image-chroot

#!/bin/bash

trap '{ stty sane; echo ""; errexit "Aborted"; }' SIGINT SIGTERM

MNTPATH="/tmp/image-chroot-mnt"

errexit()
{
  echo ""
  echo -e "$1"
  echo ""
  if [ "${MNTED}" = "TRUE" ]; then
    umount "${BOOTMNT}/" &> /dev/null
    umount "${MNTPATH}/" &> /dev/null
  fi
  rm -rf "${MNTPATH}/" &> /dev/null
  rmloop
  exit 1
}

mkloop()
{
  LOOP="$(losetup -f --show -P "${IMGFILE}")"
  if [ $? -ne 0 ]; then
    errexit "Unable to create loop device"
  fi
}

rmloop()
{
  if [ "${LOOP}" != "" ]; then
    losetup -d "${LOOP}"
    LOOP="" 
 fi
}

mntimg()
{
  mkloop
  if [ ! -d "${MNTPATH}/" ]; then
    mkdir "${MNTPATH}/"
    if [ $? -ne 0 ]; then
      errexit "Unable to make ROOT partition mount point"
    fi
  fi
  mount "${LOOP}p2" "${MNTPATH}/"
  if [ $? -ne 0 ]; then
    errexit "Unable to mount image ROOT partition"
  fi
  MNTED=TRUE
  BOOTMNT="${MNTPATH}$(sed -n '/^[[:space:]]*#/!s|^\S\+\s\+\(/boot\S*\)\s\+.*$|\1|p' "${MNTPATH}/etc/fstab")"
  if [ ! -d "${BOOTMNT}/" ]; then
    mkdir -p "${BOOTMNT}/"
    if [ $? -ne 0 ]; then
      errexit "Unable to make BOOT partition mount point"
    fi
  fi
  mount "${LOOP}p1" "${BOOTMNT}/"
  if [ $? -ne 0 ]; then
    errexit "Unable to mount image BOOT partition"
  fi
}

umntimg()
{
  umount "${BOOTMNT}/"
  if [ $? -ne 0 ]; then
    errexit "Unable to unmount image BOOT partition"
  fi
  umount "${MNTPATH}/"
  if [ $? -ne 0 ]; then
    errexit "Unable to unmount image ROOT partition"
  fi
  MNTED=FALSE
  rmloop
  rm -r "${MNTPATH}/"
}

usage()
{
  errexit "Usage: $0 [options] pathto/imagefile\n\
-h,--help       This usage description\n\
-u,--ubuntu     Ubuntu (Deprecated)"
}

LOOP=""
MNTED=FALSE
if [ $(id -u) -ne 0 ]; then
  errexit "Must be run as root user: sudo $0"
fi
PGMNAME="$(basename $0)"
for PID in $(pidof -x -o %PPID "${PGMNAME}"); do
  if [ ${PID} -ne $$ ]; then
    errexit "${PGMNAME} is already running"
  fi
done
file --version &> /dev/null
if [ $? -eq 127 ]; then
  echo ""
  echo "Installing file"
  echo ""
  apt-get update
  apt-get install file
fi
IMGFILE=""
while [ $# -gt 0 ]; do
  case "$1" in

    -h|--help)
      usage
      ;;

    -u|--ubuntu)
      shift
      ;;

    -*|--*)
      usage
      ;;

    *)
      IMGFILE="$1"
      shift
      ;;

  esac
done
if [ "${IMGFILE}" = "" ]; then
  errexit "No image file specified"
fi
if [ ! -f "${IMGFILE}" ]; then
  errexit "${IMGFILE} not found"
fi
mntimg
SYS="$(file -b /bin/bash | sed -n 's|^.*, \(ARM\s*\S*\),.*$|\1|p')"
IMG="$(file -b ${MNTPATH}/bin/bash | sed -n 's|^.*, \(ARM\s*\S*\),.*$|\1|p')"
umntimg
if [ "${SYS}" != "${IMG}" ]; then
  errexit "${IMGFILE} architecture differs from system architecture"
fi
echo ""
echo -n "chroot to ${IMGFILE} (y/n)? "
while read -r -n 1 -s answer; do
  if [[ ${answer} = [yYnN] ]]; then
    echo "${answer}"
    if [[ ${answer} = [yY] ]]; then
      break
    else
      errexit "Aborted"
    fi
  fi
done
echo ""
echo "Attempting to chroot to ${IMGFILE}"
echo "Host root filesystem is available at /host-root-fs"
echo "Use exit or ^D to terminate chroot"
echo ""
mntimg
mkdir "${MNTPATH}/host-root-fs"
mount --bind / "${MNTPATH}/host-root-fs"
mount --bind /dev "${MNTPATH}/dev"
mount --bind /sys "${MNTPATH}/sys"
mount --bind /proc "${MNTPATH}/proc"
mount --bind /dev/pts "${MNTPATH}/dev/pts"
chroot "${MNTPATH}"
umount "${MNTPATH}/dev/pts" "${MNTPATH}/proc" "${MNTPATH}/sys" "${MNTPATH}/dev"
while read MNTPT
do
  if [[ "${MNTPT}" != "${BOOTMNT}" && "${MNTPT}" != "${MNTPATH}/host-root-fs" ]]; then
    umount "${MNTPT}"
  fi
done <<< "$(findmnt -lR ${MNTPATH} | sed -n "s|^\(${MNTPATH}/\S\+\)\s\+.*$|\1|p")"
umount "${MNTPATH}/host-root-fs"
rmdir "${MNTPATH}/host-root-fs"
umntimg
echo ""
echo "Exited chroot to ${IMGFILE}"
echo ""