Create bootable systemd-nspawn containers with Alpine, Arch Linux or Ubuntu

alpine-container.sh

#!/bin/bash -e
# Creates a systemd-nspawn container with Alpine

MIRROR=http://dl-cdn.alpinelinux.org/alpine
VERSION=${VERSION:-v3.20}
APKTOOLS_VERSION=2.14.4-r1


wget_or_curl () {
	if command -v wget >/dev/null; then
		wget -qO- "$1"
	elif command -v curl >/dev/null; then
		curl -Ls "$1"
	else
		echo "missing either curl or wget" >&2
		return 1
	fi
}

if [ $UID -ne 0 ]; then
	echo "run this script as root" >&2
	exit 1
fi

dest="$1"
if [ -z "$dest" ]; then
	echo "Usage: $0 <destination>" >&2
	exit 0
fi
if [ -e "$dest/usr/bin" ]; then
	echo "destination already seems to contain a root file system" >&2
	exit 1
fi

if [[ "$(uname -m)" =~ ^i[3456]86|x86 ]]; then
	toolarch=x86
	guestarch=$toolarch
	[ "$(uname -m)" = x86_64 ] && guestarch=x86_64
elif [[ "$(uname -m)" =~ ^arm|aarch64 ]]; then
	toolarch=armv7
	guestarch=$toolarch
	[ "$(uname -m)" = aarch64 ] && guestarch=aarch64
else
	echo "unsupported architecture" >&2
	exit 1
fi
apkdir=$(mktemp -d)
trap 'rm -rf $apkdir' EXIT

wget_or_curl "$MIRROR/latest-stable/main/$toolarch/apk-tools-static-$APKTOOLS_VERSION.apk" \
	| tar -xz -C $apkdir || \
	{ echo "couldn't download apk-tools, the version might have changed..." >&2; exit 1; }

$apkdir/sbin/apk.static \
	-X $MIRROR/$VERSION/main -U --arch $guestarch \
	--allow-untrusted --root "$dest" \
	--initdb add alpine-base

mkdir -p "$dest"/{etc/apk,root}
# configure mirror
printf '%s/%s/main\n%s/%s/community\n' "$MIRROR" $VERSION "$MIRROR" $VERSION >"$dest"/etc/apk/repositories
for i in $(seq 0 10); do # https://github.com/systemd/systemd/issues/852
	echo "pts/$i" >>"$dest/etc/securetty"
done
# make console work
sed '/tty[0-9]:/ s/^/#/' -i "$dest"/etc/inittab
printf 'console::respawn:/sbin/getty 38400 console\n' >>"$dest"/etc/inittab
# minimal boot services
for s in hostname bootmisc syslog; do
	ln -s /etc/init.d/$s "$dest"/etc/runlevels/boot/$s
done
for s in killprocs savecache; do
	ln -s /etc/init.d/$s "$dest"/etc/runlevels/shutdown/$s
done


echo ""
echo "Alpine $VERSION $guestarch container was created successfully."

arch-container.sh

#!/bin/bash -e
# Creates a systemd-nspawn container with Arch Linux

MIRROR=http://mirror.fra10.de.leaseweb.net/archlinux
ISO_DATE=latest
PKG_GROUPS="base"


wget_or_curl () {
	if command -v wget >/dev/null; then
		wget "$1" -O "$2"
	elif command -v curl >/dev/null; then
		curl -L "$1" -o "$2"
	else
		echo "missing either curl or wget" >&2
		return 1
	fi
}

if [ $UID -ne 0 ]; then
	echo "run this script as root" >&2
	exit 1
fi

dest="$1"
if [ -z "$dest" ]; then
	echo "Usage: $0 <destination>" >&2
	exit 0
fi
if [ -e "$dest/usr/bin" ]; then
	echo "destination already seems to contain a root file system" >&2
	exit 1
fi

[ "$(uname -m)" = x86_64 ] || { echo "unsupported architecture" >&2; exit 1; }
tarfile=$(mktemp)
trap 'rm $tarfile' EXIT

wget_or_curl "$MIRROR/iso/$ISO_DATE/archlinux-bootstrap-x86_64.tar.zst" $tarfile

mkdir -p "$dest"
tar -xaf $tarfile -C "$dest" --strip-components=1 --numeric-owner

# configure mirror
printf 'Server = %s/$repo/os/$arch\n' "$MIRROR" >"$dest"/etc/pacman.d/mirrorlist
sed '/^root:/ s|\*||' -i "$dest/etc/shadow" # passwordless login
rm "$dest/etc/resolv.conf" # systemd configures this
# https://github.com/systemd/systemd/issues/852
[ -f "$dest/etc/securetty" ] && \
	printf 'pts/%d\n' $(seq 0 10) >>"$dest/etc/securetty"
# seems to be this bug https://github.com/systemd/systemd/issues/3611
systemd-machine-id-setup --root="$dest"
# install the packages
systemd-nspawn -q -D "$dest" sh -c "
pacman-key --init && pacman-key --populate
pacman -Sy --noconfirm --needed ${PKG_GROUPS}
"


echo ""
echo "Arch Linux container was created successfully (bootstrapped from $ISO_DATE)"

ubuntu-container.sh

#!/bin/bash -e
# Creates a systemd-nspawn container with Ubuntu

CODENAME=${CODENAME:-noble}

wget_or_curl () {
	if command -v wget >/dev/null; then
		wget "$1" -O "$2"
	elif command -v curl >/dev/null; then
		curl -L "$1" -o "$2"
	else
		echo "missing either curl or wget" >&2
		return 1
	fi
}

if [ $UID -ne 0 ]; then
	echo "run this script as root" >&2
	exit 1
fi

dest="$1"
if [ -z "$dest" ]; then
	echo "Usage: $0 <destination>" >&2
	exit 0
fi
if [ -e "$dest/usr/bin" ]; then
	echo "destination already seems to contain a root file system" >&2
	exit 1
fi

if [ "$(uname -m)" = x86_64 ]; then
	guestarch=amd64
elif [ "$(uname -m)" = aarch64 ]; then
	guestarch=arm64
else
	echo "unsupported architecture" >&2
	exit 1
fi
rootfs=$(mktemp)
trap 'rm $rootfs' EXIT

wget_or_curl "http://cloud-images.ubuntu.com/${CODENAME}/current/${CODENAME}-server-cloudimg-${guestarch}-root.tar.xz" $rootfs

mkdir -p "$dest"
tar -xaf $rootfs -C "$dest" --numeric-owner

sed '/^root:/ s|\*||' -i "$dest/etc/shadow" # passwordless login
rm "$dest/etc/resolv.conf" # systemd configures this
# https://github.com/systemd/systemd/issues/852
[ -f "$dest/etc/securetty" ] && \
	printf 'pts/%d\n' $(seq 0 10) >>"$dest/etc/securetty"
# container needs no mounts
>"$dest/etc/fstab"
# disable services and uninstall packages
systemd-nspawn -q -D "$dest" sh -c '
[ -s /etc/environment ] && . /etc/environment
for unit in ssh.service ssh.socket systemd-timesyncd systemd-networkd-wait-online systemd-resolved; do
    systemctl is-enabled "$unit" && systemctl disable "$unit"
done
apt-get -qq satisfy -y --purge "Conflicts: lxcfs, lxd, snapd, cloud-init" || \
apt-get -qq purge --autoremove snapd lxcfs lxd cloud-init
'


echo ""
echo "Ubuntu $CODENAME $guestarch container was created successfully"

Awesome, thank you for sharing the script.
It's a little bit ugly but I change to use edge instead.

VERSION=edge
APKTOOLS_VERSION=$(curl -s $MIRROR/edge/main/$ARCH/ | awk -F'=' 'match($0, /href="apk-tools-static-(.*).apk">/, a) {print a[1]}')

Thank you, very useful scripts, saved a lot of time.

My fork of your script is here: https://github.com/mikhailnov/rootfs-scripts/blob/master/rootfs-ubuntu.sh

Starting alpine image on Ubuntu 20 gives

Sep 07 02:53:14 Gelato systemd-nspawn[79402]: getty: console: TIOCSCTTY: Operation not permitted
Sep 07 02:53:24 Gelato systemd-nspawn[79402]: getty: console: TIOCSCTTY: Operation not permitted
Sep 07 02:53:34 Gelato systemd-nspawn[79402]: getty: console: TIOCSCTTY: Operation not permitted
Sep 07 02:53:44 Gelato systemd-nspawn[79402]: getty: console: TIOCSCTTY: Operation not permitted
Sep 07 02:53:54 Gelato systemd-nspawn[79402]: getty: console: TIOCSCTTY: Operation not permitted

but

systemd-nspawn -M alpine -- /sbin/getty -nl /bin/ash 0 /dev/console

works.

printf 'console::respawn:/sbin/getty 38400 console\n' >>"$dest"/etc/inittab

does not seem to work.

Thank you so much for this! I hope you don't mind me using bits of your scripts here: https://github.com/X0RW3LL/XenSpawn
Linked to this gist in the references section <3

Thanks for this script! Building my own based on yours :)

Thanks for this script! Building my own based on yours :)

heh ;)