes
# larger. I hope this kludge can go away eventually.
extra_packages=($($ROOTCMD apt-get --assume-no --download-only --mark-auto -u install \
	build-essential linux-image-amd64 linux-headers-amd64 \
	| sed '0,/The following NEW packages will be installed/d;/^[^ ]/,$d'))
$ROOTCMD apt-get --yes --mark-auto -u install build-essential linux-image-amd64 linux-headers-amd64

# Remove all but the latest kernel (TODO: support passing in the desired
# kernel version by configuration variable instead of using the latest):
echo "$0: Removing all kernel packages except the latest one, if any."
for kernelversion in $($ROOTCMD sh -c 'cd /boot; ls -rt vmlinuz-*' | sed 's/^vmlinuz-//;$d'); do
	echo "$0: Removing obsolete kernel version $kernelversion"
	$ROOTCMD apt-get --yes --purge remove "linux-.*$kernelversion.*"
done

# Earlier Debian releases have a dwarves package; newer ones have pahole.
# This can be needed to build the zfs modules, perhaps depending on kernel
# configuration (TODO: look into this).
echo "$0: Installing pahole or dwarves, whichever is available."
if $ROOTCMD apt-get --yes --mark-auto -u install pahole; then
	pahole=pahole
else
	$ROOTCMD apt-get --mark-auto --yes -u install dwarves
	pahole=dwarves
fi

echo "$0: Installing zfs-dkms itself."
extra_packages=(${extra_packages[@]} $($ROOTCMD apt-get --assume-no --download-only --mark-auto -u install zfs-dkms | sed '0,/The following NEW packages will be installed/d;/^[^ ]/,$d'))
$ROOTCMD apt-get --yes --mark-auto -u install zfs-dkms

# Now invoke the dkms kernel postinst script for the only kernel that's left
# -- normally the zfs-dkms postinst script should do this, but maybe it
# didn't, and redoing it is almost free:
kernelversion=$($ROOTCMD sh -c 'ls -1 /boot/vmlinuz-*' | sed 's@.*boot/vmlinuz-@@')
echo "$0: Building zfs-dkms modules for kernel $kernelversion."
$ROOTCMD /etc/kernel/postinst.d/dkms "$kernelversion"

tempfile=$(mktemp)
echo "$0: Saving built modules into a backup file (removing the dkms package will remove them, but we'll put them back)."
$ROOTCMD tar cf - /lib/modules/$kernelversion/updates/dkms >$tempfile

echo "$0: Removing packages only needed to build zfs modules."
remove_packages=($(echo "${extra_packages[@]}" zfs-dkms '^linux-headers-.*' build-essential $pahole | tr ' ' '\n' | sort -u))
$ROOTCMD apt-get --yes --purge --autoremove remove ${remove_packages[@]}
echo "$0: Trying extra hard to get rid of auto-installed packages. This is a hack that is one of the ways we're trying to work around a perceived bug in apt autoremove and should be a no-op."
$ROOTCMD apt-get --yes --purge autoremove

echo "$0: Restoring backed-up kernel modules."
$ROOTCMD tar xf - <$tempfile
rm $tempfile
$ROOTCMD depmod -a $kernelversion
echo "$0: Completed successfully. Enjoy your zfs."