enter-chroot

#!/bin/sh
[ -z "$CONFIG" ] && CONFIG=./config
. "$CONFIG"
export H="$PWD"
ret=0

if [ -z "$R" ] ; then
	echo 'no R environment var set, your config is broken'
	exit 1
elif [ "$R" = / ] ; then
	echo "error: R=/ can't be used with this script, as it would make"
	echo "your host sys unusable after returning. (umounting /dev /proc...)"
	exit 1
fi

mkdir -p "$R"/src/tarballs
linux32=
if [ $(uname -m) = "x86_64" ] ; then
case "$A" in i?86)
	echo "trying to get into 32bit rootfs from 64bit host"
	[ -x ./linux32 ] && linux32=./linux32 || {
		$CC "$K"/linux32.c -static -s -Os -o ./linux32 && linux32=./linux32 || \
		echo -ne "warning: trying to chroot into i386 rootfs on x86_64" \
		         "kernel and building linux32 command failed\n"
	} ;;
esac
fi

uid="$(id -u)"
if [ -d /proc/self/ns ] ; then
	CHROOT=./super_chroot
	if [ ! -x "$CHROOT" ] ; then
		if ! $CC "$K"/super_chroot.c -static -s -Os -o "$CHROOT" 2>/dev/null ; then
			echo "error: failed to build super_chroot!"
			echo "try: musl-gcc KEEP/super_chroot.c -o super_chroot"
			echo "or: re-run ./enter-chroot as root."
			exit 1
		fi
	fi
	CHROOT="./super_chroot -b $C:./src/tarballs"
else
	if [ "$uid" != "0" ]; then
	    printf -- "need to be root. please enter password.\n"
	    su -c "$0"
	    exit $?
	fi

	# prevent from mounting twice
	if [ ! -d "$R"/dev/pts ] ; then
		mount --bind /dev "$R"/dev
		mount --bind /dev/pts "$R"/dev/pts
		mount --bind /dev/shm "$R"/dev/shm
		mount --bind /proc "$R"/proc
		mount --bind "$C" "$R"/src/tarballs
	fi

	CHROOT=chroot
fi

set_title() {
	[ "$TERM" != "linux" ] && [ "$TERM" != "vt100" ] && \
	printf "\033]2;%s\007" "$1"
}

if [ -n "$1" ]; then
    $linux32 $CHROOT "$R" /bin/env -i \
        HOME=/root PATH="/local/bin:/bin" TERM="$TERM" PS1='\u:\w$ ' \
	"$@"
	ret=$?
else
    set_title "SABOTAGE CHROOT $(basename $R)"

    echo "Entering chroot..."

    $linux32 $CHROOT "$R" /bin/env -i \
        HOME=/root TERM="$TERM" PS1='\u:\w$ ' \
        /bin/ash --login
	ret=$?

	#echo empty line so we get a proper prompt back
	echo
fi

tryumount() {
	dest="$1"
	if ! umount "$dest" 2>/dev/null; then
		echo "unmount failure ($dest), retrying in 1 sec..."
		sleep 1
		if ! umount -f "$dest" 2>/dev/null; then
		  echo "unmount -f failure ($dest), trying last resort umount -l"
		  umount -l "$dest"
		fi
	fi
}

if [ "$CHROOT" = "chroot" ] && [ -d "$R"/dev/pts ] ; then
	tryumount "$R"/src/tarballs
	tryumount "$R"/dev/pts
	tryumount "$R"/dev/shm
	tryumount "$R"/dev
	tryumount "$R"/proc
fi

exit $ret