Mount and then enter a chroot environment

enter-chroot.sh

#!/bin/bash

set -e

if [[ -z "$1" ]]; then
  echo "Usage: $(basename $0) CHROOT_PATH"
  exit 1
fi

if [[ ${UID:-$(id -u)} == 0 ]]; then
  echo "This script must be run as a non-root user"
  exit 1
fi

CHROOT=$(realpath $1)
WHOAMI=$(whoami)
echo "CHROOT=${CHROOT}"
echo "WHOAMI=${WHOAMI}"

MOUNT_CACHE=$(echo $(awk '{print $2}' /proc/mounts))

function do_mount() {
  local src="$1"
  local args="$2"
  local path="$3"
  case " ${MOUNT_CACHE} " in
    *" ${path} "*)
      echo "Path is already mounted: ${path}"
      ;;
    *)
      echo "Mount ${path}"
      if [[ -n "${src}" ]]; then
        sudo mount -n ${args} "${src}" "${path}"
      else
        sudo mount -n ${args} "${path}"
      fi
      ;;
  esac
}

echo "Mounting directories..."
do_mount none '-t proc' ${CHROOT}/proc
do_mount none '-t sysfs' ${CHROOT}/sys
do_mount /dev '-o bind' ${CHROOT}/dev
do_mount /dev/pts '-o bind' ${CHROOT}/dev/pts

echo "Entering chroot..."
sudo chroot ${CHROOT} sudo -i -u ${WHOAMI}