bootable systemd-nspawn containers with Alpine Linux

alpine.sh

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

MIRROR=http://dl-cdn.alpinelinux.org/alpine
VERSION=${VERSION:-v3.17}
APKTOOLS_VERSION=2.12.10-r1


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

if [ -z "$1" ]; then
	echo "Usage: $0 <destination>" >&2
	exit 0
fi

dest="$1"
apkdir=$(mktemp -d)
guestarch=aarch64
[ "$(uname -m)" == aarch64 ] && guestarch=aarch64
trap 'rm -r $apkdir' EXIT

wget -qO- $MIRROR/latest-stable/main/aarch64/apk-tools-static-$APKTOOLS_VERSION.apk \
	| tar -xz -C $apkdir || \
	{ echo "Couldn't download apk-tools, the version might have changed..."; 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}
printf '%s/%s/main\n' $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 container was created successfully."