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#!/bin/bash
# Create application containers from OCI images
# Copyright © 2014 Stéphane Graber <stgraber@ubuntu.com>
# Copyright © 2017 Serge Hallyn <serge@hallyn.com>
#
# This library is free software; you can redistribute it and/or
# modify it under the terms of the GNU Lesser General Public
# License as published by the Free Software Foundation; either
# version 2.1 of the License, or (at your option) any later version.
# This library is distributed in the hope that it will be useful,
# but WITHOUT ANY WARRANTY; without even the implied warranty of
# MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
# Lesser General Public License for more details.
# You should have received a copy of the GNU Lesser General Public
# License along with this library; if not, write to the Free Software
# Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301
# USA
set -eu
# Make sure the usual locations are in PATH
export PATH=$PATH:/usr/sbin:/usr/bin:/sbin:/bin
# Check for required binaries
for bin in skopeo umoci jq; do
if ! which $bin >/dev/null 2>&1; then
echo "ERROR: Missing required tool: $bin" 1>&2
exit 1
fi
done
LOCALSTATEDIR="/var"
LXC_TEMPLATE_CONFIG="/usr/share/lxc/config"
LXC_HOOK_DIR="/usr/share/lxc/hooks"
# Some useful functions
cleanup() {
if [ -d "${DOWNLOAD_TEMP}" ]; then
rm -Rf "${DOWNLOAD_TEMP}"
fi
if [ -d "${LXC_ROOTFS}.tmp" ]; then
rm -Rf "${LXC_ROOTFS}.tmp"
fi
}
in_userns() {
[ -e /proc/self/uid_map ] || { echo no; return; }
while read -r line; do
fields="$(echo "$line" | awk '{ print $1 " " $2 " " $3 }')"
if [ "${fields}" = "0 0 4294967295" ]; then
echo no;
return;
fi
if echo "${fields}" | grep -q " 0 1$"; then
echo userns-root;
return;
fi
done < /proc/self/uid_map
[ "$(cat /proc/self/uid_map)" = "$(cat /proc/1/uid_map)" ] && { echo userns-root; return; }
echo yes
}
getconfigpath() {
basedir="$1"
q="$2"
digest=$(jq -c -r --arg q "$q" '.manifests[] | if .annotations."org.opencontainers.image.ref.name" == $q then .digest else empty end' < "${basedir}/index.json")
if [ -z "${digest}" ]; then
echo "$q not found in index.json" >&2
return
fi
# Ok we have the image config digest, now get the config from that
# shellcheck disable=SC2039
d=${digest:7}
cdigest=$(jq -c -r '.config.digest' < "${basedir}/blobs/sha256/${d}")
if [ -z "${cdigest}" ]; then
echo "container config not found" >&2
return
fi
# shellcheck disable=SC2039
d2=${cdigest:7}
echo "${basedir}/blobs/sha256/${d2}"
return
}
# Get entrypoint from oci image. Use sh if unspecified
getep() {
if [ "$#" -eq 0 ]; then
echo "/bin/sh"
return
fi
configpath="$1"
ep=$(jq -c '.config.Entrypoint[]?'< "${configpath}" | tr '\n' ' ')
cmd=$(jq -c '.config.Cmd[]?'< "${configpath}" | tr '\n' ' ')
if [ -z "${ep}" ]; then
ep="${cmd}"
if [ -z "${ep}" ]; then
ep="/bin/sh"
fi
elif [ -n "${cmd}" ]; then
ep="${ep} ${cmd}"
fi
echo "${ep}"
return
}
# get environment from oci image.
getenv() {
if [ "$#" -eq 0 ]; then
return
fi
configpath="$1"
env=$(jq -c -r '.config.Env[]'< "${configpath}")
echo "${env}"
return
}
# check var is decimal.
isdecimal() {
var="$1"
if [ "${var}" -eq "${var}" ] 2> /dev/null; then
return 0
else
return 1
fi
}
# get uid, gid from oci image.
getuidgid() {
configpath="$1"
rootpath="$2"
passwdpath="${rootpath}/etc/passwd"
grouppath="${rootpath}/etc/group"
usergroup=$(jq -c -r '.config.User' < "${configpath}")
# shellcheck disable=SC2039
usergroup=(${usergroup//:/ })
user=${usergroup[0]:-0}
if ! isdecimal "${user}"; then
if [ -f ${passwdpath} ]; then
user=$(grep "^${user}:" "${passwdpath}" | awk -F: '{print $3}')
else
user=0
fi
fi
group=${usergroup[1]:-}
if [ -z "${group}" ]; then
if [ -f "${passwdpath}" ]; then
group=$(grep "^[^:]*:[^:]*:${user}:" "${passwdpath}" | awk -F: '{print $4}')
else
group=0
fi
elif ! isdecimal "${group}"; then
if [ -f "${grouppath}" ]; then
group=$(grep "^${group}:" "${grouppath}" | awk -F: '{print $3}')
else
group=0
fi
fi
echo "${user:-0} ${group:-0}"
return
}
# get cwd from oci image.
getcwd() {
if [ "$#" -eq 0 ]; then
echo "/"
return
fi
configpath="$1"
cwd=$(jq -c -r '.config.WorkingDir // "/"' < "${configpath}")
echo "${cwd}"
return
}
usage() {
cat <<EOF
LXC container template for OCI images
Special arguments:
[ -h | --help ]: Print this help message and exit.
Required arguments:
[ -u | --url <url> ]: The OCI image URL
Optional arguments:
[ --username <username> ]: The username for the registry
[ --password <password> ]: The password for the registry
LXC internal arguments (do not pass manually!):
[ --name <name> ]: The container name
[ --path <path> ]: The path to the container
[ --rootfs <rootfs> ]: The path to the container's rootfs
[ --mapped-uid <map> ]: A uid map (user namespaces)
[ --mapped-gid <map> ]: A gid map (user namespaces)
EOF
return 0
}
if ! options=$(getopt -o u:h -l help,url:,username:,password:,no-cache,dhcp,name:,path:,rootfs:,mapped-uid:,mapped-gid: -- "$@"); then
usage
exit 1
fi
eval set -- "$options"
OCI_URL=""
OCI_USERNAME=
OCI_PASSWORD=
OCI_USE_CACHE="true"
OCI_USE_DHCP="false"
LXC_MAPPED_GID=
LXC_MAPPED_UID=
LXC_NAME=
LXC_PATH=
LXC_ROOTFS=
while :; do
case "$1" in
-h|--help) usage && exit 1;;
-u|--url) OCI_URL=$2; shift 2;;
--username) OCI_USERNAME=$2; shift 2;;
--password) OCI_PASSWORD=$2; shift 2;;
--no-cache) OCI_USE_CACHE="false"; shift 1;;
--dhcp) OCI_USE_DHCP="true"; shift 1;;
--name) LXC_NAME=$2; shift 2;;
--path) LXC_PATH=$2; shift 2;;
--rootfs) LXC_ROOTFS=$2; shift 2;;
--mapped-uid) LXC_MAPPED_UID=$2; shift 2;;
--mapped-gid) LXC_MAPPED_GID=$2; shift 2;;
*) break;;
esac
done
# Check that we have all variables we need
if [ -z "$LXC_NAME" ] || [ -z "$LXC_PATH" ] || [ -z "$LXC_ROOTFS" ]; then
echo "ERROR: Not running through LXC" 1>&2
exit 1
fi
if [ -z "$OCI_URL" ]; then
echo "ERROR: no OCI URL given"
exit 1
fi
if [ -n "$OCI_PASSWORD" ] && [ -z "$OCI_USERNAME" ]; then
echo "ERROR: password given but no username specified"
exit 1
fi
if [ "${OCI_USE_CACHE}" = "true" ]; then
if ! skopeo copy --help | grep -q 'dest-shared-blob-dir'; then
echo "INFO: skopeo doesn't support blob caching"
OCI_USE_CACHE="false"
fi
fi
USERNS=$(in_userns)
if [ "$USERNS" = "yes" ]; then
if [ -z "$LXC_MAPPED_UID" ] || [ "$LXC_MAPPED_UID" = "-1" ]; then
echo "ERROR: In a user namespace without a map" 1>&2
exit 1
fi
fi
if [ "${OCI_USE_CACHE}" = "true" ]; then
if [ "$USERNS" = "yes" ]; then
DOWNLOAD_BASE="${HOME}/.cache/lxc"
else
DOWNLOAD_BASE="${LOCALSTATEDIR}/cache/lxc"
fi
else
DOWNLOAD_BASE=/tmp
fi
mkdir -p "${DOWNLOAD_BASE}"
# Trap all exit signals
trap cleanup EXIT HUP INT TERM
if ! which mktemp >/dev/null 2>&1; then
DOWNLOAD_TEMP="${DOWNLOAD_BASE}/lxc-oci.$$"
mkdir -p "${DOWNLOAD_TEMP}"
else
DOWNLOAD_TEMP=$(mktemp -d -p "${DOWNLOAD_BASE}")
fi
# Download the image
# shellcheck disable=SC2039
skopeo_args=("")
if [ -n "$OCI_USERNAME" ]; then
CREDENTIALS="${OCI_USERNAME}"
if [ -n "$OCI_PASSWORD" ]; then
CREDENTIALS="${CREDENTIALS}:${OCI_PASSWORD}"
fi
# shellcheck disable=SC2039
skopeo_args+=(--src-creds "${CREDENTIALS}")
fi
if [ "${OCI_USE_CACHE}" = "true" ]; then
# shellcheck disable=SC2039
# shellcheck disable=SC2068
skopeo_args+=(--dest-shared-blob-dir "${DOWNLOAD_BASE}")
# shellcheck disable=SC2039
# shellcheck disable=SC2068
skopeo copy ${skopeo_args[@]} "${OCI_URL}" "oci:${DOWNLOAD_TEMP}:latest"
ln -s "${DOWNLOAD_BASE}/sha256" "${DOWNLOAD_TEMP}/blobs/sha256"
else
# shellcheck disable=SC2039
# shellcheck disable=SC2068
skopeo copy ${skopeo_args[@]} "${OCI_URL}" "oci:${DOWNLOAD_TEMP}:latest"
fi
echo "Unpacking the rootfs"
# shellcheck disable=SC2039
umoci_args=("")
if [ -n "$LXC_MAPPED_UID" ] && [ "$LXC_MAPPED_UID" != "-1" ]; then
# shellcheck disable=SC2039
umoci_args+=(--rootless)
fi
# shellcheck disable=SC2039
# shellcheck disable=SC2068
umoci --log=error unpack ${umoci_args[@]} --image "${DOWNLOAD_TEMP}:latest" "${LXC_ROOTFS}.tmp"
rmdir "${LXC_ROOTFS}"
mv "${LXC_ROOTFS}.tmp/rootfs" "${LXC_ROOTFS}"
OCI_CONF_FILE=$(getconfigpath "${DOWNLOAD_TEMP}" latest)
LXC_CONF_FILE="${LXC_PATH}/config"
entrypoint=$(getep "${OCI_CONF_FILE}")
echo "lxc.execute.cmd = '${entrypoint}'" >> "${LXC_CONF_FILE}"
echo "lxc.mount.auto = proc:mixed sys:mixed cgroup:mixed" >> "${LXC_CONF_FILE}"
environment=$(getenv "${OCI_CONF_FILE}")
# shellcheck disable=SC2039
while read -r line; do
echo "lxc.environment = ${line}" >> "${LXC_CONF_FILE}"
done <<< "${environment}"
if [ -e "${LXC_TEMPLATE_CONFIG}/common.conf" ]; then
echo "lxc.include = ${LXC_TEMPLATE_CONFIG}/common.conf" >> "${LXC_CONF_FILE}"
fi
if [ -n "$LXC_MAPPED_UID" ] && [ "$LXC_MAPPED_UID" != "-1" ] && [ -e "${LXC_TEMPLATE_CONFIG}/userns.conf" ]; then
echo "lxc.include = ${LXC_TEMPLATE_CONFIG}/userns.conf" >> "${LXC_CONF_FILE}"
fi
if [ -e "${LXC_TEMPLATE_CONFIG}/oci.common.conf" ]; then
echo "lxc.include = ${LXC_TEMPLATE_CONFIG}/oci.common.conf" >> "${LXC_CONF_FILE}"
fi
if [ "${OCI_USE_DHCP}" = "true" ]; then
echo "lxc.hook.start-host = ${LXC_HOOK_DIR}/dhclient" >> "${LXC_CONF_FILE}"
echo "lxc.hook.stop = ${LXC_HOOK_DIR}/dhclient" >> "${LXC_CONF_FILE}"
fi
echo "lxc.uts.name = ${LXC_NAME}" >> "${LXC_CONF_FILE}"
# set the hostname
cat <<EOF > "${LXC_ROOTFS}/etc/hostname"
${LXC_NAME}
EOF
# set minimal hosts
cat <<EOF > "${LXC_ROOTFS}/etc/hosts"
127.0.0.1 localhost
127.0.1.1 ${LXC_NAME}
::1 localhost ip6-localhost ip6-loopback
fe00::0 ip6-localnet
ff00::0 ip6-mcastprefix
ff02::1 ip6-allnodes
ff02::2 ip6-allrouters
EOF
# shellcheck disable=SC2039
uidgid=($(getuidgid "${OCI_CONF_FILE}" "${LXC_ROOTFS}" ))
# shellcheck disable=SC2039
echo "lxc.init.uid = ${uidgid[0]}" >> "${LXC_CONF_FILE}"
# shellcheck disable=SC2039
echo "lxc.init.gid = ${uidgid[1]}" >> "${LXC_CONF_FILE}"
cwd=$(getcwd "${OCI_CONF_FILE}")
echo "lxc.init.cwd = ${cwd}" >> "${LXC_CONF_FILE}"
if [ -n "$LXC_MAPPED_UID" ] && [ "$LXC_MAPPED_UID" != "-1" ]; then
chown "$LXC_MAPPED_UID" "$LXC_PATH/config" "$LXC_PATH/fstab" > /dev/null 2>&1 || true
fi
if [ -n "$LXC_MAPPED_GID" ] && [ "$LXC_MAPPED_GID" != "-1" ]; then
chgrp "$LXC_MAPPED_GID" "$LXC_PATH/config" "$LXC_PATH/fstab" > /dev/null 2>&1 || true
fi
exit 0
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