Add alpine-make-vm-image script
This commit is contained in:
Jakub Jirutka
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1 changed files with 358 additions and 0 deletions
358
alpine-make-vm-image
Executable file
358
alpine-make-vm-image
Executable file
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#!/bin/sh
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# vim: set ts=4:
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#---help---
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# Usage: alpine-make-vm-image [options] [--] <image> [<script> [<script-opts...>]]
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#
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# This script creates a bootable Alpine Linux disk image for virtual machines.
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# Note that it does not create any partitions (it's really not needed),
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# filesystem is created directly on the image.
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#
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# Arguments:
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# <image> Path of disk image to use or create if not exists.
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#
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# <script> Path of script to execute after installing base system in
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# the mounted image and before umounting it.
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#
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# <script-opts> Arguments to pass to the script.
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#
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# Options and Environment Variables:
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# -f --image-format IMAGE_FORMAT Format of the disk image (see qemu-img --help).
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#
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# -s --image-size IMAGE_SIZE Size of the disk image to create in bytes or with suffix
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# (e.g. 1G, 1024M). Default is 2G.
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#
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# -i --initfs-features INITFS_FEATURES List of additional mkinitfs features (basically modules)
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# to be included in initramfs (see mkinitfs -L). "base" and
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# $ROOTFS is always included, don't specify them here.
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# Default is "scsi virtio".
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#
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# -k --kernel-flavor KERNEL_FLAVOR The kernel flavour to install; vanilla, hardened,
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# or virthardened. Default is virthardened.
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#
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# --keys-dir KEYS_DIR Path of directory with Alpine keys to copy into the image.
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# Default is /etc/apk/keys.
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#
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# -C --no-cleanup (CLEANUP) Don't umount and disconnect image when done.
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#
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# -p --packages PACKAGES Additional packages to install into the image.
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#
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# -r --repositories-file REPOS_FILE Path of repositories file to copy into the image.
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# Default is /etc/apk/repositories.
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#
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# --rootfs ROOTFS Filesystem to create on the image. Default is ext4.
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#
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# -c --script-chroot (SCRIPT_CHROOT) Bind <script>'s directory at /mnt inside image and chroot
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# into the image before executing <script>.
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#
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# -h --help Show this help message and exit.
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#
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# -v --version Print version and exit.
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#
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# Each option can be also provided by environment variable. If both option and
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# variable is specified and the option accepts only one argument, then the
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# option takes precedence.
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#
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# https://github.com/jirutka/alpine-make-vm-image
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#---help---
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set -eu
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readonly APK='apk --no-progress'
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readonly PROGNAME='alpine-make-vm-image'
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readonly VERSION='0.0.0'
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readonly VIRTUAL_PKG=".make-$PROGNAME"
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die() {
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printf '\033[1;31mERROR:\033[0m %s\n' "$@" >&2 # bold red
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exit 1
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}
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einfo() {
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printf '\n\033[1;36m> %s\033[0m\n' "$@" >&2 # bold cyan
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}
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# Prints help and exists with the specified status.
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help() {
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sed -En '/^#---help---/,/^#---help---/p' "$0" | sed -E 's/^# ?//; 1d;$d;'
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exit ${1:-0}
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}
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cleanup() {
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set +u
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trap '' EXIT HUP INT TERM # unset trap to avoid loop
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cd /
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if [ -n "$mount_dir" ]; then
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umount_recursively "$mount_dir" \
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|| die "Failed to unmount $mount_dir; unmount it and disconnect $nbd_dev manually"
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rm -Rf "$mount_dir" || :
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fi
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qemu-nbd --disconnect "$nbd_dev" \
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|| die "Failed to disconnect $nbd_dev; disconnect it manually"
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$APK del $VIRTUAL_PKG
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}
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# Attaches the specified image as a NBD block device and prints its path.
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attach_image() {
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local image="$1"
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local format="${2:-}"
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local nbd_dev
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modprobe nbd max_part=0 || true
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nbd_dev=$(get_available_nbd) \
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|| die "No available nbd device found!"
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qemu-nbd --connect="$nbd_dev" ${format:+--format=$format} "$image" \
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&& echo "$nbd_dev"
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}
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# Prints UUID of filesystem on the specified block device.
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blk_uuid() {
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local dev="$1"
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blkid "$dev" | sed -En 's/.*UUID="([^"]+)".*/\1/p'
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}
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# Prints path of available nbdX device, or returns 1 if not any.
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get_available_nbd() {
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local dev; for dev in /dev/nbd*; do
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if [ "$(blockdev --getsize64 "$dev")" -eq 0 ]; then
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echo "$dev"; return
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fi
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done
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return 1
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}
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# Installs tools in the host system needed for creating the specified filesystem.
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install_fs_tools() {
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local fs="$1" # filesystem name
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# We need load btrfs module early to avoid the error message:
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# 'failed to open /dev/btrfs-control'
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if ! grep -q -w "$fs" /proc/filesystems; then
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modprobe $fs
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fi
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local pkg
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case "$fs" in
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ext4) pkg='e2fsprogs';;
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btrfs) pkg='btrfs-progs';;
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xfs) pkg='xfsprogs';;
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*) die "Unsupported filesystem: $fs";;
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esac
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$APK add -t $VIRTUAL_PKG $pkg
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}
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# Prepares chroot at the specified path.
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prepare_chroot() {
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local dest="$1"
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mkdir -p "$dest"/proc "$dest"/dev "$dest"/sys
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mount -t proc none "$dest"/proc
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mount --bind /dev "$dest"/dev
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mount --bind /sys "$dest"/sys
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install -D -m 644 /etc/resolv.conf "$dest"/etc/resolv.conf
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}
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# Adds specified services to the runlevel. Current working directory must be
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# root of the image.
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rc_add() {
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local runlevel="$1"; shift # runlevel name
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local services="$@" # names of services
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local svc; for svc in $services; do
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mkdir -p etc/runlevels/$runlevel
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ln -s /etc/init.d/$svc etc/runlevels/$runlevel/$svc
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echo " * service $svc added to runlevel $runlevel"
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done
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}
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# Installs and configures extlinux.
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setup_extlinux() {
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local mnt="$1" # path of directory where is root device currently mounted
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local root_dev="$2" # root device
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local modules="${3:-}" # modules which should be loaded before pivot_root
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local default_kernel="${4:-"vanilla"}" # name of default kernel to boot
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local kernel_opts="${5:-}" # default kernel options
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sed -Ei -e "s|^[# ]*(root)=.*|\1=$root_dev|" \
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-e "s|^[# ]*(default_kernel_opts)=.*|\1=\"$kernel_opts\"|" \
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-e "s|^[# ]*(modules)=.*|\1=\"$modules\"|" \
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-e "s|^[# ]*(default)=.*|\1=$default_kernel|" \
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"$mnt"/etc/update-extlinux.conf
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extlinux --install "$mnt"/boot
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chroot "$mnt" update-extlinux --warn-only 2>&1 \
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| grep -Fv 'extlinux: cannot open device /dev' >&2
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}
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# Configures mkinitfs.
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setup_mkinitfs() {
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local mnt="$1" # path of directory where is root device currently mounted
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local features="$2" # list of mkinitfs features
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features=$(printf '%s\n' $features | sort | uniq | xargs)
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sed -Ei "s|^[# ]*(features)=.*|\1=\"$features\"|" \
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"$mnt"/etc/mkinitfs/mkinitfs.conf
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}
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# Unmounts all filesystem under the specified directory tree.
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umount_recursively() {
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local mount_point="$1"
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test -n "$mount_point" || return 1
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cat /proc/mounts \
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| cut -d ' ' -f 2 \
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| grep "^$mount_point" \
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| sort -r \
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| xargs umount -rn
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}
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#============================= M a i n ==============================#
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opts=$(getopt -n $PROGNAME -o cCf:hi:k:p:r:s:v \
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-l image-format:,image-size:,initfs-features:,kernel-flavor:,keys-dir:,no-cleanup,packages:,repositories-file:,rootfs:,script-chroot,help,version \
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-- "$@") || help 1 >&2
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eval set -- "$opts"
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while [ $# -gt 0 ]; do
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n=2
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case "$1" in
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-f | --image-format) IMAGE_FORMAT="$2";;
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-s | --image-size) IMAGE_SIZE="$2";;
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-i | --initfs-features) INITFS_FEATURES="${INITFS_FEATURES:-} $2";;
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-k | --kernel-flavor) KERNEL_FLAVOR="$2";;
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--keys-dir) KEYS_DIR="$(realpath "$2")";;
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-C | --no-cleanup) CLEANUP='no'; n=1;;
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-p | --packages) PACKAGES="${PACKAGES:-} $2";;
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-r | --repositories-file) REPOS_FILE="$(realpath "$2")";;
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--rootfs) ROOTFS="$2";;
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-c | --script-chroot) SCRIPT_CHROOT='yes'; n=1;;
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-h | --help) help 0;;
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-V | --version) echo "$PROGNAME $VERSION"; exit 0;;
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--) shift; break;;
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esac
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shift $n
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done
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: ${CLEANUP:="yes"}
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: ${IMAGE_FORMAT:=}
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: ${IMAGE_SIZE:="2G"}
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: ${INITFS_FEATURES:="scsi virtio"}
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: ${KERNEL_FLAVOR:="virthardened"}
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: ${KEYS_DIR:="/etc/apk/keys"}
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: ${PACKAGES:=}
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: ${REPOS_FILE:="/etc/apk/repositories"}
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: ${ROOTFS:="ext4"}
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: ${SCRIPT_CHROOT:="no"}
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[ $# -ne 0 ] || help 1 >&2
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IMAGE_FILE="$1"; shift
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SCRIPT=
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[ $# -eq 0 ] || { SCRIPT=$(realpath "$1"); shift; }
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[ "$CLEANUP" = no ] || trap cleanup EXIT HUP INT TERM
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#-----------------------------------------------------------------------
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einfo 'Installing needed packages on host system'
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$APK add -t $VIRTUAL_PKG qemu qemu-img syslinux
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install_fs_tools "$ROOTFS"
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#-----------------------------------------------------------------------
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if [ ! -f "$IMAGE_FILE" ]; then
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einfo "Creating $IMAGE_FORMAT image of size $IMAGE_SIZE"
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qemu-img create ${IMAGE_FORMAT:+-f $IMAGE_FORMAT} "$IMAGE_FILE" "$IMAGE_SIZE"
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fi
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#-----------------------------------------------------------------------
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einfo "Attaching image $IMAGE_FILE as a NBD device"
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nbd_dev=$(attach_image "$IMAGE_FILE" "$IMAGE_FORMAT")
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#-----------------------------------------------------------------------
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einfo "Formatting image to $ROOTFS"
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# syslinux 6.0.3 cannot boot from ext4 w/ 64bit feature enabled
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[ "$ROOTFS" = ext4 ] && mkfs_args='-O ^64bit' || mkfs_args=''
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mkfs.$ROOTFS -L root $mkfs_args "$nbd_dev"
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root_uuid=$(blk_uuid "$nbd_dev")
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mount_dir=$(mktemp -d /tmp/$PROGNAME.XXXXXX)
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#-----------------------------------------------------------------------
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einfo "Mounting image at $mount_dir"
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mount "$nbd_dev" "$mount_dir"
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#-----------------------------------------------------------------------
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einfo 'Installing base system'
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cd "$mount_dir"
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mkdir -p etc/apk/keys
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install -m 644 "$REPOS_FILE" etc/apk/repositories
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cp "$KEYS_DIR"/* etc/apk/keys/
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$APK add --root . --update-cache --initdb alpine-base
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prepare_chroot .
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#-----------------------------------------------------------------------
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einfo "Installing and configuring mkinitfs"
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$APK add --root . mkinitfs
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setup_mkinitfs . "base $ROOTFS $INITFS_FEATURES"
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#-----------------------------------------------------------------------
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einfo "Installing kernel linux-$KERNEL_FLAVOR"
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$APK add --root . linux-$KERNEL_FLAVOR
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#-----------------------------------------------------------------------
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einfo 'Setting up extlinux bootloader'
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$APK add --root . --no-scripts syslinux
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setup_extlinux . "UUID=$root_uuid" $ROOTFS ${KERNEL_FLAVOR#virt}
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cat > etc/fstab <<-EOF
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# <fs> <mountpoint> <type> <opts> <dump/pass>
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UUID=$root_uuid / $ROOTFS noatime 0 1
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EOF
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#-----------------------------------------------------------------------
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einfo 'Enabling base system services'
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rc_add sysinit devfs dmesg mdev hwdrivers
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rc_add boot modules hwclock swap hostname sysctl bootmisc syslog
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rc_add shutdown killprocs savecache mount-ro
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#-----------------------------------------------------------------------
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if [ -n "$PACKAGES" ]; then
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einfo 'Installing additional packages'
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$APK add --root . $PACKAGES
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fi
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#-----------------------------------------------------------------------
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if [ -n "$SCRIPT" ]; then
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script_name="${SCRIPT##*/}"
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if [ "$SCRIPT_CHROOT" = 'no' ]; then
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einfo "Executing script: $script_name $@"
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"$SCRIPT" "$@" || die 'Script failed'
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else
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einfo "Executing script in chroot: $script_name $@"
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mount --bind "${SCRIPT%/*}" mnt/
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chroot . sh -c "cd /mnt && ./$script_name \"\$@\"" -- "$@" \
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|| die 'Script failed'
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fi
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fi
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#-----------------------------------------------------------------------
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einfo 'Completed'
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cd - >/dev/null
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ls -lh "$IMAGE_FILE"
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