#!/bin/bash
set +e
DESTDIR="$1"
if [[ $UID -ne 0 ]] ; then
    echo "You must be root!"
    exit 1
fi
if [[ -b "$1" ]] ; then
    DESTDIR=$(mktemp -d)
    mount "$1" "$DESTDIR"
fi
shift
if [[ "$DESTDIR" == "" ||  ! -f "$DESTDIR/etc/os-release" ]] ; then
    echo "Target filesystem is invalid: $DESTDIR"
    exit 1
fi
mount --bind /dev "$DESTDIR/dev"
mount --bind /run  "$DESTDIR/run"
mount --bind /media  "$DESTDIR/media"
mount -t devpts devpts "$DESTDIR/dev/pts"
mount -t sysfs sysfs "$DESTDIR/sys"
mount -t proc proc "$DESTDIR/proc"
mount -t tmpfs tmpfs  "$DESTDIR/dev/shm"
if [[ -d /sys/firmware/efi/ ]] ; then
    mount -t efivarfs efivarfs  "$DESTDIR/sys/firmware/efi/efivars"
fi
cat /etc/resolv.conf > $DESTDIR/etc/resolv.conf
SHELL=/bin/bash unshare --fork --pid chroot "$DESTDIR" "$@"
if [[ -d /sys/firmware/efi/ ]] ; then
    while umount "$DESTDIR/sys/firmware/efi/efivars" 2>/dev/null ; do : ;done
fi
for dir in dev/pts dev/shm dev sys proc run media ; do
    while umount "$DESTDIR/$dir" 2>/dev/null; do : ;done
done
umount -lf "$DESTDIR"  2>/dev/null