kvmstrap

#!/bin/bash

# Version info
# TODO: Manually increase this number after any substantial changes
VERSION=1

set -e

BASE="$(dirname "$0")"
SRC="$BASE/rootfs"
DST=/tmp/target
INPUT="${1:-input.qcow2}"
APT_SOURCE="${APT_SOURCE:-https://mirrors.ustc.edu.cn}"
cd "$BASE"
. ./variables

run() {
  chroot "$DST" "$@"
}

add_file() {
  while [ "$#" -ne 0 ]; do
    rsync -rlp "$SRC/$1" "$DST/$1"
    shift
  done
}

add_package() {
  DEBIAN_FRONTEND=noninteractive run apt-get install -y --no-install-recommends "$@"
}

remove_package() {
  DEBIAN_FRONTEND=noninteractive run apt-get purge -y --autoremove "$@"
}

mount_all() {
  mount -t tmpfs none "$DST/dev"
  chmod 755 "$DST/dev"
  mknod -m0666 "$DST/dev/null" c 1 3
  mknod -m0666 "$DST/dev/random" c 1 8
  mknod -m0666 "$DST/dev/urandom" c 1 9
  mknod -m0666 "$DST/dev/zero" c 1 5
  ln -sf /proc/self/fd/0 "$DST/dev/stdin"
  ln -sf /proc/self/fd/1 "$DST/dev/stdout"
  ln -sf /proc/self/fd/2 "$DST/dev/stderr"
  mkdir -p "$DST/dev/pts"
  mount -t devpts none "$DST/dev/pts"
  mount -t proc proc "$DST/proc"
  mount -t tmpfs none "$DST/run"
  mount -t sysfs sys "$DST/sys"
  mount -t tmpfs none "$DST/tmp"
}

umount_all() {
  umount "$DST/dev/pts"
  umount "$DST/dev"
  umount "$DST/proc"
  umount "$DST/run"
  umount "$DST/sys"
  umount "$DST/tmp"
  umount "$DST"
}

mkdir -p "$DST"
if [ -b "$INPUT" ]; then
  mount "$INPUT" "$DST"
else
  qemu-img resize "$INPUT" 4096M
  guestmount -a "$INPUT" -m /dev/sda1 "$DST"
fi

mount_all
trap umount_all EXIT

# Preliminary cleanup
rm -f "$DST/etc/resolv.conf"
cp -f /etc/resolv.conf "$DST/etc/resolv.conf"
add_file /etc/apt/
run sed -i "s,%APT_SOURCE%,$APT_SOURCE,g" /etc/apt/sources.list.d/ubuntu.sources
run apt-mark auto '~i!~M'
run apt-get update
run apt-get -y dist-upgrade

add_package linux-virtual ubuntu-minimal ubuntu-server ubuntu-standard

# Add files
add_file /etc/{apt,cloud,default,profile.d,skel,ssh,sysctl.d,systemd}/ /etc/locale.gen

# Remove "pass" from fstab
sed -Ei 's/\b[0-9]+$/0/g' "$DST"/etc/fstab

# Remove root password
#sed -Ei 's/^(root:)[^:]*(:.*$)/\1\2/' "$DST"/etc/shadow
run passwd -d root

# Simulate systemctl enable
#ln -sfn /etc/systemd/system/vlab-startup.service "$DST"/etc/systemd/system/multi-user.target.wants/vlab-startup.service
run systemctl enable vlab-startup.service

# Write version info
VLAB_VERSION="$VERSION:$(date +%y%m%d)"
if [ -n "$GITHUB_RUN_NUMBER" ]; then
  VLAB_VERSION="$VLAB_VERSION-gh-$GITHUB_RUN_NUMBER"
fi
FILE="$DST"/etc/vlab_version
echo "VLAB_DISTRO=ubuntu" > "$FILE"
echo "VLAB_VERSION=$VLAB_VERSION" >> "$FILE"
chmod 444 "$FILE"

# Set the apt source of the resulting image to USTC mirrors
add_file /etc/apt/sources.list.d/ubuntu.sources
run sed -i "s,%APT_SOURCE%,https://mirrors.ustc.edu.cn,g" /etc/apt/sources.list.d/ubuntu.sources
run apt clean

# Final cleanup
set +e
rm -rf "$DST/var/lib/apt/lists"/* "$DST/var/lib/dpkg"/*-old
rm -rf "$DST/var/cache"/*
rm -f "$DST/etc/resolv.conf"
ln -sfn ../run/systemd/resolve/stub-resolv.conf "$DST/etc/resolv.conf"
rm -rf "$DST/etc/ssh"/ssh_host_*_key{,.pub}
rmdir "$DST"/*.usr-is-merged || true