Merge "Add script to customize Ubuntu guest images."
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Zuul
Gerrit Code Review
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#!/bin/bash
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# IMPLEMENTATION NOTE: It was not possible to implement this script using
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# virt-customize because of below ubuntu bugs:
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# - https://bugs.launchpad.net/ubuntu/+source/libguestfs/+bug/1632405
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# - https://bugs.launchpad.net/ubuntu/+source/isc-dhcp/+bug/1650740
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#
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# It has therefore been adopted a more low level strategy performing below
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# steps:
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# - mount guest image to a temporary folder
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# - set up an environment suitable for executing chroot
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# - execute customize_image function inside chroot environment
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# - cleanup chroot environment
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# Array of packages to be installed of guest image
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INSTALL_GUEST_PACKAGES=(
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socat # used to replace nc for testing advanced network features like
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# multicast
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)
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# Function to be executed once after chroot on guest image
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# Add more customization steps here
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function customize_image {
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# dhclient-script requires to read /etc/fstab for setting up network
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touch /etc/fstab
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chmod ugo+r /etc/fstab
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# Ubuntu guest image _apt user could require access to below folders
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local apt_user_folders=( /var/lib/apt/lists/partial )
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mkdir -p "${apt_user_folders[@]}"
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chown _apt.root -fR "${apt_user_folders[@]}"
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# Install desired packages to Ubuntu guest image
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apt-get update -y
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apt-get install -y "${INSTALL_GUEST_PACKAGES[@]}"
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}
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function main {
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set -eux
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trap cleanup EXIT
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"${ENTRY_POINT:-chroot_image}" "$@"
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}
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# Chroot to guest image then executes customize_image function inside it
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function chroot_image {
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local image_file=$1
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local temp_dir=${TEMP_DIR:-$(make_temp -d)}
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# Mount guest image into a temporary directory
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local mount_dir=${temp_dir}/mount
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mkdir -p "${mount_dir}"
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mount_image "${mount_dir}" "${temp_dir}/pid"
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# Mount system directories
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bind_dir "/dev" "${mount_dir}/dev"
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bind_dir "/dev/pts" "${mount_dir}/dev/pts"
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bind_dir "/proc" "${mount_dir}/proc"
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bind_dir "/sys" "${mount_dir}/sys"
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# Mount to keep temporary files out of guest image
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mkdir -p "${temp_dir}/apt" "${temp_dir}/cache" "${temp_dir}/tmp"
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bind_dir "${temp_dir}/cache" "${mount_dir}/var/cache"
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bind_dir "${temp_dir}/tmp" "${mount_dir}/tmp"
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bind_dir "${temp_dir}/tmp" "${mount_dir}/var/tmp"
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bind_dir "${temp_dir}/apt" "${mount_dir}/var/lib/apt"
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# Replace /etc/resolv.conf symlink to use the same DNS as this host
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sudo rm -f "${mount_dir}/etc/resolv.conf"
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sudo cp /etc/resolv.conf "${mount_dir}/etc/resolv.conf"
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# Makesure /etc/fstab exists and it is readable because it is required by
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# /sbin/dhclient-script
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sudo touch /etc/fstab
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sudo chmod 644 /etc/fstab
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# Copy this script to mount dir
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local script_name=$(basename "$0")
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local script_file=${mount_dir}/${script_name}
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sudo cp "$0" "${script_file}"
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sudo chmod 500 "${script_file}"
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add_cleanup sudo rm -f "'${script_file}'"
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# Execute customize_image inside chroot environment
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local command_line=( ${CHROOT_COMMAND:-customize_image} )
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local entry_point=${command_line[0]}
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unset command_line[0]
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sudo -E "ENTRY_POINT=${entry_point}" \
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chroot "${mount_dir}" "/${script_name}" "${command_line[@]:-}"
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}
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# Mounts guest image to $1 directory writing pid to $1 pid file
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# Then registers umount of such directory for final cleanup
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function mount_image {
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local mount_dir=$1
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local pid_file=$2
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# export libguest settings
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export LIBGUESTFS_BACKEND=${LIBGUESTFS_BACKEND:-direct}
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export LIBGUESTFS_BACKEND_SETTINGS=${LIBGUESTFS_BACKEND_SETTINGS:-force_tcg}
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# Mount guest image
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sudo -E guestmount -i \
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--add "${image_file}" \
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--pid-file "${pid_file}" \
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"${mount_dir}"
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add_cleanup \
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'ENTRY_POINT=umount_image' \
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"'$0'" "'${mount_dir}'" "'${pid_file}'"
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}
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# Unmounts guest image directory
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function umount_image {
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local mount_dir=$1
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local pid_file=$2
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local timeout=10
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# Take PID just before unmounting
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local pid=$(cat ${pid_file} || true)
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sudo -E guestunmount "${mount_dir}"
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if [ "${pid:-}" != "" ]; then
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# Make sure guestmount process is not running before using image
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# file again
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local count=${timeout}
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while sudo kill -0 "${pid}" 2> /dev/null && (( count-- > 0 )); do
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sleep 1
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done
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if [ ${count} == 0 ]; then
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# It is not safe to use image file at this point
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echo "Wait for guestmount to exit failed after ${timeout} seconds"
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fi
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fi
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}
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# Creates a temporary file or directory and register removal for final cleanup
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function make_temp {
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local temporary=$(mktemp "$@")
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add_cleanup sudo rm -fR "'${temporary}'"
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echo "${temporary}"
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}
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# Bind directory $1 to directory $2 and register umount for final cleanup
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function bind_dir {
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local source_dir=$1
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local target_dir=$2
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sudo mount --bind "${source_dir}" "${target_dir}"
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add_cleanup sudo umount "'${target_dir}'"
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}
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# Registers a command line to be executed for final cleanup
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function add_cleanup {
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CLEANUP_FILE=${CLEANUP_FILE:-$(mktemp)}
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echo -e "$*" >> ${CLEANUP_FILE}
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}
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# Execute command lines for final cleanup in reversed order
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function cleanup {
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error=$?
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local cleanup_file=${CLEANUP_FILE:-}
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if [ -r "${cleanup_file}" ]; then
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tac "${cleanup_file}" | bash +e -x
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CLEANUP_FILE=
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rm -fR "${cleanup_file}"
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fi
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exit ${error}
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}
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main "$@"
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