ansible/docker/run_chroot.sh - onap/oom/offline-installer - Gitiles

 #!/bin/sh

 #   COPYRIGHT NOTICE STARTS HERE

 #   Copyright 2018 © Samsung Electronics Co., Ltd.
 #
 #   Licensed under the Apache License, Version 2.0 (the "License");
 #   you may not use this file except in compliance with the License.
 #   You may obtain a copy of the License at
 #
 #       http://www.apache.org/licenses/LICENSE-2.0
 #
 #   Unless required by applicable law or agreed to in writing, software
 #   distributed under the License is distributed on an "AS IS" BASIS,
 #   WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
 #   See the License for the specific language governing permissions and
 #   limitations under the License.

 #   COPYRIGHT NOTICE ENDS HERE


 set -e

 CMD=$(basename "$0")
 UMOUNT_TIMEOUT=120 # 2mins


 #
 # functions
 #

 help()
 {
     echo "
 NAME:
     ${CMD} - run command in chrooted directory

 DESCRIPTION:
     It will do necessary steps to be able chroot, optional mounts and it will
     run commands inside the requested chroot directory.

     It does overlay mount so nothing inside the chroot is modified - if there
     is no way to do overlay mount it will just do chroot directly - which means
     that user has power to render chroot useless - beware...

     The chroot is run in it's own namespace for better containerization.
     Therefore the utility 'unshare' is necessary requirement.

     After exiting the chroot all of those necessary steps are undone.

 USAGE:
     ${CMD} [-h|--help|help]
         This help

     ${CMD} [OPTIONS] execute <chroot-directory> [<command with args>...]

         It will do some necessary steps after which it will execute chroot
         command and gives you prompt inside the chroot. When you leave the
         prompt it will undo those steps.
         On top of the ordinary chroot it will make overlay, so every change
         inside the chroot is only temporary and chroot is kept stateless -
         like inside a docker container. If there is no way to do overlay -
         ordinary chroot is done.
         Default command is: /bin/sh -l

         OPTIONS:

         --mount (ro|rw):<src-dir>:<inner-dir>
             This option will mount 'src-dir' which is full path on the host
             system into the relative path 'inner-dir' within the chroot
             directory.
             It can be mounted as read-only (ro) or read-write (rw).
             Multiple usage of this argument can be used to create complex
             hierarchy. Order is significant.
             For example:
                 --mount ro:/scripts/ANSIBLE_DIR:/ansible \
                 --mount rw:/scripts/ANSIBLE_DIR/app:/ansible/app
                 This will mount directory ansible as read-only into chroot,
                 but it's subdirectory 'app' will be writeable.

         --workdir <inner-dir>
             This will set working directory (PWD) inside the chroot.

 EXAMPLE:
     ${CMD} --mount ro:/scripts/ansible:ansible \
         --mount rw:/scripts/ansible/app:ansible/app \
         --workdir /ansible execute /tmp/ansible_chroot
     # pwd
     /ansible
     # mount
     overlay on / type overlay ...
     /dev/disk on /ansible type ext4 (ro,relatime,errors=remount-ro)
     /dev/disk on /ansible/application type ext4 (rw,relatime,errors=remount-ro)
     none on /proc type proc (rw,relatime)
     none on /sys type sysfs (rw,relatime)
     none on /dev/shm type tmpfs (rw,relatime)

     Directory /ansible inside the chroot is not writable but subdirectory
     /ansible/app is.

     Rest of the chroot is under overlay and all changes will be lost when
     chroot command ends. Only changes in app directory persists bacause it
     was bind mounted as read-write and is not part of overlay.

     Note: as you can see app directory is mounted over itself but read-write.
 "
 }

 # arg: <directory>
 is_mounted()
 {
     mountpoint=$(echo "$1" | sed 's#//*#/#g')

     LANG=C mount | grep -q "^[^[:space:]]\+[[:space:]]\+on[[:space:]]\+${mountpoint}[[:space:]]\+type[[:space:]]\+"
 }

 # layers are right to left! First is on the right, top/last is on the left
 do_overlay_mount()
 {
     if [ -d "$overlay" ] && is_mounted "$overlay" ; then
         echo ERROR: "The overlay directory is already mounted: $overlay" >&2
         echo ERROR: "Fix the issue - cannot proceed" >&2
         exit 1
     fi

     # prepare dirs
     rm -rf "$overlay" "$upperdir" "$workdir"
     mkdir -p "$overlay"
     mkdir -p "$upperdir"
     mkdir -p "$workdir"

     # finally overlay mount
     if ! mount -t overlay --make-rprivate \
         -o lowerdir="$lowerdir",upperdir="$upperdir",workdir="$workdir" \
         overlay "$overlay" ;
     then
         echo ERROR: "Failed to do overlay mount!" >&2
         echo ERROR: "Please check that your system supports overlay!" >&2
         echo NOTE: "Continuing with the ordinary chroot without overlay!"

         CHROOT_DIR="$lowerdir"
         return 1
     fi

     CHROOT_DIR="$overlay"

     return 0
 }

 cleanup()
 {
     case "$OVERLAY_MOUNT" in
         yes)
             echo INFO: "Umounting overlay..." >&2
             if ! umount_retry "$CHROOT_DIR" ; then
                 echo ERROR: "Cannot umount chroot: $CHROOT_DIR" >&2
                 return 1
             fi

             ;;
         no)
             echo INFO: "No overlay to umount" >&2
             ;;
     esac

     if ! is_mounted "$overlay" ; then
         echo INFO: "Deleting of temp directories..." >&2
         rm -rf "$overlay" "$upperdir" "$workdir"
     else
         echo ERROR: "Overlay is still mounted: $CHROOT_DIR" >&2
         echo ERROR: "Cannot delete: $overlay" >&2
         echo ERROR: "Cannot delete: $upperdir" >&2
         echo ERROR: "Cannot delete: $workdir" >&2
         return 1
     fi
 }

 check_external_mounts()
 {
     echo "$EXTERNAL_MOUNTS" | sed '/^[[:space:]]*$/d' | while read -r mountexpr ; do
         mount_type=$(echo "$mountexpr" | awk 'BEGIN{FS=":"}{print $1;}')
         external=$(echo "$mountexpr" | awk 'BEGIN{FS=":"}{print $2;}')
         internal=$(echo "$mountexpr" | awk 'BEGIN{FS=":"}{print $3;}' | sed -e 's#^/*##' -e 's#//*#/#g')

         case "$mount_type" in
             ro|rw)
                 :
                 ;;
             *)
                 echo ERROR: "Wrong mount type (should be 'ro' or 'rw') in: ${mountexpr}" >&2
                 exit 1
                 ;;
         esac

         if ! [ -d "$external" ] ; then
             echo ERROR: "Directory for mounting does not exist: ${external}" >&2
             exit 1
         fi

         if echo "$internal" | grep -q '^/*$' ; then
             echo ERROR: "Unacceptable internal path: ${internal}" >&2
             exit 1
         fi
     done
 }

 do_external_mounts()
 {
     echo INFO: "Bind mounting of external mounts..." >&2
     echo "$EXTERNAL_MOUNTS" | sed '/^[[:space:]]*$/d' | while read -r mountexpr ; do
         mount_type=$(echo "$mountexpr" | awk 'BEGIN{FS=":"}{print $1;}')
         external=$(echo "$mountexpr" | awk 'BEGIN{FS=":"}{print $2;}')
         internal=$(echo "$mountexpr" | awk 'BEGIN{FS=":"}{print $3;}' | sed -e 's#^/*##' -e 's#//*#/#g')

         if is_mounted "${CHROOT_DIR}/${internal}" ; then
             echo ERROR: "Mountpoint is already mounted: ${CHROOT_DIR}/${internal}" >&2
             echo ERROR: "Fix the issue - cannot proceed" >&2
             exit 1
         fi

         if ! mkdir -p "${CHROOT_DIR}/${internal}" ; then
             echo ERROR: "Cannot create mountpoint: ${CHROOT_DIR}/${internal}" >&2
             exit 1
         fi

         if ! mount --make-rprivate -o bind,${mount_type} "$external" "${CHROOT_DIR}/${internal}" ; then
             echo ERROR: "Failed to mount: ${external} -> ${internal}" >&2
             exit 1
         else
             echo INFO: "Mount: ${external} -> ${internal}" >&2
         fi
     done
 }

 # arg: <mountpoint>
 umount_retry()
 {
     mountpoint=$(echo "$1" | sed 's#//*#/#g')
     timeout=${UMOUNT_TIMEOUT}

     umount "$mountpoint" 2>/dev/null
     while is_mounted "$mountpoint" && [ $timeout -gt 0 ] ; do
         umount "$mountpoint" 2>/dev/null
         sleep 1
         timeout=$(( timeout - 1 ))
     done

     if ! is_mounted "$mountpoint" ; then
         return 0
     fi

     return 1
 }

 undo_external_mounts()
 {
     echo INFO: "Umount external mount points..." >&2
     echo "$EXTERNAL_MOUNTS" | tac | sed '/^[[:space:]]*$/d' | while read -r mountexpr ; do
         mount_type=$(echo "$mountexpr" | awk 'BEGIN{FS=":"}{print $1;}')
         external=$(echo "$mountexpr" | awk 'BEGIN{FS=":"}{print $2;}')
         internal=$(echo "$mountexpr" | awk 'BEGIN{FS=":"}{print $3;}' | sed -e 's#^/*##' -e 's#//*#/#g')
         if umount_retry "${CHROOT_DIR}/${internal}" ; then
             echo INFO: "Unmounted: ${CHROOT_DIR}/${internal}" >&2
         else
             echo ERROR: "Failed to umount: ${CHROOT_DIR}/${internal}" >&2
         fi
     done
 }

 install_wrapper()
 {
     cat > "$CHROOT_DIR"/usr/local/bin/fakeshell.sh <<EOF
 #!/bin/sh

 PATH=/usr/local/sbin:/usr/local/bin:/usr/sbin:/usr/bin:/sbin:/bin
 export PATH

 gid_tty=\$(getent group | sed -n '/^tty:/p' | cut -d: -f 3)

 mount -t proc proc /proc
 mount -t sysfs none /sys
 mount -t tmpfs none /dev

 mkdir -p /dev/shm
 mkdir -p /dev/pts
 mount -t devpts -o gid=\${gid_tty},mode=620 none /dev/pts

 [ -e /dev/full ] || mknod -m 666 /dev/full c 1 7
 [ -e /dev/ptmx ] || mknod -m 666 /dev/ptmx c 5 2
 [ -e /dev/random ] || mknod -m 644 /dev/random c 1 8
 [ -e /dev/urandom ] || mknod -m 644 /dev/urandom c 1 9
 [ -e /dev/zero ] || mknod -m 666 /dev/zero c 1 5
 [ -e /dev/tty ] || mknod -m 666 /dev/tty c 5 0
 [ -e /dev/console ] || mknod -m 622 /dev/console c 5 1
 [ -e /dev/null ] || mknod -m 666 /dev/null c 1 3

 chown root:tty /dev/console
 chown root:tty /dev/ptmx
 chown root:tty /dev/tty

 mkdir -p "\$1" || exit 1
 cd "\$1" || exit 1
 shift

 exec "\$@"

 EOF
     chmod +x "$CHROOT_DIR"/usr/local/bin/fakeshell.sh
 }

 on_exit()
 {
     set +e
     echo

     if [ -n "$OVERLAY_MOUNT" ] ; then
         undo_external_mounts
     fi
     cleanup
 }


 #
 # parse arguments
 #

 state=nil
 action=nil
 EXTERNAL_MOUNTS=''
 CHROOT_WORKDIR=''
 CHROOT_METADIR=''
 CHROOT_DIR=''
 COMMAND=''
 while [ -n "$1" ] ; do
     case "$state" in
         nil)
             case "$1" in
                 ''|-h|--help|help)
                     help
                     exit 0
                     ;;
                 --mount)
                     EXTERNAL_MOUNTS=$(printf "%s\n%s\n" "$EXTERNAL_MOUNTS" "${2}")
                     state=next
                     ;;
                 --workdir)
                     if [ -z "$CHROOT_WORKDIR" ] ; then
                         CHROOT_WORKDIR="$2"
                         state=next
                     else
                         echo ERROR: "Multiple working directory argument" >&2
                         help >&2
                         exit 1
                     fi
                     ;;
                 execute)
                     action=execute
                     state=execute
                     ;;
                 *)
                     echo ERROR: "Bad usage" >&2
                     help >&2
                     exit 1
                     ;;
             esac
             ;;
         next)
             state=nil
             ;;
         execute)
             CHROOT_METADIR="$1"
             shift
             break
             ;;
     esac
     shift
 done


 case "$action" in
     ''|nil)
         echo ERROR: "Nothing to do - missing command" >&2
         help >&2
         exit 1
         ;;
     execute)
         # firstly do sanity checking ...

         if [ -z "$CHROOT_METADIR" ] ; then
             echo ERROR: "Missing argument" >&2
             help >&2
             exit 1
         fi

         # making sure that CHROOT_METADIR is absolute path
         CHROOT_METADIR=$(readlink -f "$CHROOT_METADIR")

         if ! [ -d "$CHROOT_METADIR"/chroot ] ; then
             echo ERROR: "Filepath does not exist: ${CHROOT_METADIR}/chroot" >&2
             exit 1
         fi

         # check external mounts if there are any
         check_external_mounts

         # check workdir
         if [ -n "$CHROOT_WORKDIR" ] ; then
             CHROOT_WORKDIR=$(echo "$CHROOT_WORKDIR" | sed -e 's#^/*##' -e 's#//*#/#g')
         fi

         # we must be root
         if [ "$(id -u)" -ne 0 ] ; then
             echo ERROR: "Need to be root and you are not: $(id -nu)" >&2
             exit 1
         fi

         if ! which unshare >/dev/null 2>/dev/null ; then
             echo ERROR: "'unshare' system command is missing - ABORT" >&2
             echo INFO: "Try to install 'util-linux' package" >&2
             exit 1
         fi

         # ... sanity checking done

         # setup paths
         lowerdir="$CHROOT_METADIR"/chroot
         upperdir="$CHROOT_METADIR"/.overlay
         workdir="$CHROOT_METADIR"/.workdir
         overlay="$CHROOT_METADIR"/.merged

         # set trap
         trap on_exit QUIT TERM EXIT

         # mount overlay
         OVERLAY_MOUNT=''
         if do_overlay_mount ; then
             # overlay chroot
             OVERLAY_MOUNT=yes
         else
             # non overlay mount
             OVERLAY_MOUNT=no
         fi

         # do the user-specific mounts
         do_external_mounts

         # I need this wrapper to do some setup inside the chroot...
         install_wrapper

         # execute chroot
         # copy resolv.conf
         cp -a /etc/resolv.conf "$CHROOT_DIR"/etc/resolv.conf

         if [ -n "$1" ] ; then
             :
         else
             set -- /bin/sh -l
         fi
         unshare -mfpi --propagation private \
             chroot "$CHROOT_DIR" /usr/local/bin/fakeshell.sh "${CHROOT_WORKDIR:-/}" "$@"
         ;;
 esac

 exit 0
	#!/bin/sh

	# COPYRIGHT NOTICE STARTS HERE

	# Copyright 2018 © Samsung Electronics Co., Ltd.
	#
	# Licensed under the Apache License, Version 2.0 (the "License");
	# you may not use this file except in compliance with the License.
	# You may obtain a copy of the License at
	#
	# http://www.apache.org/licenses/LICENSE-2.0
	#
	# Unless required by applicable law or agreed to in writing, software
	# distributed under the License is distributed on an "AS IS" BASIS,
	# WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
	# See the License for the specific language governing permissions and
	# limitations under the License.

	# COPYRIGHT NOTICE ENDS HERE


	set -e

	CMD=$(basename "$0")
	UMOUNT_TIMEOUT=120 # 2mins


	#
	# functions
	#

	help()
	{
	echo "
	NAME:
	${CMD} - run command in chrooted directory

	DESCRIPTION:
	It will do necessary steps to be able chroot, optional mounts and it will
	run commands inside the requested chroot directory.

	It does overlay mount so nothing inside the chroot is modified - if there
	is no way to do overlay mount it will just do chroot directly - which means
	that user has power to render chroot useless - beware...

	The chroot is run in it's own namespace for better containerization.
	Therefore the utility 'unshare' is necessary requirement.

	After exiting the chroot all of those necessary steps are undone.

	USAGE:
	${CMD} [-h\|--help\|help]
	This help

	${CMD} [OPTIONS] execute <chroot-directory> [<command with args>...]

	It will do some necessary steps after which it will execute chroot
	command and gives you prompt inside the chroot. When you leave the
	prompt it will undo those steps.
	On top of the ordinary chroot it will make overlay, so every change
	inside the chroot is only temporary and chroot is kept stateless -
	like inside a docker container. If there is no way to do overlay -
	ordinary chroot is done.
	Default command is: /bin/sh -l

	OPTIONS:

	--mount (ro\|rw):<src-dir>:<inner-dir>
	This option will mount 'src-dir' which is full path on the host
	system into the relative path 'inner-dir' within the chroot
	directory.
	It can be mounted as read-only (ro) or read-write (rw).
	Multiple usage of this argument can be used to create complex
	hierarchy. Order is significant.
	For example:
	--mount ro:/scripts/ANSIBLE_DIR:/ansible \
	--mount rw:/scripts/ANSIBLE_DIR/app:/ansible/app
	This will mount directory ansible as read-only into chroot,
	but it's subdirectory 'app' will be writeable.

	--workdir <inner-dir>
	This will set working directory (PWD) inside the chroot.

	EXAMPLE:
	${CMD} --mount ro:/scripts/ansible:ansible \
	--mount rw:/scripts/ansible/app:ansible/app \
	--workdir /ansible execute /tmp/ansible_chroot
	# pwd
	/ansible
	# mount
	overlay on / type overlay ...
	/dev/disk on /ansible type ext4 (ro,relatime,errors=remount-ro)
	/dev/disk on /ansible/application type ext4 (rw,relatime,errors=remount-ro)
	none on /proc type proc (rw,relatime)
	none on /sys type sysfs (rw,relatime)
	none on /dev/shm type tmpfs (rw,relatime)

	Directory /ansible inside the chroot is not writable but subdirectory
	/ansible/app is.

	Rest of the chroot is under overlay and all changes will be lost when
	chroot command ends. Only changes in app directory persists bacause it
	was bind mounted as read-write and is not part of overlay.

	Note: as you can see app directory is mounted over itself but read-write.
	"
	}

	# arg: <directory>
	is_mounted()
	{
	mountpoint=$(echo "$1" \| sed 's#//*#/#g')

	LANG=C mount \| grep -q "^[^[:space:]]\+[[:space:]]\+on[[:space:]]\+${mountpoint}[[:space:]]\+type[[:space:]]\+"
	}

	# layers are right to left! First is on the right, top/last is on the left
	do_overlay_mount()
	{
	if [ -d "$overlay" ] && is_mounted "$overlay" ; then
	echo ERROR: "The overlay directory is already mounted: $overlay" >&2
	echo ERROR: "Fix the issue - cannot proceed" >&2
	exit 1
	fi

	# prepare dirs
	rm -rf "$overlay" "$upperdir" "$workdir"
	mkdir -p "$overlay"
	mkdir -p "$upperdir"
	mkdir -p "$workdir"

	# finally overlay mount
	if ! mount -t overlay --make-rprivate \
	-o lowerdir="$lowerdir",upperdir="$upperdir",workdir="$workdir" \
	overlay "$overlay" ;
	then
	echo ERROR: "Failed to do overlay mount!" >&2
	echo ERROR: "Please check that your system supports overlay!" >&2
	echo NOTE: "Continuing with the ordinary chroot without overlay!"

	CHROOT_DIR="$lowerdir"
	return 1
	fi

	CHROOT_DIR="$overlay"

	return 0
	}

	cleanup()
	{
	case "$OVERLAY_MOUNT" in
	yes)
	echo INFO: "Umounting overlay..." >&2
	if ! umount_retry "$CHROOT_DIR" ; then
	echo ERROR: "Cannot umount chroot: $CHROOT_DIR" >&2
	return 1
	fi

	;;
	no)
	echo INFO: "No overlay to umount" >&2
	;;
	esac

	if ! is_mounted "$overlay" ; then
	echo INFO: "Deleting of temp directories..." >&2
	rm -rf "$overlay" "$upperdir" "$workdir"
	else
	echo ERROR: "Overlay is still mounted: $CHROOT_DIR" >&2
	echo ERROR: "Cannot delete: $overlay" >&2
	echo ERROR: "Cannot delete: $upperdir" >&2
	echo ERROR: "Cannot delete: $workdir" >&2
	return 1
	fi
	}

	check_external_mounts()
	{
	echo "$EXTERNAL_MOUNTS" \| sed '/^[[:space:]]*$/d' \| while read -r mountexpr ; do
	mount_type=$(echo "$mountexpr" \| awk 'BEGIN{FS=":"}{print $1;}')
	external=$(echo "$mountexpr" \| awk 'BEGIN{FS=":"}{print $2;}')
	internal=$(echo "$mountexpr" \| awk 'BEGIN{FS=":"}{print $3;}' \| sed -e 's#^/##' -e 's#//#/#g')

	case "$mount_type" in
	ro\|rw)
	:
	;;
	*)
	echo ERROR: "Wrong mount type (should be 'ro' or 'rw') in: ${mountexpr}" >&2
	exit 1
	;;
	esac

	if ! [ -d "$external" ] ; then
	echo ERROR: "Directory for mounting does not exist: ${external}" >&2
	exit 1
	fi

	if echo "$internal" \| grep -q '^/*$' ; then
	echo ERROR: "Unacceptable internal path: ${internal}" >&2
	exit 1
	fi
	done
	}

	do_external_mounts()
	{
	echo INFO: "Bind mounting of external mounts..." >&2
	echo "$EXTERNAL_MOUNTS" \| sed '/^[[:space:]]*$/d' \| while read -r mountexpr ; do
	mount_type=$(echo "$mountexpr" \| awk 'BEGIN{FS=":"}{print $1;}')
	external=$(echo "$mountexpr" \| awk 'BEGIN{FS=":"}{print $2;}')
	internal=$(echo "$mountexpr" \| awk 'BEGIN{FS=":"}{print $3;}' \| sed -e 's#^/##' -e 's#//#/#g')

	if is_mounted "${CHROOT_DIR}/${internal}" ; then
	echo ERROR: "Mountpoint is already mounted: ${CHROOT_DIR}/${internal}" >&2
	echo ERROR: "Fix the issue - cannot proceed" >&2
	exit 1
	fi

	if ! mkdir -p "${CHROOT_DIR}/${internal}" ; then
	echo ERROR: "Cannot create mountpoint: ${CHROOT_DIR}/${internal}" >&2
	exit 1
	fi

	if ! mount --make-rprivate -o bind,${mount_type} "$external" "${CHROOT_DIR}/${internal}" ; then
	echo ERROR: "Failed to mount: ${external} -> ${internal}" >&2
	exit 1
	else
	echo INFO: "Mount: ${external} -> ${internal}" >&2
	fi
	done
	}

	# arg: <mountpoint>
	umount_retry()
	{
	mountpoint=$(echo "$1" \| sed 's#//*#/#g')
	timeout=${UMOUNT_TIMEOUT}

	umount "$mountpoint" 2>/dev/null
	while is_mounted "$mountpoint" && [ $timeout -gt 0 ] ; do
	umount "$mountpoint" 2>/dev/null
	sleep 1
	timeout=$(( timeout - 1 ))
	done

	if ! is_mounted "$mountpoint" ; then
	return 0
	fi

	return 1
	}

	undo_external_mounts()
	{
	echo INFO: "Umount external mount points..." >&2
	echo "$EXTERNAL_MOUNTS" \| tac \| sed '/^[[:space:]]*$/d' \| while read -r mountexpr ; do
	mount_type=$(echo "$mountexpr" \| awk 'BEGIN{FS=":"}{print $1;}')
	external=$(echo "$mountexpr" \| awk 'BEGIN{FS=":"}{print $2;}')
	internal=$(echo "$mountexpr" \| awk 'BEGIN{FS=":"}{print $3;}' \| sed -e 's#^/##' -e 's#//#/#g')
	if umount_retry "${CHROOT_DIR}/${internal}" ; then
	echo INFO: "Unmounted: ${CHROOT_DIR}/${internal}" >&2
	else
	echo ERROR: "Failed to umount: ${CHROOT_DIR}/${internal}" >&2
	fi
	done
	}

	install_wrapper()
	{
	cat > "$CHROOT_DIR"/usr/local/bin/fakeshell.sh <<EOF
	#!/bin/sh

	PATH=/usr/local/sbin:/usr/local/bin:/usr/sbin:/usr/bin:/sbin:/bin
	export PATH

	gid_tty=\$(getent group \| sed -n '/^tty:/p' \| cut -d: -f 3)

	mount -t proc proc /proc
	mount -t sysfs none /sys
	mount -t tmpfs none /dev

	mkdir -p /dev/shm
	mkdir -p /dev/pts
	mount -t devpts -o gid=\${gid_tty},mode=620 none /dev/pts

	[ -e /dev/full ] \|\| mknod -m 666 /dev/full c 1 7
	[ -e /dev/ptmx ] \|\| mknod -m 666 /dev/ptmx c 5 2
	[ -e /dev/random ] \|\| mknod -m 644 /dev/random c 1 8
	[ -e /dev/urandom ] \|\| mknod -m 644 /dev/urandom c 1 9
	[ -e /dev/zero ] \|\| mknod -m 666 /dev/zero c 1 5
	[ -e /dev/tty ] \|\| mknod -m 666 /dev/tty c 5 0
	[ -e /dev/console ] \|\| mknod -m 622 /dev/console c 5 1
	[ -e /dev/null ] \|\| mknod -m 666 /dev/null c 1 3

	chown root:tty /dev/console
	chown root:tty /dev/ptmx
	chown root:tty /dev/tty

	mkdir -p "\$1" \|\| exit 1
	cd "\$1" \|\| exit 1
	shift

	exec "\$@"

	EOF
	chmod +x "$CHROOT_DIR"/usr/local/bin/fakeshell.sh
	}

	on_exit()
	{
	set +e
	echo

	if [ -n "$OVERLAY_MOUNT" ] ; then
	undo_external_mounts
	fi
	cleanup
	}


	#
	# parse arguments
	#

	state=nil
	action=nil
	EXTERNAL_MOUNTS=''
	CHROOT_WORKDIR=''
	CHROOT_METADIR=''
	CHROOT_DIR=''
	COMMAND=''
	while [ -n "$1" ] ; do
	case "$state" in
	nil)
	case "$1" in
	''\|-h\|--help\|help)
	help
	exit 0
	;;
	--mount)
	EXTERNAL_MOUNTS=$(printf "%s\n%s\n" "$EXTERNAL_MOUNTS" "${2}")
	state=next
	;;
	--workdir)
	if [ -z "$CHROOT_WORKDIR" ] ; then
	CHROOT_WORKDIR="$2"
	state=next
	else
	echo ERROR: "Multiple working directory argument" >&2
	help >&2
	exit 1
	fi
	;;
	execute)
	action=execute
	state=execute
	;;
	*)
	echo ERROR: "Bad usage" >&2
	help >&2
	exit 1
	;;
	esac
	;;
	next)
	state=nil
	;;
	execute)
	CHROOT_METADIR="$1"
	shift
	break
	;;
	esac
	shift
	done


	case "$action" in
	''\|nil)
	echo ERROR: "Nothing to do - missing command" >&2
	help >&2
	exit 1
	;;
	execute)
	# firstly do sanity checking ...

	if [ -z "$CHROOT_METADIR" ] ; then
	echo ERROR: "Missing argument" >&2
	help >&2
	exit 1
	fi

	# making sure that CHROOT_METADIR is absolute path
	CHROOT_METADIR=$(readlink -f "$CHROOT_METADIR")

	if ! [ -d "$CHROOT_METADIR"/chroot ] ; then
	echo ERROR: "Filepath does not exist: ${CHROOT_METADIR}/chroot" >&2
	exit 1
	fi

	# check external mounts if there are any
	check_external_mounts

	# check workdir
	if [ -n "$CHROOT_WORKDIR" ] ; then
	CHROOT_WORKDIR=$(echo "$CHROOT_WORKDIR" \| sed -e 's#^/##' -e 's#//#/#g')
	fi

	# we must be root
	if [ "$(id -u)" -ne 0 ] ; then
	echo ERROR: "Need to be root and you are not: $(id -nu)" >&2
	exit 1
	fi

	if ! which unshare >/dev/null 2>/dev/null ; then
	echo ERROR: "'unshare' system command is missing - ABORT" >&2
	echo INFO: "Try to install 'util-linux' package" >&2
	exit 1
	fi

	# ... sanity checking done

	# setup paths
	lowerdir="$CHROOT_METADIR"/chroot
	upperdir="$CHROOT_METADIR"/.overlay
	workdir="$CHROOT_METADIR"/.workdir
	overlay="$CHROOT_METADIR"/.merged

	# set trap
	trap on_exit QUIT TERM EXIT

	# mount overlay
	OVERLAY_MOUNT=''
	if do_overlay_mount ; then
	# overlay chroot
	OVERLAY_MOUNT=yes
	else
	# non overlay mount
	OVERLAY_MOUNT=no
	fi

	# do the user-specific mounts
	do_external_mounts

	# I need this wrapper to do some setup inside the chroot...
	install_wrapper

	# execute chroot
	# copy resolv.conf
	cp -a /etc/resolv.conf "$CHROOT_DIR"/etc/resolv.conf

	if [ -n "$1" ] ; then
	:
	else
	set -- /bin/sh -l
	fi
	unshare -mfpi --propagation private \
	chroot "$CHROOT_DIR" /usr/local/bin/fakeshell.sh "${CHROOT_WORKDIR:-/}" "$@"
	;;
	esac

	exit 0