enter_chroot.sh - mirrors/cros/chromiumos/platform/crosutils - Git at Google

 #!/bin/bash

 # Copyright (c) 2011 The Chromium OS Authors. All rights reserved.
 # Use of this source code is governed by a BSD-style license that can be
 # found in the LICENSE file.

 # Script to enter the chroot environment

 # --- BEGIN COMMON.SH BOILERPLATE ---
 # Load common CrOS utilities.  Inside the chroot this file is installed in
 # /usr/lib/crosutils.  Outside the chroot we find it relative to the script's
 # location.
 find_common_sh() {
   local common_paths=(/usr/lib/crosutils $(dirname "$(readlink -f "$0")"))
   local path

   SCRIPT_ROOT=
   for path in "${common_paths[@]}"; do
     if [ -r "${path}/common.sh" ]; then
       SCRIPT_ROOT=${path}
       break
     fi
   done
 }

 find_common_sh
 . "${SCRIPT_ROOT}/common.sh" || { echo "Unable to load common.sh"; exit 1; }
 # --- END COMMON.SH BOILERPLATE ---

 # Script must be run outside the chroot and as a regular user.
 assert_outside_chroot
 assert_not_root_user

 # Define command line flags
 # See http://code.google.com/p/shflags/wiki/Documentation10x
 DEFINE_string chroot "$DEFAULT_CHROOT_DIR" \
   "The destination dir for the chroot environment." "d"
 DEFINE_string trunk "$GCLIENT_ROOT" \
   "The source trunk to bind mount within the chroot." "s"
 DEFINE_string build_number "" \
   "The build-bot build number (when called by buildbot only)." "b"
 DEFINE_string chrome_root "" \
   "The root of your chrome browser source. Should contain a 'src' subdir."
 DEFINE_string chrome_root_mount "/home/$USER/chrome_root" \
   "The mount point of the chrome broswer source in the chroot."

 DEFINE_boolean official_build $FLAGS_FALSE \
   "Set CHROMEOS_OFFICIAL=1 for release builds."
 DEFINE_boolean mount $FLAGS_FALSE "Only set up mounts."
 DEFINE_boolean unmount $FLAGS_FALSE "Only tear down mounts."
 DEFINE_boolean ssh_agent $FLAGS_TRUE "Import ssh agent."
 DEFINE_boolean verbose $FLAGS_FALSE "Print out actions taken"

 # More useful help
 FLAGS_HELP="USAGE: $0 [flags] [VAR=value] [-- command [arg1] [arg2] ...]

 One or more VAR=value pairs can be specified to export variables into
 the chroot environment.  For example:

    $0 FOO=bar BAZ=bel

 If [-- command] is present, runs the command inside the chroot,
 after changing directory to /$USER/trunk/src/scripts.  Note that neither
 the command nor args should include single quotes.  For example:

     $0 -- ./build_platform_packages.sh

 Otherwise, provides an interactive shell.
 "

 # Version of info from common.sh that only echos if --verbose is set.
 function debug {
   if [ $FLAGS_verbose -eq $FLAGS_TRUE ]; then
     info "$*"
   fi
 }

 # Parse command line flags
 FLAGS "$@" || exit 1
 eval set -- "${FLAGS_ARGV}"

 if [ $FLAGS_official_build -eq $FLAGS_TRUE ]; then
    CHROMEOS_OFFICIAL=1
 fi

 # Only now can we die on error.  shflags functions leak non-zero error codes,
 # so will die prematurely if 'set -e' is specified before now.
 # TODO: replace shflags with something less error-prone, or contribute a fix.
 set -e

 INNER_CHROME_ROOT=$FLAGS_chrome_root_mount  # inside chroot
 CHROME_ROOT_CONFIG="/var/cache/chrome_root"  # inside chroot
 INNER_DEPOT_TOOLS_ROOT="/home/$USER/depot_tools"  # inside chroot
 FUSE_DEVICE="/dev/fuse"
 AUTOMOUNT_PREF="/apps/nautilus/preferences/media_automount"
 SAVED_AUTOMOUNT_PREF_FILE="/tmp/.automount_pref"

 sudo chmod 0777 "$FLAGS_chroot/var/lock"

 LOCKFILE="$FLAGS_chroot/var/lock/enter_chroot"
 SYNCERPIDFILE="${FLAGS_chroot}/var/tmp/enter_chroot_sync.pid"


 function ensure_mounted {
   # If necessary, mount $source in the host FS at $target inside the
   # chroot directory with $mount_args.
   local source="$1"
   local mount_args="$2"
   local target="$3"

   local mounted_path="$(readlink -f "${FLAGS_chroot}/$target")"

   if [ -z "$(mount | grep -F "on ${mounted_path} ")" ]; then
     # Attempt to make the mountpoint as the user.  This depends on the
     # fact that all mountpoints that should be owned by root are
     # already present.
     mkdir -p "${mounted_path}"

     # NB:  mount_args deliberately left unquoted
     debug mount ${mount_args} "${source}" "${mounted_path}"
     sudo -- mount ${mount_args} "${source}" "${mounted_path}" || \
       die "Could not mount ${source} on ${mounted_path}"
   fi
 }

 function env_sync_proc {
   # This function runs and performs periodic updates to the chroot env, if
   # necessary.

   local poll_interval=10
   local sync_files="etc/resolv.conf etc/hosts"

   # Make sure the synced files are writable by normal user, so that we
   # don't have to sudo inside the loop.
   for file in ${sync_files}; do
     sudo chown ${USER} ${FLAGS_chroot}/${file} 1>&2
   done

   # Drop stdin, stderr, stdout, and chroot lock.
   # This is needed for properly daemonizing the process.
   exec 0>&- 1>&- 2>&- 200>&-

   while true; do
     # Sync files
     for file in ${sync_files}; do
       if ! cmp /${file} ${FLAGS_chroot}/${file} &> /dev/null; then
         cp -f /${file} ${FLAGS_chroot}/${file}
       fi
     done

     sleep ${poll_interval}
   done
 }

 function copy_ssh_config {
   # Copy user .ssh/config into the chroot filtering out strings not supported
   # by the chroot ssh. The chroot .ssh directory is passed in as the first
   # parameter.

   # ssh options to filter out. The entire strings containing these substrings
   # will be deleted before copying.
   local bad_options=(
     'UseProxyIf='
     'GSSAPIAuthentication no'
   )
   local sshc="${HOME}/.ssh/config"
   local chroot_ssh_dir="${1}"
   local filter
   local option

   if [ ! -f "${sshc}" ]; then
     return # Nothing to copy.
   fi

   for option in "${bad_options[@]}"
   do
     if [ -z "${filter}" ]; then
       filter="${option}"
     else
       filter+="\\|${option}"
     fi
   done

   sed "/^.*\(${filter}\).*$/d" "${sshc}" > "${chroot_ssh_dir}/config"
 }

 function setup_env {
   # Validate sudo timestamp before entering the critical section so that we
   # don't stall for a password while we have the lockfile.
   # Don't use sudo -v since that has issues on machines w/ no password.
   sudo echo "" > /dev/null

   (
     flock 200
     echo $$ >> "$LOCKFILE"

     # If there isn't a syncer daemon started already, start one.  The
     # daemon is considered to not be started under the following
     # conditions:
     #
     #   o There is no PID file
     #
     #   o The PID file is 0 bytes in size, which might be a partial
     #     manifestation of chromium-os:17680.  This situation will not
     #     occur anymore, but you might have a chroot which was already
     #     affected.
     #
     #   o The /proc node for the process named by the PID file does
     #     not exist.
     #
     #     Note: This does not address PID recycling.  While
     #           increasingly unlikely, it is possible for the PID in
     #           the PID file to refer to a running process that is not
     #           the syncer process.  Since the PID file is now
     #           removed, I think it is only possible for this to occur
     #           if your system crashes and the PID file exists after
     #           restart.
     #
     # The daemon is killed by the enter_chroot that exits last.
     if [ -f "${SYNCERPIDFILE}" ] && [ ! -s "${SYNCERPIDFILE}" ] ; then
         info "You may have suffered from chromium-os:17680 and";
         info "could have stray 'enter_chroot.sh' processes running.";
         info "You must manually kill any such stray processes.";
         info "Exit all chroot shells; remaining 'enter_chroot.sh'";
         info "processes are probably stray.";
         sudo rm -f "${SYNCERPIDFILE}";
     fi;
     if ! [ -f "${SYNCERPIDFILE}" ] || \
        ! [ -d /proc/$(cat "${SYNCERPIDFILE}") ]; then
       debug "Starting sync process"
       env_sync_proc &
       echo $! > "${SYNCERPIDFILE}"
       disown $!
     fi

     debug "Mounting chroot environment."
     ensure_mounted none "-t proc" /proc
     ensure_mounted none "-t sysfs" /sys
     ensure_mounted /dev "--bind" /dev
     ensure_mounted none "-t devpts" /dev/pts
     ensure_mounted "${FLAGS_trunk}" "--bind" "${CHROOT_TRUNK_DIR}"

     if [ $FLAGS_ssh_agent -eq $FLAGS_TRUE ]; then
       TARGET_DIR="$(readlink -f "${FLAGS_chroot}/home/${USER}/.ssh")"
       if [ -n "${SSH_AUTH_SOCK}" -a -d "${HOME}/.ssh" ]; then
         mkdir -p "${TARGET_DIR}"
         cp -r "${HOME}/.ssh/known_hosts" "${TARGET_DIR}"
         cp -r ${HOME}/.ssh/*.pub "${TARGET_DIR}"
         copy_ssh_config "${TARGET_DIR}"
         ASOCK="$(dirname "${SSH_AUTH_SOCK}")"
         ensure_mounted "${ASOCK}" "--bind" "${ASOCK}"
       fi
     fi

     MOUNTED_PATH="$(readlink -f "${FLAGS_chroot}${INNER_CHROME_ROOT}")"
     if [ -z "$(mount | grep -F "on $MOUNTED_PATH ")" ]; then
       ! CHROME_ROOT="$(readlink -f "$FLAGS_chrome_root")"
       if [ -z "$CHROME_ROOT" ]; then
         ! CHROME_ROOT="$(cat "${FLAGS_chroot}${CHROME_ROOT_CONFIG}" \
           2>/dev/null)"
         CHROME_ROOT_AUTO=1
       fi
       if [[ ( -n "$CHROME_ROOT" ) ]]; then
         if [[ ( ! -d "${CHROME_ROOT}/src" ) ]]; then
           error "Not mounting chrome source"
           sudo rm -f "${FLAGS_chroot}${CHROME_ROOT_CONFIG}"
           if [[ ! "$CHROME_ROOT_AUTO" ]]; then
             exit 1
           fi
         else
           debug "Mounting chrome source at: $INNER_CHROME_ROOT"
           sudo bash -c "echo '$CHROME_ROOT' > \
             '${FLAGS_chroot}${CHROME_ROOT_CONFIG}'"
           mkdir -p "$MOUNTED_PATH"
           sudo mount --bind "$CHROME_ROOT" "$MOUNTED_PATH" || \
             die "Could not mount $MOUNTED_PATH"
         fi
       fi
     fi

     MOUNTED_PATH="$(readlink -f "${FLAGS_chroot}${INNER_DEPOT_TOOLS_ROOT}")"
     if [ -z "$(mount | grep -F "on $MOUNTED_PATH ")" ]; then
       if [ $(which gclient 2>/dev/null) ]; then
         debug "Mounting depot_tools"
         DEPOT_TOOLS=$(dirname "$(which gclient)")
         mkdir -p "$MOUNTED_PATH"
         if ! sudo mount --bind "$DEPOT_TOOLS" "$MOUNTED_PATH"; then
           warn "depot_tools failed to mount; perhaps it's on NFS?"
           warn "This may impact chromium build."
         fi
       fi
     fi

     # Install fuse module.
     if [ -c "${FUSE_DEVICE}" ]; then
       sudo modprobe fuse 2> /dev/null ||\
         warn "-- Note: modprobe fuse failed.  gmergefs will not work"
     fi

     # Turn off automounting of external media when we enter the
     # chroot; thus we don't have to worry about being able to unmount
     # from inside.
     if [ $(which gconftool-2 2>/dev/null) ]; then
       gconftool-2 -g ${AUTOMOUNT_PREF} > \
         "${FLAGS_chroot}${SAVED_AUTOMOUNT_PREF_FILE}"
       if [ $(gconftool-2 -s --type=boolean ${AUTOMOUNT_PREF} false) ]; then
         warn "-- Note: USB sticks may be automounted by your host OS."
         warn "-- Note: If you plan to burn bootable media, you may need to"
         warn "-- Note: unmount these devices manually, or run image_to_usb.sh"
         warn "-- Note: outside the chroot."
       fi
     fi

     if [ -d "$HOME/.subversion" ]; then
       TARGET="/home/${USER}/.subversion"
       mkdir -p "${FLAGS_chroot}${TARGET}"
       ensure_mounted "${HOME}/.subversion" "--bind" "${TARGET}"
     fi

     # Configure committer username and email in chroot .gitconfig
     git config -f ${FLAGS_chroot}/home/${USER}/.gitconfig --replace-all \
       user.name "$(cd /tmp; git var GIT_COMMITTER_IDENT | \
       sed -e 's/ *<.*//')" || true
     git config -f ${FLAGS_chroot}/home/${USER}/.gitconfig --replace-all \
       user.email "$(cd /tmp; git var GIT_COMMITTER_IDENT | \
         sed -e 's/.*<\([^>]*\)>.*/\1/')" || true

     # Fix permissions on shared memory to allow non-root users access to POSIX
     # semaphores.
     sudo chmod -R 777 "${FLAGS_chroot}/dev/shm"
   ) 200>>"$LOCKFILE" || die "setup_env failed"
 }

 function teardown_env {
   # Validate sudo timestamp before entering the critical section so that we
   # don't stall for a password while we have the lockfile.
   # Don't use sudo -v since that has issues on machines w/ no password.
   sudo echo "" > /dev/null

   # Only teardown if we're the last enter_chroot to die
   (
     flock 200

     # check each pid in $LOCKFILE to see if it's died unexpectedly
     TMP_LOCKFILE="$LOCKFILE.tmp"

     echo -n > "$TMP_LOCKFILE"  # Erase/reset temp file
     cat "$LOCKFILE" | while read PID; do
       if [ "$PID" = "$$" ]; then
         # ourself, leave PROC_NAME empty
         PROC_NAME=""
       else
         PROC_NAME=$(ps --pid $PID -o comm=)
       fi

       if [ ! -z "$PROC_NAME" ]; then
         # All good, keep going
         echo "$PID" >> "$TMP_LOCKFILE"
       fi
     done
     # Remove any dups from lock file while installing new one
     sort -n "$TMP_LOCKFILE" | uniq > "$LOCKFILE"

     if [ $(which gconftool-2 2>/dev/null) ]; then
       SAVED_PREF=$(cat "${FLAGS_chroot}${SAVED_AUTOMOUNT_PREF_FILE}")
       gconftool-2 -s --type=boolean ${AUTOMOUNT_PREF} ${SAVED_PREF} || \
         warn "could not re-set your automount preference."
     fi

     if [ -s "$LOCKFILE" ]; then
       debug "At least one other pid is running in the chroot, so not"
       debug "tearing down env."
     else
       debug "Stopping syncer process"
       # If another process entering the chroot is blocked on this
       # flock in setup_env(), it can be a race condition.
       #
       # When this locked region is exited, the setup_env() flock can
       # be entered before the script can exit and the /proc entry for
       # the PID is removed.  The newly-created chroot will not end up
       # with a syncer process.  To avoid that situation, remove the
       # syncer PID file.
       #
       # The syncer PID file should also be removed because the kernel
       # will reuse PIDs.  It's possible that the PID in the syncer PID
       # has been reused by another process; make sure we don't skip
       # starting the syncer process when this occurs by deleting the
       # PID file.
       kill $(cat "${SYNCERPIDFILE}") && \
           sudo rm -f "${SYNCERPIDFILE}" || \
           debug "Unable to clean up syncer process.";

       MOUNTED_PATH=$(readlink -f "$FLAGS_chroot")
       debug "Unmounting chroot environment."
       # sort the list of mounts in reverse order, to ensure umount of
       # cascading mounts in proper order
       for i in \
         $(mount | grep -F "on $MOUNTED_PATH/" | sort -r | awk '{print $3}'); do
         safe_umount "$i"
       done
     fi
   ) 200>>"$LOCKFILE" || die "teardown_env failed"
 }

 if [ $FLAGS_mount -eq $FLAGS_TRUE ]; then
   setup_env
   info "Make sure you run"
   info "    $0 --unmount"
   info "before deleting $FLAGS_chroot"
   info "or you'll end up deleting $FLAGS_trunk too!"
   exit 0
 fi

 if [ $FLAGS_unmount -eq $FLAGS_TRUE ]; then
   teardown_env
   exit 0
 fi

 # Make sure we unmount before exiting
 trap teardown_env EXIT
 setup_env

 CHROOT_PASSTHRU="BUILDBOT_BUILD=$FLAGS_build_number CHROMEOS_OFFICIAL=$CHROMEOS_OFFICIAL"
 CHROOT_PASSTHRU="${CHROOT_PASSTHRU} \
 CHROMEOS_RELEASE_APPID=${CHROMEOS_RELEASE_APPID:-"{DEV-BUILD}"}"

 # Set CHROMEOS_VERSION_TRACK, CHROMEOS_VERSION_AUSERVER,
 # CHROMEOS_VERSION_DEVSERVER as environment variables to override the default
 # assumptions (local AU server). These are used in cros_set_lsb_release, and
 # are used by external Chromium OS builders.
 CHROOT_PASSTHRU="${CHROOT_PASSTHRU} \
 CHROMEOS_VERSION_TRACK=${CHROMEOS_VERSION_TRACK} \
 CHROMEOS_VERSION_AUSERVER=${CHROMEOS_VERSION_AUSERVER} \
 CHROMEOS_VERSION_DEVSERVER=${CHROMEOS_VERSION_DEVSERVER}"

 # Pass proxy variables into the environment.
 for type in http_proxy ftp_proxy all_proxy GIT_PROXY_COMMAND GIT_SSH; do
    eval value=\$${type}
    if [ -n "${value}" ]; then
       CHROOT_PASSTHRU="${CHROOT_PASSTHRU} ${type}=${value}"
    fi
 done

 # Run command or interactive shell.  Also include the non-chrooted path to
 # the source trunk for scripts that may need to print it (e.g.
 # build_image.sh).
 sudo -- chroot "$FLAGS_chroot" sudo -i -u $USER $CHROOT_PASSTHRU \
   EXTERNAL_TRUNK_PATH="${FLAGS_trunk}" LANG=C SSH_AGENT_PID="${SSH_AGENT_PID}" \
   SSH_AUTH_SOCK="${SSH_AUTH_SOCK}" "$@"

 # Remove trap and explicitly unmount
 trap - EXIT
 teardown_env
	#!/bin/bash

	# Copyright (c) 2011 The Chromium OS Authors. All rights reserved.
	# Use of this source code is governed by a BSD-style license that can be
	# found in the LICENSE file.

	# Script to enter the chroot environment

	# --- BEGIN COMMON.SH BOILERPLATE ---
	# Load common CrOS utilities. Inside the chroot this file is installed in
	# /usr/lib/crosutils. Outside the chroot we find it relative to the script's
	# location.
	find_common_sh() {
	local common_paths=(/usr/lib/crosutils $(dirname "$(readlink -f "$0")"))
	local path

	SCRIPT_ROOT=
	for path in "${common_paths[@]}"; do
	if [ -r "${path}/common.sh" ]; then
	SCRIPT_ROOT=${path}
	break
	fi
	done
	}

	find_common_sh
	. "${SCRIPT_ROOT}/common.sh" \|\| { echo "Unable to load common.sh"; exit 1; }
	# --- END COMMON.SH BOILERPLATE ---

	# Script must be run outside the chroot and as a regular user.
	assert_outside_chroot
	assert_not_root_user

	# Define command line flags
	# See http://code.google.com/p/shflags/wiki/Documentation10x
	DEFINE_string chroot "$DEFAULT_CHROOT_DIR" \
	"The destination dir for the chroot environment." "d"
	DEFINE_string trunk "$GCLIENT_ROOT" \
	"The source trunk to bind mount within the chroot." "s"
	DEFINE_string build_number "" \
	"The build-bot build number (when called by buildbot only)." "b"
	DEFINE_string chrome_root "" \
	"The root of your chrome browser source. Should contain a 'src' subdir."
	DEFINE_string chrome_root_mount "/home/$USER/chrome_root" \
	"The mount point of the chrome broswer source in the chroot."

	DEFINE_boolean official_build $FLAGS_FALSE \
	"Set CHROMEOS_OFFICIAL=1 for release builds."
	DEFINE_boolean mount $FLAGS_FALSE "Only set up mounts."
	DEFINE_boolean unmount $FLAGS_FALSE "Only tear down mounts."
	DEFINE_boolean ssh_agent $FLAGS_TRUE "Import ssh agent."
	DEFINE_boolean verbose $FLAGS_FALSE "Print out actions taken"

	# More useful help
	FLAGS_HELP="USAGE: $0 [flags] [VAR=value] [-- command [arg1] [arg2] ...]

	One or more VAR=value pairs can be specified to export variables into
	the chroot environment. For example:

	$0 FOO=bar BAZ=bel

	If [-- command] is present, runs the command inside the chroot,
	after changing directory to /$USER/trunk/src/scripts. Note that neither
	the command nor args should include single quotes. For example:

	$0 -- ./build_platform_packages.sh

	Otherwise, provides an interactive shell.
	"

	# Version of info from common.sh that only echos if --verbose is set.
	function debug {
	if [ $FLAGS_verbose -eq $FLAGS_TRUE ]; then
	info "$*"
	fi
	}

	# Parse command line flags
	FLAGS "$@" \|\| exit 1
	eval set -- "${FLAGS_ARGV}"

	if [ $FLAGS_official_build -eq $FLAGS_TRUE ]; then
	CHROMEOS_OFFICIAL=1
	fi

	# Only now can we die on error. shflags functions leak non-zero error codes,
	# so will die prematurely if 'set -e' is specified before now.
	# TODO: replace shflags with something less error-prone, or contribute a fix.
	set -e

	INNER_CHROME_ROOT=$FLAGS_chrome_root_mount # inside chroot
	CHROME_ROOT_CONFIG="/var/cache/chrome_root" # inside chroot
	INNER_DEPOT_TOOLS_ROOT="/home/$USER/depot_tools" # inside chroot
	FUSE_DEVICE="/dev/fuse"
	AUTOMOUNT_PREF="/apps/nautilus/preferences/media_automount"
	SAVED_AUTOMOUNT_PREF_FILE="/tmp/.automount_pref"

	sudo chmod 0777 "$FLAGS_chroot/var/lock"

	LOCKFILE="$FLAGS_chroot/var/lock/enter_chroot"
	SYNCERPIDFILE="${FLAGS_chroot}/var/tmp/enter_chroot_sync.pid"


	function ensure_mounted {
	# If necessary, mount $source in the host FS at $target inside the
	# chroot directory with $mount_args.
	local source="$1"
	local mount_args="$2"
	local target="$3"

	local mounted_path="$(readlink -f "${FLAGS_chroot}/$target")"

	if [ -z "$(mount \| grep -F "on ${mounted_path} ")" ]; then
	# Attempt to make the mountpoint as the user. This depends on the
	# fact that all mountpoints that should be owned by root are
	# already present.
	mkdir -p "${mounted_path}"

	# NB: mount_args deliberately left unquoted
	debug mount ${mount_args} "${source}" "${mounted_path}"
	sudo -- mount ${mount_args} "${source}" "${mounted_path}" \|\| \
	die "Could not mount ${source} on ${mounted_path}"
	fi
	}

	function env_sync_proc {
	# This function runs and performs periodic updates to the chroot env, if
	# necessary.

	local poll_interval=10
	local sync_files="etc/resolv.conf etc/hosts"

	# Make sure the synced files are writable by normal user, so that we
	# don't have to sudo inside the loop.
	for file in ${sync_files}; do
	sudo chown ${USER} ${FLAGS_chroot}/${file} 1>&2
	done

	# Drop stdin, stderr, stdout, and chroot lock.
	# This is needed for properly daemonizing the process.
	exec 0>&- 1>&- 2>&- 200>&-

	while true; do
	# Sync files
	for file in ${sync_files}; do
	if ! cmp /${file} ${FLAGS_chroot}/${file} &> /dev/null; then
	cp -f /${file} ${FLAGS_chroot}/${file}
	fi
	done

	sleep ${poll_interval}
	done
	}

	function copy_ssh_config {
	# Copy user .ssh/config into the chroot filtering out strings not supported
	# by the chroot ssh. The chroot .ssh directory is passed in as the first
	# parameter.

	# ssh options to filter out. The entire strings containing these substrings
	# will be deleted before copying.
	local bad_options=(
	'UseProxyIf='
	'GSSAPIAuthentication no'
	)
	local sshc="${HOME}/.ssh/config"
	local chroot_ssh_dir="${1}"
	local filter
	local option

	if [ ! -f "${sshc}" ]; then
	return # Nothing to copy.
	fi

	for option in "${bad_options[@]}"
	do
	if [ -z "${filter}" ]; then
	filter="${option}"
	else
	filter+="\\\|${option}"
	fi
	done

	sed "/^.\(${filter}\).$/d" "${sshc}" > "${chroot_ssh_dir}/config"
	}

	function setup_env {
	# Validate sudo timestamp before entering the critical section so that we
	# don't stall for a password while we have the lockfile.
	# Don't use sudo -v since that has issues on machines w/ no password.
	sudo echo "" > /dev/null

	(
	flock 200
	echo $$ >> "$LOCKFILE"

	# If there isn't a syncer daemon started already, start one. The
	# daemon is considered to not be started under the following
	# conditions:
	#
	# o There is no PID file
	#
	# o The PID file is 0 bytes in size, which might be a partial
	# manifestation of chromium-os:17680. This situation will not
	# occur anymore, but you might have a chroot which was already
	# affected.
	#
	# o The /proc node for the process named by the PID file does
	# not exist.
	#
	# Note: This does not address PID recycling. While
	# increasingly unlikely, it is possible for the PID in
	# the PID file to refer to a running process that is not
	# the syncer process. Since the PID file is now
	# removed, I think it is only possible for this to occur
	# if your system crashes and the PID file exists after
	# restart.
	#
	# The daemon is killed by the enter_chroot that exits last.
	if [ -f "${SYNCERPIDFILE}" ] && [ ! -s "${SYNCERPIDFILE}" ] ; then
	info "You may have suffered from chromium-os:17680 and";
	info "could have stray 'enter_chroot.sh' processes running.";
	info "You must manually kill any such stray processes.";
	info "Exit all chroot shells; remaining 'enter_chroot.sh'";
	info "processes are probably stray.";
	sudo rm -f "${SYNCERPIDFILE}";
	fi;
	if ! [ -f "${SYNCERPIDFILE}" ] \|\| \
	! [ -d /proc/$(cat "${SYNCERPIDFILE}") ]; then
	debug "Starting sync process"
	env_sync_proc &
	echo $! > "${SYNCERPIDFILE}"
	disown $!
	fi

	debug "Mounting chroot environment."
	ensure_mounted none "-t proc" /proc
	ensure_mounted none "-t sysfs" /sys
	ensure_mounted /dev "--bind" /dev
	ensure_mounted none "-t devpts" /dev/pts
	ensure_mounted "${FLAGS_trunk}" "--bind" "${CHROOT_TRUNK_DIR}"

	if [ $FLAGS_ssh_agent -eq $FLAGS_TRUE ]; then
	TARGET_DIR="$(readlink -f "${FLAGS_chroot}/home/${USER}/.ssh")"
	if [ -n "${SSH_AUTH_SOCK}" -a -d "${HOME}/.ssh" ]; then
	mkdir -p "${TARGET_DIR}"
	cp -r "${HOME}/.ssh/known_hosts" "${TARGET_DIR}"
	cp -r ${HOME}/.ssh/*.pub "${TARGET_DIR}"
	copy_ssh_config "${TARGET_DIR}"
	ASOCK="$(dirname "${SSH_AUTH_SOCK}")"
	ensure_mounted "${ASOCK}" "--bind" "${ASOCK}"
	fi
	fi

	MOUNTED_PATH="$(readlink -f "${FLAGS_chroot}${INNER_CHROME_ROOT}")"
	if [ -z "$(mount \| grep -F "on $MOUNTED_PATH ")" ]; then
	! CHROME_ROOT="$(readlink -f "$FLAGS_chrome_root")"
	if [ -z "$CHROME_ROOT" ]; then
	! CHROME_ROOT="$(cat "${FLAGS_chroot}${CHROME_ROOT_CONFIG}" \
	2>/dev/null)"
	CHROME_ROOT_AUTO=1
	fi
	if [[ ( -n "$CHROME_ROOT" ) ]]; then
	if [[ ( ! -d "${CHROME_ROOT}/src" ) ]]; then
	error "Not mounting chrome source"
	sudo rm -f "${FLAGS_chroot}${CHROME_ROOT_CONFIG}"
	if [[ ! "$CHROME_ROOT_AUTO" ]]; then
	exit 1
	fi
	else
	debug "Mounting chrome source at: $INNER_CHROME_ROOT"
	sudo bash -c "echo '$CHROME_ROOT' > \
	'${FLAGS_chroot}${CHROME_ROOT_CONFIG}'"
	mkdir -p "$MOUNTED_PATH"
	sudo mount --bind "$CHROME_ROOT" "$MOUNTED_PATH" \|\| \
	die "Could not mount $MOUNTED_PATH"
	fi
	fi
	fi

	MOUNTED_PATH="$(readlink -f "${FLAGS_chroot}${INNER_DEPOT_TOOLS_ROOT}")"
	if [ -z "$(mount \| grep -F "on $MOUNTED_PATH ")" ]; then
	if [ $(which gclient 2>/dev/null) ]; then
	debug "Mounting depot_tools"
	DEPOT_TOOLS=$(dirname "$(which gclient)")
	mkdir -p "$MOUNTED_PATH"
	if ! sudo mount --bind "$DEPOT_TOOLS" "$MOUNTED_PATH"; then
	warn "depot_tools failed to mount; perhaps it's on NFS?"
	warn "This may impact chromium build."
	fi
	fi
	fi

	# Install fuse module.
	if [ -c "${FUSE_DEVICE}" ]; then
	sudo modprobe fuse 2> /dev/null \|\|\
	warn "-- Note: modprobe fuse failed. gmergefs will not work"
	fi

	# Turn off automounting of external media when we enter the
	# chroot; thus we don't have to worry about being able to unmount
	# from inside.
	if [ $(which gconftool-2 2>/dev/null) ]; then
	gconftool-2 -g ${AUTOMOUNT_PREF} > \
	"${FLAGS_chroot}${SAVED_AUTOMOUNT_PREF_FILE}"
	if [ $(gconftool-2 -s --type=boolean ${AUTOMOUNT_PREF} false) ]; then
	warn "-- Note: USB sticks may be automounted by your host OS."
	warn "-- Note: If you plan to burn bootable media, you may need to"
	warn "-- Note: unmount these devices manually, or run image_to_usb.sh"
	warn "-- Note: outside the chroot."
	fi
	fi

	if [ -d "$HOME/.subversion" ]; then
	TARGET="/home/${USER}/.subversion"
	mkdir -p "${FLAGS_chroot}${TARGET}"
	ensure_mounted "${HOME}/.subversion" "--bind" "${TARGET}"
	fi

	# Configure committer username and email in chroot .gitconfig
	git config -f ${FLAGS_chroot}/home/${USER}/.gitconfig --replace-all \
	user.name "$(cd /tmp; git var GIT_COMMITTER_IDENT \| \
	sed -e 's/ <.//')" \|\| true
	git config -f ${FLAGS_chroot}/home/${USER}/.gitconfig --replace-all \
	user.email "$(cd /tmp; git var GIT_COMMITTER_IDENT \| \
	sed -e 's/.<\([^>]\)>.*/\1/')" \|\| true

	# Fix permissions on shared memory to allow non-root users access to POSIX
	# semaphores.
	sudo chmod -R 777 "${FLAGS_chroot}/dev/shm"
	) 200>>"$LOCKFILE" \|\| die "setup_env failed"
	}

	function teardown_env {
	# Validate sudo timestamp before entering the critical section so that we
	# don't stall for a password while we have the lockfile.
	# Don't use sudo -v since that has issues on machines w/ no password.
	sudo echo "" > /dev/null

	# Only teardown if we're the last enter_chroot to die
	(
	flock 200

	# check each pid in $LOCKFILE to see if it's died unexpectedly
	TMP_LOCKFILE="$LOCKFILE.tmp"

	echo -n > "$TMP_LOCKFILE" # Erase/reset temp file
	cat "$LOCKFILE" \| while read PID; do
	if [ "$PID" = "$$" ]; then
	# ourself, leave PROC_NAME empty
	PROC_NAME=""
	else
	PROC_NAME=$(ps --pid $PID -o comm=)
	fi

	if [ ! -z "$PROC_NAME" ]; then
	# All good, keep going
	echo "$PID" >> "$TMP_LOCKFILE"
	fi
	done
	# Remove any dups from lock file while installing new one
	sort -n "$TMP_LOCKFILE" \| uniq > "$LOCKFILE"

	if [ $(which gconftool-2 2>/dev/null) ]; then
	SAVED_PREF=$(cat "${FLAGS_chroot}${SAVED_AUTOMOUNT_PREF_FILE}")
	gconftool-2 -s --type=boolean ${AUTOMOUNT_PREF} ${SAVED_PREF} \|\| \
	warn "could not re-set your automount preference."
	fi

	if [ -s "$LOCKFILE" ]; then
	debug "At least one other pid is running in the chroot, so not"
	debug "tearing down env."
	else
	debug "Stopping syncer process"
	# If another process entering the chroot is blocked on this
	# flock in setup_env(), it can be a race condition.
	#
	# When this locked region is exited, the setup_env() flock can
	# be entered before the script can exit and the /proc entry for
	# the PID is removed. The newly-created chroot will not end up
	# with a syncer process. To avoid that situation, remove the
	# syncer PID file.
	#
	# The syncer PID file should also be removed because the kernel
	# will reuse PIDs. It's possible that the PID in the syncer PID
	# has been reused by another process; make sure we don't skip
	# starting the syncer process when this occurs by deleting the
	# PID file.
	kill $(cat "${SYNCERPIDFILE}") && \
	sudo rm -f "${SYNCERPIDFILE}" \|\| \
	debug "Unable to clean up syncer process.";

	MOUNTED_PATH=$(readlink -f "$FLAGS_chroot")
	debug "Unmounting chroot environment."
	# sort the list of mounts in reverse order, to ensure umount of
	# cascading mounts in proper order
	for i in \
	$(mount \| grep -F "on $MOUNTED_PATH/" \| sort -r \| awk '{print $3}'); do
	safe_umount "$i"
	done
	fi
	) 200>>"$LOCKFILE" \|\| die "teardown_env failed"
	}

	if [ $FLAGS_mount -eq $FLAGS_TRUE ]; then
	setup_env
	info "Make sure you run"
	info " $0 --unmount"
	info "before deleting $FLAGS_chroot"
	info "or you'll end up deleting $FLAGS_trunk too!"
	exit 0
	fi

	if [ $FLAGS_unmount -eq $FLAGS_TRUE ]; then
	teardown_env
	exit 0
	fi

	# Make sure we unmount before exiting
	trap teardown_env EXIT
	setup_env

	CHROOT_PASSTHRU="BUILDBOT_BUILD=$FLAGS_build_number CHROMEOS_OFFICIAL=$CHROMEOS_OFFICIAL"
	CHROOT_PASSTHRU="${CHROOT_PASSTHRU} \
	CHROMEOS_RELEASE_APPID=${CHROMEOS_RELEASE_APPID:-"{DEV-BUILD}"}"

	# Set CHROMEOS_VERSION_TRACK, CHROMEOS_VERSION_AUSERVER,
	# CHROMEOS_VERSION_DEVSERVER as environment variables to override the default
	# assumptions (local AU server). These are used in cros_set_lsb_release, and
	# are used by external Chromium OS builders.
	CHROOT_PASSTHRU="${CHROOT_PASSTHRU} \
	CHROMEOS_VERSION_TRACK=${CHROMEOS_VERSION_TRACK} \
	CHROMEOS_VERSION_AUSERVER=${CHROMEOS_VERSION_AUSERVER} \
	CHROMEOS_VERSION_DEVSERVER=${CHROMEOS_VERSION_DEVSERVER}"

	# Pass proxy variables into the environment.
	for type in http_proxy ftp_proxy all_proxy GIT_PROXY_COMMAND GIT_SSH; do
	eval value=\$${type}
	if [ -n "${value}" ]; then
	CHROOT_PASSTHRU="${CHROOT_PASSTHRU} ${type}=${value}"
	fi
	done

	# Run command or interactive shell. Also include the non-chrooted path to
	# the source trunk for scripts that may need to print it (e.g.
	# build_image.sh).
	sudo -- chroot "$FLAGS_chroot" sudo -i -u $USER $CHROOT_PASSTHRU \
	EXTERNAL_TRUNK_PATH="${FLAGS_trunk}" LANG=C SSH_AGENT_PID="${SSH_AGENT_PID}" \
	SSH_AUTH_SOCK="${SSH_AUTH_SOCK}" "$@"

	# Remove trap and explicitly unmount
	trap - EXIT
	teardown_env