#!/bin/sh
# Copyright 2022 Helmut Grohne <helmut@subdivi.de>
# SPDX-License-Identifier: MIT

# shellcheck disable=SC2016 # Intentional quoting technique

: <<'POD2MAN'
=head1 NAME

debvm-create - Create a VM image for various Debian releases and architectures

=head1 SYNOPSIS

B<debvm-create> [B<-a> I<architecture>] [B<-h> I<hostname>] [B<-k> F<sshkey>] [B<-m> I<mirror>] [B<-o> F<output>] [B<-p> I<package>] [B<-r> I<release>] [B<-z> I<size_in_GB>] [B<--> I<mmdebstrap options>]

=head1 DESCRIPTION

B<debvm-create> is essentially a thin wrapper around B<mmdebstrap> for creating a raw ext4 filesystem image for booting with B<debvm-run>.
The purpose of these images primarily is testing the different releases and architectures without access to a physical machine of that architecture.
Beyond essential packages, the image will contain B<apt>, an init system and a suitable kernel package.
Notably absent is a bootloader and a partition table.
In order to boot such an image, one is supposed to extract the kernel and initrd from the image and pass it to a suitable bootloader.
No user account is created and root can login without specifying a password.

=head1 OPTIONS

=over 8

=item B<-a> I<architecture>, B<--architecture>=I<architecture>

Specify a Debian architecture name.
By default, the native architecture is being used.
A suitable kernel image is automatically selected and installed into the image.

=item B<-h> I<hostname>, B<--hostname>=I<hostname>

Set the hostname of the virtual machine.
By default, the hostname is B<testvm>.

=item B<-k> F<sshkey>, B<--sshkey>=F<sshkey>

Install the given ssh public key file into the virtual machine image for the root user.
This option also causes the ssh server to be installed.
By default, no key or server is installed.
To connect to the vm, pass a port number to B<debvm-run> with the B<-s> option.

=item B<-m> I<mirror>, B<--mirror>=I<mirror>

Specify the Debian mirror to be used for downloading packages and to be configured inside the virtual machine image.
By default, L<http://deb.debian.org/debian> is being used.

=item B<-o> F<output>, B<--output>=F<output>

Specify the file name of the resulting virtual machine image.
By default, it is written to F<rootfs.ext4>.

=item B<-p> I<package>, B<--package>=I<package>

Request additional packages to be installed into the virtual machine image.
This option can be specified multiple times and packages can be separated by a comma.
Package recommendations are not honoured.
If a linux-image is passed here, it will replace the one selected by default.

=item B<-r> I<release>, B<--release>=I<release>

Use the given Debian release.
By default, B<unstable> is being used.

=item B<-z> I<size_in_GB>, B<--size>=I<size_in_GB>

Specify the minimum image size in giga bytes.
The resulting image will be grown as a sparse file to this size if necessary.
The default is 1 GB.

=item B<--> I<mmdebstrap options>

All options beyond a double dash are passed to B<mmdebstrap> before the suite, target and mirror specification.
This can be used to provide additional hooks for image customization.

=back

=head1 SEE ALSO

    debvm-run(1) mmdebstrap(1)

=cut
POD2MAN

set -u

ARCHITECTURE=$(dpkg --print-architecture)
IMAGE=rootfs.ext4
INCLUDE_PACKAGES=init
MIRROR="http://deb.debian.org/debian"
SIZE=$((1024*1024*1024))
SSHKEY=
SUITE=unstable
VMNAME=testvm

SHARE_DIR="${0%/*}/../share"

nth_arg() {
	shift "$1"
	printf "%s" "$1"
}

die() {
	echo "$*" 1>&2
	exit 1
}
usage() {
	die "usage: $0 [-a architecture] [-h hostname] [-k sshkey] [-m mirror] [-o output] [-p packages] [-r release] [-z size_in_GB] [-- mmdebstrap options]"
}
usage_error() {
	echo "error: $*" 1>&2
	usage
}

opt_architecture() {
	ARCHITECTURE=$1
}
opt_hostname() {
	VMNAME=$1
}
opt_mirror() {
	MIRROR=$1
}
opt_sshkey() {
	SSHKEY=$1
}
opt_output() {
	IMAGE=$1
}
opt_package() {
	INCLUDE_PACKAGES="$INCLUDE_PACKAGES,$1"
}
opt_release() {
	SUITE=$1
}
opt_size() {
	SIZE=$(($1*1024*1024*1024))
}

while getopts :a:h:k:m:o:p:r:z:-: OPTCHAR; do
	case "$OPTCHAR" in
		a)	opt_architecture "$OPTARG"	;;
		h)	opt_hostname "$OPTARG"		;;
		k)	opt_sshkey "$OPTARG"		;;
		m)	opt_mirror "$OPTARG"		;;
		o)	opt_output "$OPTARG"		;;
		p)	opt_package "$OPTARG"		;;
		r)	opt_release "$OPTARG"		;;
		z)	opt_size "$OPTARG"		;;
		-)
			case "$OPTARG" in
				help)
					usage
				;;
				architecture|hostname|mirror|output|package|release|size|sshkey)
					test "$OPTIND" -gt "$#" && usage_error "missing argument for --$OPTARG"
					"opt_$OPTARG" "$(nth_arg "$OPTIND" "$@")"
					OPTIND=$((OPTIND+1))
				;;
				architecture=*|hostname=*|mirror=*|output=*|package=*|release=*|size=*|sshkey=*)
					"opt_${OPTARG%%=*}" "${OPTARG#*=}"
				;;
				*)
					usage_error "unrecognized option --$OPTARG"
				;;
			esac
		;;
		:)
			usage_error "missing argument for -$OPTARG"
		;;
		'?')
			usage_error "unrecognized option -$OPTARG"
		;;
		*)
			die "internal error while parsing command options, please report a bug"
		;;
	esac
done
shift "$((OPTIND - 1))"

if test -n "$SSHKEY" && ! test -f "$SSHKEY"; then
	die "error: ssh keyfile '$SSHKEY' not found"
fi

case "$SUITE" in
	jessie)
		DEBVER=8
	;;
	stretch)
		DEBVER=9
	;;
	buster)
		DEBVER=10
	;;
	bullseye|stable)
		DEBVER=11
	;;
	bookworm|testing)
		DEBVER=12
	;;
	trixie)
		DEBVER=13
	;;
	forky)
		DEBVER=14
	;;
	sid|unstable)
		DEBVER=999
	;;
	*)
		die "unrecognized Debian release: $SUITE"
	;;
esac

KERNEL_SUFFIX=-$ARCHITECTURE
case "$ARCHITECTURE" in
	amd64|arm64)
		KERNEL_SUFFIX="-cloud-$ARCHITECTURE"
		if test "$DEBVER" -le 9; then
			KERNEL_SUFFIX="-$ARCHITECTURE"
		fi
	;;
	armhf)
		KERNEL_SUFFIX=-armmp
	;;
	i386)
		KERNEL_SUFFIX=-686-pae
	;;
	mips64el)
		KERNEL_SUFFIX=-5kc-malta
	;;
	mipsel)
		KERNEL_SUFFIX=-4kc-malta
	;;
	ppc64el)
		KERNEL_SUFFIX=-powerpc64le
	;;
esac

case ",$INCLUDE_PACKAGES," in
	*,linux-image-*)
	;;
	*)
		INCLUDE_PACKAGES="$INCLUDE_PACKAGES,linux-image$KERNEL_SUFFIX"
	;;
esac

if test -n "$SSHKEY"; then
	INCLUDE_PACKAGES="$INCLUDE_PACKAGES,openssh-server"
fi

# add a DNS resolver
INCLUDE_PACKAGES="$INCLUDE_PACKAGES,?exact-name(libnss-resolve)"
set -- "--customize-hook=$SHARE_DIR/customize-resolved.sh" "$@"

# construct mmdebstrap options as $@:
set -- \
	--verbose \
	--variant=apt \
	--format=ext2 \
	"--architecture=$ARCHITECTURE" \
	"--include=$INCLUDE_PACKAGES" \
	'--customize-hook=echo "LABEL=debvm / ext4 defaults 0 1" >"$1/etc/fstab"' \
	"$@"


# set up a hostname
set -- \
	"--customize-hook=echo $VMNAME >"'"$1/etc/hostname"' \
	"--customize-hook=echo 127.0.0.1 localhost $VMNAME >"'"$1/etc/hosts"' \
	"$@"

# allow password-less root login
set -- '--customize-hook=chroot "$1" passwd --delete root' "$@"

# dhcp on all network interfaces
set -- "--customize-hook=$SHARE_DIR/customize-networkd.sh" "$@"

# add ssh key for root
if test -n "$SSHKEY"; then
	set -- \
		'--customize-hook=mkdir -m700 -p "$1/root/.ssh"' \
		"--customize-hook=upload $SSHKEY /root/.ssh/authorized_keys" \
		"$@"
fi

set -- --skip=cleanup/apt/lists "$@"
set -- "--customize-hook=$SHARE_DIR/customize-dpkgavailable.sh" "$@"

if test "$DEBVER" -le 8; then
	# Use obsolete and expired keys.
	set -- '--keyring=/usr/share/keyrings/debian-archive-removed-keys.gpg' "$@"
	set -- --aptopt='Apt::Key::gpgvcommand "/usr/libexec/mmdebstrap/gpgvnoexpkeysig"' "$@"
	set -- --hook-dir=/usr/share/mmdebstrap/hooks/jessie-or-older "$@"
fi

if test "$DEBVER" -ge 12; then
	# Avoid the usrmerge package
	set -- --hook-dir=/usr/share/mmdebstrap/hooks/merged-usr "$@"
fi

set -- "--customize-hook=$SHARE_DIR/customize-autologin.sh" "$@"

# suite target mirror
set -- "$@" "$SUITE" "$IMAGE" "deb $MIRROR $SUITE main"

set -ex

mmdebstrap "$@"

IMAGESIZE=$(stat -c %s "$IMAGE")
if test "$IMAGESIZE" -lt "$SIZE"; then
	truncate -s "$SIZE" "$IMAGE"
	/sbin/resize2fs "$IMAGE"
fi
/sbin/tune2fs -L debvm -i 0 -O extents,uninit_bg,dir_index,has_journal "$IMAGE"
# Must fsck after tune2fs: https://ext4.wiki.kernel.org/index.php/UpgradeToExt4
/sbin/fsck.ext4 -fDp "$IMAGE"