enter-chroot

#!/bin/sh
#
# script to enter chroot
#

printhelp() {
	cat << EOF

Usage:
  $(basename $0) [command]
  
If 'command' is unspecified, ${0##*/} will launch /bin/sh.
  
EOF
}

msgerr() {
	echo "ERROR: $*"
}

unmount() {
	while true; do
		mountpoint -q $1 || break
		umount $1 2>/dev/null
	done
}
	
[ "$(id -u)" = "0" ] || {
	msgerr "$(basename $0) need root access!"
	printhelp
	exit 1
}

LFS="/mnt/lfs"

if [ -f ./config ]; then
	. ./config
fi

[ -d "$LFS" ] || {
	msgerr "Directory '$LFS' not exist!"
	printhelp
	exit 1
}

if [ ! "$1" ]; then
	CMD="/bin/sh"
else
	CMD=$*
fi

if [ -e /sys/firmware/efi/systab ]; then
	EFI_SYSTEM=1
fi

mount --bind /dev $LFS/dev
mount -t devpts devpts $LFS/dev/pts -o gid=5,mode=620
mount -t proc proc $LFS/proc
mount -t sysfs sysfs $LFS/sys
if [ -n "$EFI_SYSTEM" ]; then
	mount --bind /sys/firmware/efi/efivars $LFS/sys/firmware/efi/efivars
fi
mount -t tmpfs tmpfs $LFS/run

if [ -h $LFS/dev/shm ]; then
  mkdir -p $LFS/$(readlink $LFS/dev/shm)
fi

[ -f $LFS/etc/resolv.conf ] && {
	backupresolvconf=1
	mv $LFS/etc/resolv.conf $LFS/etc/resolv.conf.tmp
}
cp -L /etc/resolv.conf $LFS/etc

chroot "$LFS" /usr/bin/env -i \
HOME=/root \
TERM="$TERM" \
PS1='\u:\w\$ ' \
PATH=/bin:/usr/bin:/sbin:/usr/sbin $CMD

retval=$?

[ "$backupresolvconf" = 1 ] && {
	mv $LFS/etc/resolv.conf.tmp $LFS/etc/resolv.conf
}

unmount $LFS/dev/pts
unmount $LFS/dev
unmount $LFS/run
unmount $LFS/proc
if [ -n "$EFI_SYSTEM" ]; then
	unmount $LFS/sys/firmware/efi/efivars
fi
unmount $LFS/sys

exit $retval